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  • 1.
    Andersson, Mattias L
    et al.
    Lund University, Sweden .
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Infahasaeng, Yingyot
    Lund University, Sweden .
    Tang, Zheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Yartsev, Arkady
    Lund University, Sweden .
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Sundstrom, Villy
    Lund University, Sweden .
    Unified Study of Recombination in Polymer:Fullerene Solar Cells Using Transient Absorption and Charge-Extraction Measurements2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 12, p. 2069-2072Article in journal (Refereed)
    Abstract [en]

    Recombination in the well-performing bulk heterojunction solar cell blend between the conjugated polymer TQ-1 and the substituted fullerene PCBM has been investigated with pump-probe transient absorption and charge extraction of photo-generated carriers (photo-CELIV). Both methods are shown to generate identical and overlapping data under appropriate experimental conditions. The dominant type of recombination is bimolecular with a rate constant of 7 x 10(-12) cm(-3) s(-1). This recombination rate is shown to be fully consistent with solar cell performance. Deviations from an ideal bimolecular recombination process, in this material system only observable at high pump fluences, are explained with a time-dependent charge-carrier mobility, and the implications of such a behavior for device development are discussed.

  • 2.
    Bian, Qingzhen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Abdulahi, Birhan A.
    Chalmers Univ Technol, Sweden; Addis Ababa Univ, Ethiopia; Wollo Univ, Ethiopia.
    Genene, Zewdneh
    Chalmers Univ Technol, Sweden.
    Wang, Ergang
    Chalmers Univ Technol, Sweden.
    Mammo, Wendimagegn
    Addis Ababa Univ, Ethiopia.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Reduced Nonradiative Voltage Loss in Terpolymer Solar Cells2020In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 11, no 10, p. 3796-3802Article in journal (Refereed)
    Abstract [en]

    The dissociation of hybrid local exciton and charge transfer excitons (LECT) in efficient bulk-heterojunction nonfullerene solar cells contributes to reduced nonradiative photovoltage loss, a mechanism that still remains unclear. Herein we studied the energetic and entropic contribution in the hybrid LE-CT exciton dissociation in devices based on a conjugated terpolymer. Compared with reference devices based on ternary blends, the terpolymer devices demonstrated a significant reduction in the nonradiative photovoltage loss, regardless of the acceptor molecule, be it fullerene or nonfullerene. Fourier transform photocurrent spectroscopy revealed a significant LE-CT character in the terpolymer-based solar cells. Temperature-dependent hole mobility and photovoltage confirm that entropic and energetic effects contribute to the efficient LE-CT dissociation. The energetic disorder value measured in the fullerene- or nonfullerene-based terpolymer devices suggested that this entropic contribution came from the terpolymer, a signature of higher disorder in copolymers with multiple aromatic groups. This gives new insight into the fundamental physics of efficient LE-CT exciton dissociation with smaller nonradiative recombination loss.

  • 3.
    Björk, Jonas
    et al.
    University of Liverpool, UK.
    Hanke, Felix
    University of Liverpool, UK.
    Palma, Carlos-Andres
    University de Strasbourg, France.
    Samorì, Paolo
    University de Strasbourg, France.
    Cecchini, Marco
    University de Strasbourg, France.
    Persson, Mats
    University of Liverpool, UK.
    Adsorption of Aromatic and Anti-Aromatic Systems on Graphene through π−π Stacking2010In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 1, p. 3407-3412Article in journal (Refereed)
    Abstract [en]

    The adsorption of neutral (poly)-aromatic, antiaromatic, and more generally π-conjugated systems on graphene is studied as a prototypical case of π-π stacking. To account for dispersive interactions, we compare the recent van der Waals density functional (vdw-DF) with three semiempirical corrections to density functional theory and two empirical force fields. The adsorption energies of the molecules binding to graphene predicted by the vdw-DFwere found to be in excellent agreement with temperature desorption experiments reported in litera- ture,whereas the results of theremaining functionals andforce fields only preserve the correct trends. The comparison of the dispersive versus electrostatic contribu- tions to the total binding energies in the aromatic and antiaromatic systems suggests that π-π interactions can be regarded as being prevalently dispersive in nature at large separations, whereas close to the equilibrium bonding distance, it is a complex interplay between dispersive and electrostatic Coulombic interactions. Moreover our results surprisingly indicate that the magnitude of π-π interactions normalized both per number of total atoms and carbon atoms increases signifi- cantly with the relative number of hydrogen atoms in the studied systems.

  • 4.
    Corani, Alice
    et al.
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Li, Ming-Hsien
    Department of Photonics, National Cheng Kung University, Tainan, Taiwan.
    Shen, Po-Shen
    Department of Photonics, National Cheng Kung University, Tainan, Taiwan.
    Chen, Peter
    Department of Photonics, National Cheng Kung University, Tainan, Taiwan; Advanced Optoelectronic Technology Center (AOTC), Tainan, Taiwan; Research Center for Energy Technology and Strategy (RCETS), Tainan, Taiwan.
    Guo, Tzung-Fang
    Department of Photonics, National Cheng Kung University, Tainan, Taiwan; Advanced Optoelectronic Technology Center (AOTC), Tainan, Taiwan; Research Center for Energy Technology and Strategy (RCETS), Tainan, Taiwan.
    El Nahhas, Aural
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Zheng, Kaibo
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Yartsev, Arkady
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Sundstrom, Villy
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Ponseca, Jr., Carlito S.
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Ultrafast Dynamics of Hole Injection and Recombination in Organometal Halide Perovskite Using Nickel Oxide as p-Type Contact Electrode2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 7, p. 1096-1101Article in journal (Refereed)
    Abstract [en]

    There is a mounting effort to use nickel oxide (NiO) as p-type selective electrode for organometal halide perovskite-based solar cells. Recently, an overall power conversion efficiency using this hole acceptor has reached 18%. However, ultrafast spectroscopic investigations on the mechanism of charge injection as well as recombination dynamics have yet to be studied and understood. Using time-resolved terahertz spectroscopy, we show that hole transfer is complete on the subpicosecond time scale, driven by the favorable band alignment between the valence bands of perovskite and NiO nanoparticles (NiO(np)). Recombination time between holes injected into NiO(np)) and mobile electrons in the perovskite material is shown to be hundreds of picoseconds to a few nanoseconds. Because of the low conductivity of NiO(np)) holes are pinned at the interface, and it is electrons that determine the recombination rate. This recombination competes with charge collection and therefore must be minimized. Doping NiO to promote higher mobility of holes is desirable in order to prevent back recombination.

  • 5.
    Di Meo, Florent
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology.
    Pedersen, Morten
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. University of Southern Denmark, Denmark.
    Rubio-Magnieto, Jenifer
    University of Mons UMONS, Belgium.
    Surin, Mathieu
    University of Mons UMONS, Belgium.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology. University of Mons UMONS, Belgium.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology.
    DNA Electronic Circular Dichroism on the Inter-Base Pair Scale: An Experimental Theoretical Case Study of the AT Homo-Oligonucleotide2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 3, p. 355-359Article in journal (Refereed)
    Abstract [en]

    A successful elucidation of the near-ultraviolet electronic circular dichroism spectrum of a short double-stranded DNA is reported. Time-dependent density functional theory methods are shown to accurately predict spectra and assign bands on the microscopic base-pair scale, a finding that opens the field for using circular dichroism spectroscopy as a sensitive nanoscale probe of DNA to reveal its complex interactions with the environment.

  • 6.
    Fahleson, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Ågren, Hans
    KTH Royal Institute Technology, Sweden.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering. KTH Royal Institute Technology, Sweden.
    A Polarization Propagator for Nonlinear X-ray Spectroscopies2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 11, p. 1991-1995Article in journal (Refereed)
    Abstract [en]

    A complex polarization propagator approach has been developed to third order and implemented in density functional theory (DFT), allowing for the direct calculation of nonlinear molecular properties in the X-ray wavelength regime without explicitly addressing the excited-state manifold. We demonstrate the utility of this propagator method for the modeling of coherent near-edge X-ray two-photon absorption using, as an example, DFT as the underlying electronic structure model. Results are compared with the corresponding near edge X-ray absorption fine structure spectra, illuminating the differences in the role of symmetry, localization, and correlation between the two spectroscopies. The ramifications of this new technique for nonlinear X-ray research are briefly discussed.

  • 7.
    Felekidis, Nikolaos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Melianas, A.
    Stanford Univ, CA 94305 USA.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    The Role of Delocalization and Excess Energy in the Quantum Efficiency of Organic Solar Cells and the Validity of Optical Reciprocity Relations2020In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 11, no 9, p. 3563-3570Article in journal (Refereed)
    Abstract [en]

    The photon energy dependence of long-range charge separation is studied for two prototypical polymer:fullerene systems. The internal quantum efficiency (IQE) of PCDTBT:PC61BM is experimentally shown to be independent of the excitation energy. In contrast, for TQ1:PC71BM the IQE is strongly energy-dependent for excitation energies close to charge transfer (CT) electroluminescence peak maximum while it becomes energy-independent at higher excitation energies. Kinetic Monte Carlo simulations reproduce the experimental IQE and reveal that the photon energy-dependence of the IQE is governed by charge delocalization. Efficient long-range separation at excitation energies corresponding to the CT electroluminescence peak maximum or lower requires an initial separation of the hole- electron pair by similar to 4-5 nm, whereas delocalization is less important for charge separation at higher photon energies. Our modeling results suggest that a phenomenological reciprocity between CT electroluminescence and external quantum efficiency does not necessarily prove that commonly employed reciprocity relations between these spectra are valid from a fundamental perspective.

  • 8.
    Gervilla, Víctor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Zarshenas, Mohammad
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Anomalous versus Normal Room-Temperature Diffusion of Metal Adatoms on Graphene2020In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, The Journal of Physical Chemistry Letters, Vol. 11, no 21, p. 8930-8936Article in journal (Refereed)
    Abstract [en]

    Fabrication of high-performance heterostructure devices requires fundamental understanding of the diffusion dynamics of metal species on 2D materials. Here, we investigate the room-temperature diffusion of Ag, Au, Cu, Pd, Pt, and Ru adatoms on graphene using ab initio and classical molecular dynamics simulations. We find that Ag, Au, Cu, and Pd follow Lévy walks, in which adatoms move continuously within ∼1–4 nm2 domains during ∼0.04 ns timeframes, and they occasionally perform ∼2–4 nm flights across multiple surface adsorption sites. This anomalous diffusion pattern is associated with a flat (<50 meV) potential energy landscape (PEL), which renders surface vibrations important for adatom migration. The latter is not the case for Pt and Ru, which encounter a significantly rougher PEL (>100 meV) and, hence, migrate via conventional random walks. Thus, adatom anomalous diffusion is a potentially important aspect for modeling growth of metal films and nanostructures on 2D materials.

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  • 9.
    Hao, Zhengming
    et al.
    Soochow Univ, Peoples R China.
    Peng, Guyue
    Soochow Univ, Peoples R China.
    Wang, Lina
    Soochow Univ, Peoples R China.
    Li, Xuechao
    Soochow Univ, Peoples R China.
    Liu, Ye
    Soochow Univ, Peoples R China.
    Xu, Chaojie
    Soochow Univ, Peoples R China.
    Niu, Kaifeng
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering. Soochow Univ, Peoples R China.
    Ding, Honghe
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Hu, Jun
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Zhang, Liang
    Soochow Univ, Peoples R China.
    Dong, Bin
    Soochow Univ, Peoples R China.
    Zhang, Haiming
    Soochow Univ, Peoples R China.
    Zhu, Junfa
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China.
    Converting n-Alkanol to Conjugated Polyenal on Cu(110) Surface at Mild Temperature2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 14, p. 3276-3282Article in journal (Refereed)
    Abstract [en]

    Achieving C(sp(3))-H activation at a mild temperature is of great importance from both scientific and technologic points of view. Herein, on the basis of the on-surface synthesis strategy, we report the significant reduction of the C(sp(3))-H activation barrier, which results in the full C(sp(3))-H to C(sp(2))-H transformation of n-alkanol (octacosan-1-ol) at a mild temperature as low as 350 K on the Cu(110) surface, yielding the conjugated polyenal (octacosa-tridecaenal) as the final product. The reaction mechanism is revealed by the combined scanning tunneling microscope, density functional theory, and synchrotron radiation photoemission spectroscopy.

  • 10.
    Karuthedath, Safakath
    et al.
    KAUST, Saudi Arabia.
    Gorenflot, Julien
    KAUST, Saudi Arabia.
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kan, Zhipeng
    KAUST, Saudi Arabia.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Laquai, Frederic
    KAUST, Saudi Arabia.
    Buildup of Triplet-State Population in Operating TQ1:PC71BM Devices Does Not Limit Their Performance2020In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 11, no 8, p. 2838-2845Article in journal (Refereed)
    Abstract [en]

    Triplet generation in organic solar cells has been considered a major loss channel. Determining the density of the triplet-state population in an operating device is challenging. Here, we employ transient absorption (TA) spectroscopy on the quinoxaline-thiophene copolymer TQ1 blended with PC71BM, quantify the transient charge and tripletstate densities, and parametrize their generation and recombination dynamics. The charge recombination parameters reproduce the experimentally measured current-voltage characteristics in charge carrier drift-diffusion simulations, and they yield the steady-state charge densities. We demonstrate that triplets are formed by both geminate and nongeminate recombination of charge carriers and decay primarily by triplet-triplet annihilation. Using the charge densities in the rate equations describing triplet-state dynamics, we find that triplet-state densities in devices are in the range of charge carrier densities. Despite this substantial triplet-state buildup, TQ1:PC71BM devices exhibit only moderate geminate recombination and significantly reduced nongeminate charge recombination, with reduction factors between 10(-4) and 10(-3) compared to Langevin recombination.

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  • 11.
    Ke, You
    et al.
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Wang, Nana
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Kong, Decheng
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Cao, Yu
    Nanjing Tech Univ NanjingTech, Peoples R China.
    He, Yarong
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Zhu, Lin
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Xue, Chen
    Northwestern Polytech Univ, Peoples R China.
    Peng, Qiming
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Huang, Wei
    Nanjing Tech Univ NanjingTech, Peoples R China; Northwestern Polytech Univ, Peoples R China.
    Wang, Jianpu
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Defect Passivation for Red Perovskite Light-Emitting Diodes with Improved Brightness and Stability2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 3, p. 380-385Article in journal (Refereed)
    Abstract [en]

    Efficient and stable red perovskite light-emitting diodes (PeLEDs) are important for realizing full-color display and lighting. Red PeLEDs can be achieved either by mixed-halide or low-dimensional perovskites. However, the device performance, especially the brightness, is still low owing to phase separation or poor charge transport issues. Here, we demonstrate red PeLEDs based on three-dimensional (3D) mixed-halide perovskites where the defects are passivated by using 5-aminovaleric acid. The red PeLEDs with an emission peak at 690 nm exhibit an external quantum efficiency of 8.7% and a luminance of 1408 cd m(-2). A maximum luminance of 8547 cd m(-2) can be further achieved as tuning the emission peak to 662 nm, representing the highest brightness of red PeLEDs. Moreover, those LEDs exhibit a half-life of up to 8 h under a high constant current density of 100 mA cm(-2), which is over 10 times improvement compared to literature results.

  • 12.
    Li, Youbing
    et al.
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Zhu, Shuairu
    Tianjin Univ, Peoples R China.
    Wu, Erxiao
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Ding, Haoming
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mu, Xulin
    Beijing Univ Technol, Peoples R China.
    Chen, Lu
    Chinese Acad Sci, Peoples R China; Qianwan Institute of CNiTECH, Peoples R China.
    Zhang, Yiming
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Chen, Ke
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Li, Mian
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Yan, Pengfei
    Beijing Univ Technol, Peoples R China.
    Persson, Per O Å
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Du, Shiyu
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Kuang, Yongbo
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Chai, Zhifang
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Huang, Qing
    Chinese Acad Sci, Peoples R China; Qianwan Inst CNiTECH, Peoples R China.
    Nanolaminated Ternary Transition Metal Carbide (MAX Phase)-Derived Core-Shell Structure Electrocatalysts for Hydrogen Evolution and Oxygen Evolution Reactions in Alkaline Electrolytes2023In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 14, no 2, p. 481-488Article in journal (Refereed)
    Abstract [en]

    The development of abundant, cheap, and highly active catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important for hydrogen production. Nanolaminate ternary transition metal carbides (MAX phases) and their derived two-dimensional transition metal carbides (MXenes) have attracted considerable interest for electrocatalyst applications. Herein, four new MAX@MXene core-shell structures (Ta2CoC@ Ta2CTx, Ta2NiC@Ta2CTx, Nb2CoC@Nb2CTx, and Nb2NiC@Nb2CTx), in which the core region is Co/Ni-MAX phases while the edge region is MXenes, have been prepared. Under alkaline electrolyte conditions, the Ta2CoC@Ta2CTx core-shell structure showed an overpotential of 239 mV and excellent stability during the HER with MXenes as the active sites. For the OER, the Ta2CoC@Ta2CTx core- shell structure showed an overpotential of 373 mV and a small Tafel plot (56 mV dec-1), which maintained a bulk crystalline structure and generated Co-based oxyhydroxides that formed by surface reconstruction as active sites. Considering rich chemical compositions and structures of MAX phases, this work provides a new strategy for designing multifunctional electrocatalysts and also paves the way for further development of MAX phase-based materials for clean energy applications.

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  • 13.
    Liu, Yanfeng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Jiaxing Univ, Peoples R China.
    Fan, Qunping
    Chalmers Univ Technol, Sweden; Xi An Jiao Tong Univ, Peoples R China.
    Liu, Heng
    Chinese Univ Hong Kong, Peoples R China.
    Jalan, Ishita
    Karlstad Univ, Sweden.
    Jin, Yingzhi
    Jiaxing Univ, Peoples R China.
    van Stam, Jan
    Karlstad Univ, Sweden.
    Moons, Ellen
    Karlstad Univ, Sweden.
    Wang, Ergang
    Chalmers Univ Technol, Sweden.
    Lu, Xinhui
    Chinese Univ Hong Kong, Peoples R China.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    In Situ Optical Spectroscopy Demonstrates the Effect of Solvent Additive in the Formation of All-Polymer Solar Cells2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 50, p. 11696-11702Article in journal (Refereed)
    Abstract [en]

    1-Chloronaphthalene (CN) has been a common solvent additive in both fullerene-and nonfullerene-based organic solar cells. In spite of this, its working mechanism is seldom investigated, in particular, during the drying process of bulk heterojunctions composed of a donor:acceptor mixture. In this work, the role of CN in all-polymer solar cells is investigated by in situ spectroscopies and ex situ characterization of blade-coated PBDB-T:PF5-Y5 blends. Our results suggest that the added CN promotes self-aggregation of polymer donor PBDB-T during the drying process of the blend film, resulting in enhanced crystallinity and hole mobility, which contribute to the increased fill factor and improved performance of PBDB-T:PF5-Y5 solar cells. Besides, the nonradiative energy loss of the corresponding device is also reduced by the addition of CN, corresponding to a slightly increased open-circuit voltage. Overall, our observations deepen our understanding of the drying dynamics, which may guide further development of all-polymer solar cells.

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  • 14.
    Liu, Xiaoke
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Organic-Inorganic Hybrid Ruddlesden-Popper Perovskites: An Emerging Paradigm for High-Performance Light-Emitting Diodes2018In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 9, no 9, p. 2251-2258Article in journal (Refereed)
    Abstract [en]

    Recently, lead halide perovskite materials have attracted extensive interest, in particular, in the research field of solar cells. These materials are fascinating "soft" materials with semiconducting properties comparable to the best inorganic semiconductors like silicon and gallium arsenide. As one of the most promising perovskite family members, organic-inorganic hybrid Ruddlesden-Popper perovskites (HRPPs) offer rich chemical and structural flexibility for exploring excellent properties for optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). In this Perspective, we present an overview of HRPPs on their structural characteristics, synthesis of pure HRPP compounds and thin films, control of their preferential orientations, and investigations of heterogeneous HRPP thin films. Based on these recent advances, future directions and prospects have been proposed. HRPPs are promising to open up a new paradigm for high-performance LEDs.

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  • 15.
    Nadhom, Hama
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Rouf, Polla
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Area Selective Deposition of Metals from the Electrical Resistivity of the Substrate2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, The Journal of Physical Chemistry Letters, Vol. 12, no 17, p. 4130-4133Article in journal (Refereed)
    Abstract [en]

    Area selective deposition (ASD) of films only on desired areas of the substrate opens for less complex fabrication of nanoscaled electronics. We show that a newly developed CVD method, where plasma electrons are used as the reducing agent in deposition of metallic thin films, is inherently area selective from the electrical resistivity of the substrate surface. When depositing iron with the new CVD method, no film is deposited on high-resistivity SiO2 surfaces whereas several hundred nanometers thick iron films are deposited on areas with low resistivity, obtained by adding a thin layer of silver on the SiO2 surface. On the basis of such a scheme, we show how to use the electric resistivity of the substrate surface as an extension of the ASD toolbox for metal-on-metal deposition.

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  • 16.
    Niu, Kaifeng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering. Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering.
    Termination-Accelerated Electrochemical Nitrogen Fixation on Single-Atom Catalysts Supported by MXenes2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 12, p. 2800-2807Article in journal (Refereed)
    Abstract [en]

    The synthesis of ammonia (NH3) from nitrogen (N2) under ambientconditions is of great significance but hindered by the lack of highly efficient catalysts. Byperformingfirst-principles calculations, we have investigated the feasibility for employing atransition metal (TM) atom, supported on Ti3C2T2MXene with O/OH terminations, as asingle-atom catalyst (SAC) for electrochemical nitrogen reduction. The potential catalyticperformance of TM single atoms is evaluated by their adsorption behavior on the MXene,together with their ability to bind N2and to desorb NH3molecules. Of importance, the OHterminations on Ti3C2T2MXene can effectively enhance the N2adsorption and decrease theNH3adsorption for single atoms. Based on proposed criteria for promising SACs, ourcalculations further demonstrate that the Ni/Ti3C2O0.19(OH)1.81exhibits reasonablethermodynamics and kinetics toward electrochemical nitrogen reduction.

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  • 17.
    Pavliuk, Mariia V.
    et al.
    Physical Chemistry Division, Department of Chemistry, Ångstrom Laboratory, Uppsala University, Uppsala, Sweden.
    Gutierrez Alvarez, Sol
    Physical Chemistry Division, Department of Chemistry, Ångstrom Laboratory, Uppsala University, Uppsala, Sweden.
    Hattori, Yocefu
    Physical Chemistry Division, Department of Chemistry, Ångstrom Laboratory, Uppsala University, Uppsala, Sweden.
    Messing, Maria E.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Czapla-Masztafiak, Joanna
    Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland.
    Szlachetko, Jakub
    Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland; Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.
    Silva, Jose Luis
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Araujo, Carlos Moyses
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    A. Fernandes, Daniel L.
    Physical Chemistry Division, Department of Chemistry, Ångstrom Laboratory, Uppsala University, Uppsala, Sweden.
    Lu, Li
    Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, Pennsylvania United States.
    Kiely, Christopher J.
    Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, Pennsylvania United States.
    Abdellah, Mohamed
    Physical Chemistry Division, Department of Chemistry, Ångstrom Laboratory, Uppsala University, Uppsala, Sweden; Department of Chemistry, Qena Faculty of Science, South Valley University, Qena, Egypt.
    Nordlander, Peter
    Department of Physics, Rice University, Houston, Texas United States.
    Sá, Jacinto
    Physical Chemistry Division, Department of Chemistry, Ångstrom Laboratory, Uppsala University, Uppsala, Sweden; Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.
    Hydrated Electron Generation by Excitation of Copper Localized Surface Plasmon Resonance2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 8, p. 1743-1749Article in journal (Refereed)
    Abstract [en]

    Hydrated electrons are important in radiation chemistry and charge-transfer reactions, with applications that include chemical damage of DNA, catalysis, and signaling. Conventionally, hydrated electrons are produced by pulsed radiolysis, sonolysis, two-ultraviolet-photon laser excitation of liquid water, or photodetachment of suitable electron donors. Here we report a method for the generation of hydrated electrons via single-visible-photon excitation of localized surface plasmon resonances (LSPRs) of supported sub-3 nm copper nanoparticles in contact with water. Only excitations at the LSPR maximum resulted in the formation of hydrated electrons, suggesting that plasmon excitation plays a crucial role in promoting electron transfer from the nanoparticle into the solution. The reactivity of the hydrated electrons was confirmed via proton reduction and concomitant H2 evolution in the presence of a Ru/TiO2 catalyst.

  • 18.
    Piatkowski, Piotr
    et al.
    Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, Sin Número, 45071 Toledo, Spain.
    Cohen, Boiko
    Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, Sin Número, 45071 Toledo, Spain.
    Ponseca, Carlito S.
    Division of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden.
    Salado, Manuel
    Abengoa Research, Abengoa, Campus Palmas Altas, C/Energia Solar, 41014 Sevilla, Spain.
    Kazim, Samrana
    Abengoa Research, Abengoa, Campus Palmas Altas, C/Energia Solar, 41014 Sevilla, Spain.
    Ahmad, Shahzada
    Abengoa Research, Abengoa, Campus Palmas Altas, C/Energia Solar, 41014 Sevilla, Spain.
    Sundström, Villy
    Division of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden.
    Douhal, Abderrazzak
    Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica, and INAMOL, Universidad de Castilla-La Mancha, Avenida Carlos III, Sin Número, 45071 Toledo, Spain.
    Unraveling charge carriers generation, diffusion, and recombination in formamidinium lead triiodide perovskite polycrystalline thin film2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, p. 204-210Article in journal (Refereed)
    Abstract [en]

    We report on studies of the formamidinium lead triiodide (FAPbI3) perovskite film using time-resolved terahertz (THz) spectroscopy (TRTS) and flash photolysis to explore charge carriers generation, migration, and recombination. The TRTS results show that upon femtosecond excitation above the absorption edge, the initial high photoconductivity (∼75 cm2 V–1 s–1) remains constant at least up to 8 ns, which corresponds to a diffusion length of 25 μm. Pumping below the absorption edge results in a mobility of 40 cm2 V–1 s–1 suggesting lower mobility of charge carriers located at the bottom of the conduction band or shallow sub-bandgap states. Furthermore, analysis of the THz kinetics reveals rising components of <1 and 20 ps, reflecting dissociation of excitons having different binding energies. Flash photolysis experiments indicate that trapped charge carriers persist for milliseconds. 

  • 19.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Moro, Fabrizio
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Höjer, Pontus
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ning, Weihua
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Effect of Crystal Symmetry on the Spin States of Fe3+ and Vibration Modes in Lead-free Double-Perovskite Cs2AgBi(Fe)Br-62020In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 11, no 12, p. 4873-4878Article in journal (Refereed)
    Abstract [en]

    We show by electron spin resonance (ESR) and Raman spectroscopies that the crystal phase transition of the lead-free double-perovskite Cs2AgBiBr6 has a profound symmetry-breaking effect on the high spin states of, for example, a transition-metal ion Fe3+ and the vibrational modes. It lifts their degeneracy when the crystal undergoes the cubic-tetragonal phase transition, splitting the six-fold degenerate S = 5/2 state of Fe3+ to three Kramer doublets and the enharmonic breathing mode T-g of the MBr6 octahedra (M = Ag, Bi, Fe) into E-g + A(g). The magnitudes of both spin and Raman line splitting are shown to directly correlate with the strength of the tetragonal strain field. This work, in turn, demonstrates the power of the ESR and Raman spectroscopies in probing structural phase transitions and in providing in-depth information on the interplay between the structural, spin, and vibrational properties of lead-free double perovskites, a newly emerging and promising class of materials for low-cost and high-efficiency photovoltaics and optoelectronics.

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  • 20.
    Ribeiro, Luiz Antonio
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology.
    Ferreira da Cunha, Wiliam
    University of Brasilia, Brazil.
    Luciano de Almeida Fonseca, Antonio
    University of Brasilia, Brazil.
    Magela e Silva, Geraldo
    University of Brasilia, Brazil.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology.
    Transport of Polarons in Graphene Nanoribbons2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 3, p. 510-514Article in journal (Refereed)
    Abstract [en]

    The field-induced dynamics of polarons in armchair graphene nanoribbons (GNRs) is theoretically investigated in the framework of a two-dimensional tight-binding model with lattice relaxation. Our findings show that the semiconductor behavior, fundamental to polaron transport to take place, depends upon of a suitable balance between the GNR width and the electronphonon (eph) coupling strength. In a similar way, we found that the parameter space for which the polaron is dynamically stable is limited to an even narrower region of the GNR width and the eph coupling strength. Interestingly, the interplay between the external electric field and the eph coupling plays the role to define a phase transition from subsonic to supersonic velocities for polarons in GNRs.

  • 21.
    Roland, Steffen
    et al.
    Univ Potsdam, Germany; UP Transfer GmbH, Germany.
    Kniepert, Juliane
    Univ Potsdam, Germany.
    Love, John A.
    Univ Potsdam, Germany.
    Negi, Vikas
    Eindhoven Univ Technol, Netherlands.
    Liu, Feilong
    Eindhoven Univ Technol, Netherlands.
    Bobbert, Peter
    Eindhoven Univ Technol, Netherlands.
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Stanford Univ, CA 94305 USA.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Hofacker, Andreas
    Tech Univ Dresden, Germany.
    Neher, Dieter
    Univ Potsdam, Germany.
    Equilibrated Charge Carrier Populations Govern Steady-State Nongeminate Recombination in Disordered Organic Solar Cells2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 6, p. 1374-1381Article in journal (Refereed)
    Abstract [en]

    We employed bias-assisted charge extraction techniques to investigate the transient and steady-state recombination of photogenerated charge carriers in complete devices of a disordered polymer-fullerene blend. Charge recombination is shown to be dispersive, with a significant slowdown of the recombination rate over time, consistent with the results from kinetic Monte Carlo simulations. Surprisingly, our experiments reveal little to no contributions from early time recombination of nonequilibrated charge carriers to the steady-state recombination properties. We conclude that energetic relaxation of photogenerated carriers outpaces any significant nongeminate recombination under application-relevant illumination conditions. With equilibrated charges dominating the steady-state recombination, quasi-equilibrium concepts appear suited for describing the open-circuit voltage of organic solar cells despite pronounced energetic disorder.

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  • 22.
    Rybicka-Jasinska, Katarzyna
    et al.
    Univ Calif Riverside, CA 92521 USA; Polish Acad Sci, Poland.
    Espinoza, Eli M.
    Univ Calif Riverside, CA 92521 USA; Univ Calif Berkeley, CA 94720 USA.
    Clark, John A.
    Univ Calif Riverside, CA 92521 USA.
    Derr, James B.
    Univ Calif Riverside, CA 92521 USA; Univ Texas Austin, TX 78712 USA.
    Carlos, Gregory
    Univ Calif Riverside, CA 92521 USA.
    Morales, Maryann
    Univ Calif Riverside, CA 92521 USA; CALTECH, CA 91125 USA.
    Billones, Mimi Karen
    Univ Calif Riverside, CA 92521 USA; Univ 452 Calif, CA 92521 USA.
    OMari, Omar
    Univ Calif Riverside, CA 92521 USA.
    Agren, Hans
    Uppsala Univ, Sweden.
    Baryshnikov, Glib
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Vullev, Valentine I
    Univ Calif Riverside, CA 92521 USA; Univ Calif Riverside, CA 92521 USA; Univ Calif Riverside, CA 92521 USA; Univ Calif Riverside, CA 92521 USA.
    Making Nitronaphthalene Fluoresce2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 42, p. 10295-10303Article in journal (Refereed)
    Abstract [en]

    Nitroaromatic compounds are inherently nonfluorescent, and the subpico-second lifetimes of the singlet excited states of many small nitrated polycyclic aromatic hydrocarbons, such as nitronaphthalenes, render them unfeasible for photosensitizers and photo-oxidants, despite their immensely beneficial reduction potentials. This article reports up to a 7000-fold increase in the singlet-excited-state lifetime of 1-nitronaphthalene upon attaching an amine or an N-amide to the ring lacking the nitro group. Varying the charge-transfer (CT) character of the excited states and the medium polarity balances the decay rates along the radiative and the two nonradiative pathways and can make these nitronaphthalene derivatives fluoresce. The strong electron-donating amine suppresses intersystem crossing (ISC) but accommodates CT pathways of nonradiate deactivation. Conversely, the N-amide does not induce a pronounced CT character but slows down ISC enough to achieve relatively long lifetimes of the singlet excited state. These paradigms are key for the pursuit of electron-deficient (n-type) organic conjugates with promising optical characteristics.

  • 23.
    Santoro, Fabrizio
    et al.
    Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Italy .
    Improta, Roberto
    Istituto di Chimica dei Composti Organometallici (ICCOM-CNR).
    Fahleson, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Coriani, Sonia
    Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Italy .
    Relative Stability of the L-a and L-b Excited States in Adenine and Guanine: Direct Evidence from TD-DFT Calculations of MCD Spectra2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 11, p. 1806-1811Article in journal (Refereed)
    Abstract [en]

    The relative position of L-a and L-b pi pi* electronic states in purine nucleobases is a much debated topic, since it can strongly affect our understanding of their photoexcited dynamics. To assess this point, we calculated the absorption and magnetic circular dichroism (MCD) spectra of adenine, guanine, and their nucleosides in gas-phase and aqueous solution,. exploiting recent developments in MCD computational technology within time-dependent density functional theory. MCD spectroscopy allows us to resolve the intense S-0 -greater than L-a transition from the weak S-0 -greater than L-b transition. The spectra obtained in water solution, by using B3LYP and CAM-B3LYP functionals and describing solvent effect by cluster models and by the polarizable continuum model (PCM), are in very good agreement with the experimental counterparts, thus providing direct and unambiguous evidence that the energy ordering predicted by TD-DFT, L-a less than L-b, is the correct one.

  • 24.
    Shah, Jalil
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sohail, Hafiz Muhammad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Uhrberg, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Wang, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Two-Dimensional Binary Honeycomb Layer Formed by Ag and Te on Ag(111)2020In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 11, no 5, p. 1609-1613Article in journal (Refereed)
    Abstract [en]

    Inspired by the unique properties of graphene, research efforts have broadened to investigations of various other two-dimensional materials with the aim of exploring their properties for future applications. Our combined experimental and theoretical study confirms the existence of a binary honeycomb structure formed by Ag and Te on Ag(111). Low-energy electron diffraction shows sharp spots which provide evidence of an undistorted AgTe layer. Band structure data obtained by angle-resolved photoelectron spectroscopy are closely reproduced by first-principles calculations, using density functional theory (DFT). This confirms the formation of a honeycomb structure with one Ag and one Te atom in the unit cell. In addition, the theoretical band structure reproduces also the finer details of the experimental bands, such as a split of one of the AgTe bands.

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  • 25.
    Silva, Jose Luis
    et al.
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Unger, Isaak
    Molecular and Condensed Matter Physics Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Matias, Tiago Araujo
    Department of Fundamental Chemistry, Institute of Chemistry, University of Sã o Paulo, Av. Lineu Prestes 748, Cidade Universitária, Butanta, Sao Paulo, Brazil.
    Franco, Leandro Rezende
    Instituto de Física, Universidade de São Paulo, Cidade Universitária, São Paulo, SP, Brazil.
    Damas, Giane
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Costa, Luciano T.
    Instituto de Química, Departamento de Físico-química, Universidade Federal Fluminense, Outeiro de São Joã o Batista Niterói, RJ, Brazil.
    Toledo, Kalil C. F.
    Department of Fundamental Chemistry, Institute of Chemistry, University of Sã o Paulo, Av. Lineu Prestes 748, Cidade Universitária, Butanta, Sao Paulo, Brazil.
    Rocha, Tulio C. R.
    Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research on Energy and Materials (CNPEM), Campinas, SP, Brazil.
    de Brito, Arnaldo Naves
    Institute of Physics “Gleb Wataghin”, University of Campinas, Campinas, SP, Brazil.
    Saak, Clara-Magdalena
    Molecular and Condensed Matter Physics Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Coutinho, Kaline
    Instituto de Física, Universidade de São Paulo, Cidade Universitária, São Paulo, SP, Brazil.
    Araki, Koiti
    Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Cidade Universitária, Butanta, Sao Paulo, Brazil.
    Björneholm, Olle
    Molecular and Condensed Matter Physics Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Brena, Barbara
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Araujo, C. Moyses
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    X-ray Photoelectron Fingerprints of High-Valence Ruthenium–Oxo Complexes along the Oxidation Reaction Pathway in an Aqueous Environment2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 24, p. 7636-7643Article in journal (Refereed)
    Abstract [en]

    Recent advances in operando-synchrotron-based X-ray techniques are making it possible to address fundamental questions related to complex proton-coupled electron transfer reactions, for instance, the electrocatalytic water splitting process. However, it is still a grand challenge to assess the ability of the different techniques to characterize the relevant intermediates, with minimal interference on the reaction mechanism. To this end, we have developed a novel methodology employing X-ray photoelectron spectroscopy (XPS) in connection with the liquid-jet approach to probe the electrochemical properties of a model electrocatalyst, [RuII(bpy)2(py)(OH2)]2+, in an aqueous environment. There is a unique fingerprint of the extremely important higher-valence ruthenium–oxo species in the XPS spectra along the oxidation reaction pathway. Furthermore, a sequential method combining quantum mechanics and molecular mechanics is used to illuminate the underlying physical chemistry of such systems. This study provides the basis for the future development of in-operando XPS techniques for water oxidation reactions.

  • 26.
    Song, Luying
    et al.
    Soochow Univ, Peoples R China.
    Yang, Biao
    Soochow Univ, Peoples R China; Tech Univ Munich, Germany.
    Fan, Xing
    Soochow Univ, Peoples R China.
    Mao, Yahui
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Shan, Huan
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Wang, Junbo
    Soochow Univ, Peoples R China.
    Niu, Kaifeng
    Linköping University, Department of Physics, Chemistry and Biology, Materials design. Linköping University, Faculty of Science & Engineering. Soochow Univ, Peoples R China.
    Hao, Zhengming
    Soochow Univ, Peoples R China.
    Zeng, Zhiwen
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China.
    Li, Youyong
    Soochow Univ, Peoples R China.
    Zhao, Aidi
    Univ Sci & Technol China, Peoples R China; Univ Sci & Technol China, Peoples R China; ShanghaiTech Univ, Peoples R China.
    Lin, Haiping
    Shaanxi Normal Univ, Peoples R China.
    Chi, Lifeng
    Soochow Univ, Peoples R China.
    Li, Qing
    Shaanxi Normal Univ, Peoples R China.
    Intra- and Inter-Self-Assembly of Identical Supramolecules on Silver Surfaces2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 38, p. 8902-8907Article in journal (Refereed)
    Abstract [en]

    Self-assembly of identical organometallic supra -molecules into ordered superstructures is of great interest in both chemical science and nanotechnology due to its potential to generate neoteric properties through collective effects. In this work, we demonstrate that large-scale self-organization of atomically precise organometallic supramolecules can be achieved through cascaded on-surface chemical reactions, by the combination of intra-and inter-supramolecular interactions. Supramolecules with defined size and shape are first built through intramolecular reaction and intermolecular metal coordination, followed by the formation of well-ordered two-dimensional arrays with the assistance of Br atoms by-C-HmiddotmiddotmiddotBr interactions. The mechanism of this process has been investigated from the perspectives of thermodynamics and kinetics.

  • 27.
    Suresh, Rahul
    et al.
    Siberian Fed Univ, Russia.
    Baryshnikov, Glib
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kuklin, Artem V
    Uppsala Univ, Sweden.
    Nemkova, Diana I
    Siberian Fed Univ, Russia; Siberian Fed Univ, Russia.
    Saikova, Svetlana V
    Siberian Fed Univ, Russia.
    Ågren, Hans
    Uppsala Univ, Sweden.
    Cyclo[18]carbon Formation from C(18)Br(6) and C18(CO)(6) Precursors2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 44, p. 10318-10325Article in journal (Refereed)
    Abstract [en]

    Although cyclo[18]carbon has been isolated experimentally from two precursors, C18Br6 and C-18(CO)(6), no reaction mechanisms have yet been explored. Herein, we provide insight into the mechanism behind debromination and decarbon-ylation. Both neutral precursors demonstrate high activation barriers of similar to 2.3 eV, while the application of an electric field can lower the barriers by 0.1-0.2 eV. The barrier energy of the anion-radicals is found to be significantly lower for C18Br6 compared to C-18(CO)(6), confirming a considerably higher yield of cylco[18] carbon when the C18Br6 precursor is used. Elongation of the C-Br bond in the anion-radical confirms its predissociation condition. Natural bonding orbital analysis shows that the stability of C-Br and C-CO bonds in the anion-radicals is lower compared to their neutral species, indicating a possible higher yield. The applied analysis provides crucial details regarding the reaction yield of cyclo[18]carbon and can serve as a general scheme for tuning reaction conditions for other organic precursors.

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  • 28.
    Tress, Wolfgang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Swiss Federal Institute Technology EPFL, Switzerland.
    Beyer, Beatrice
    Fraunhofer Institute Electron Beam Plasma Technology and CO, Germany.
    Ashari Astani, Negar
    Ecole Polytech Federal Lausanne, Switzerland.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Meloni, Simone
    Ecole Polytech Federal Lausanne, Switzerland.
    Rothlisberger, Ursula
    Ecole Polytech Federal Lausanne, Switzerland.
    Extended Intermolecular Interactions Governing Photocurrent-Voltage Relations in Ternary Organic Solar Cells2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 19, p. 3936-3944Article in journal (Refereed)
    Abstract [en]

    Efficient organic solar cells are based on (electron) donor-acceptor heterojunctions. An optically generated excited molecular state (exciton) is dissociated at this junction, forming a charge-transfer (CT) state in an intermediate step before the electron and hole are completely separated. The observed highly efficient dissociation of this Coulombically bound state raises the question on the dissociation mechanism. Here, we show that the observed high quantum yields of charge carrier generation and CT state dissociation are due to extended (and consequently weakly bound) CT states visible in absorption and emission spectra and first-principles calculations. Identifying a new geminate-pair loss mechanism via donor excimers, we find that the hole on the small-molecule donor is not localized on a single molecule and charge separation is correlated with the energetic offset between excimer and CT states. Thus, the charges upon interface charge transfer and even in the case of back-transfer and recombination are less localized than commonly assumed.

  • 29.
    Upreti, Tanvi
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Tormann, Constantin
    Heidelberg Univ, Germany.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Can Organic Solar Cells Beat the Near-Equilibrium Thermodynamic Limit?2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 28, p. 6514-6519Article in journal (Refereed)
    Abstract [en]

    Despite an impressive increase over the past decade, experimentally determined power conversion efficiencies of organic photovoltaic cells still fall considerably below the theoretical upper bound for near-equilibrium solar cells. Even in otherwise optimized devices, a prominent yet incompletely understood loss channel is the thermalization of photogenerated charge carriers in the density of states that is broadened by energetic disorder. Here, we demonstrate by extensive numerical modeling how this loss channel can be mitigated in carefully designed morphologies. Specifically, we show how funnel-shaped donor-and acceptor-rich domains in the phase-separated morphology that are characteristic of organic bulk heterojunction solar cells can promote directed transport of positive and negative charge carriers toward the anode and cathode, respectively. We demonstrate that in optimized funnel morphologies this kinetic, nonequilibrium effect, which is boosted by the slow thermalization of photogenerated charges, allows one to surpass the near-equilibrium limit for the same material in the absence of gradients.

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  • 30.
    Upreti, Tanvi
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Wilken, Sebastian
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Abo Akad Univ, Finland.
    Zhang, Huotian
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Slow Relaxation of Photogenerated Charge Carriers Boosts Open-Circuit Voltage of Organic Solar Cells2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 40, p. 9874-9881Article in journal (Refereed)
    Abstract [en]

    Among the parameters determining the efficiency of an organic solar cell, the open-circuit voltage (V-OC) is the one with most room for improvement. Existing models for the description of V-OC assume that photogenerated charge carriers are thermalized. Here, we demonstrate that quasi-equilibrium concepts cannot fully describe V-OC of disordered organic devices. For two representative donor:acceptor blends, it is shown that V-OC is actually 0.1-0.2 V higher than it would be if the system was in thermodynamic equilibrium. Extensive numerical modeling reveals that the excess energy is mainly due to incomplete relaxation in the disorder-broadened density of states. These findings indicate that organic solar cells work as nonequilibrium devices, in which part of the photon excess energy is harvested in the form of an enhanced V-OC.

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  • 31.
    van Reenen, Stephan
    et al.
    University of Oxford, England.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Snaith, Henry J.
    University of Oxford, England.
    Modeling Anomalous Hysteresis in Perovskite Solar Cells2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 19, p. 3808-3814Article in journal (Refereed)
    Abstract [en]

    Organic inorganic lead halide perovskites are distinct from most other semiconductors because they exhibit characteristics of both electronic and ionic motion. Accurate understanding of the optoelectronic impact of such properties is important to fully optimize devices and be aware of any limitations of perovskite solar cells and broader optoelectronic devices. Here we use a numerical drift-diffusion model to describe device operation of perovskite solar cells. To achieve hysteresis in the modeled current voltage characteristics, we must include both ion migration and electronic charge traps, serving as recombination centers. Trapped electronic charges recombine with oppositely charged free electronic carriers, of which the density depends on the bias-dependent ion distribution in the perovskite. Our results therefore show that reduction of either the density of mobile ionic species or carrier trapping at the perovskite interface will remove the adverse hysteresis in perovskite solar cells. This gives a clear target for ongoing research effort and unifies previously conflicting experimental observations and theories.

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  • 32.
    Wang, Jianqiu
    et al.
    Beihang Univ, Peoples R China; Natl Ctr Nanosci and Technol, Peoples R China.
    Xu, Jianqiu
    Nanjing Univ, Peoples R China.
    Yao, Nannan
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhang, Dongyang
    Beihang Univ, Peoples R China.
    Zheng, Zhong
    Natl Ctr Nanosci and Technol, Peoples R China.
    Xie, Shenkun
    Beihang Univ, Peoples R China; Natl Ctr Nanosci and Technol, Peoples R China.
    Zhang, Xuning
    Beihang Univ, Peoples R China.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhou, Huiqiong
    Natl Ctr Nanosci and Technol, Peoples R China.
    Zhang, Chunfeng
    Nanjing Univ, Peoples R China.
    Zhang, Yuan
    Beihang Univ, Peoples R China.
    A Comparative Study on Hole Transfer Inversely Correlated with Driving Force in Two Non-Fullerene Organic Solar Cells2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 14, p. 4110-4116Article in journal (Refereed)
    Abstract [en]

    We report a faster rate of hole transfer under a smaller AHomo in a comparative study of two group organic solar cells (OSCs) consisting of IT-4F as an acceptor and PBDBT and PBDBT-SF as donors. In the OSCs based on PBDBT. SF:IT-4F, a higher short-circuit current (J(SC)) was observed with a Delta(Homo) of 0.31 eV compared to a lower Jsc in PBDBT:IT-4F OSCs with a larger Delta(Homo) (0.45 eV). Intensive investigation indicates that the rate of transfer of a hole from IT-4F to PBDBT-SF or PBDBT is inversely proportional to the Delta(Homo) between IT-4F and donors. The larger Jsc in the PBDBT-SF:IT-4F device is attributed to a synergy of faster hole transfer, slower recombination, and rapid charge extraction enabled by desired morphology and balanced charge carrier mobilities with PBDBT-SF, suggesting that under a sufficiently high Delta(Homo), comprehensive considerations of the transport, film morphology, and energy levels are needed when designing new materials for high-performance OSCs.

  • 33.
    Wang, Xian
    et al.
    Beijing Normal Univ, Peoples R China.
    Huo, Dayujia
    Beijing Normal Univ, Peoples R China.
    Wang, Xin
    Beijing Normal Univ, Peoples R China.
    Li, Minjie
    Beijing Normal Univ, Peoples R China.
    Wang, Yong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wan, Yan
    Beijing Normal Univ, Peoples R China.
    Hot Carrier Dynamics and Charge Trapping in Surface Passivated beta-CsPbI3 Inorganic Perovskite2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 29, p. 6907-6913Article in journal (Refereed)
    Abstract [en]

    Thermodynamically stable CsPbI3 inorganic perovskite has achieved high efficiency exceeding 20% with surface defect passivation, but a thorough understanding on the photophysics properties of surface passivated CsPbI3 inorganic perovskite is still lacking. Herein, we have used transient absorption spectroscopy to investigate the photophysical properties of beta-CsPbI3 perovskites with and without passivation. The results indicate that the carrier trapping process has become slower because of the reduced deep defects that were varied to shallow defects due to surface passivation. The bimolecular recombination of beta-CsPbI3 was also accelerated because of the improved carrier mobility after healing surface defects by passivation agents. Moreover, the efficient defect passivation can also elongate the hot carrier lifetime from 0.26 to 0.37 ps by impeding the charge trapping process. Our findings reveal that the defects passivation is beneficial to enhance defect tolerance, improve carrier transport, and slow down the hot carrier cooling for developing high-performance photovoltaics.

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  • 34.
    Weng, Taoyu
    et al.
    State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China.
    Zou, Qi
    Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China.
    Zhang, Man
    State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China.
    Wu, Bin
    State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China.
    Baryshnikov, Glib V.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Shen, Shen
    State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China.
    Chen, Xuanying
    Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China.
    Ågren, Hans
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden; Henan Center for Outstanding Overseas Scientists, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, China.
    Jia, Xiaoyong
    Henan Center for Outstanding Overseas Scientists, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, China.
    Zhu, Liangliang
    State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200438, China.
    Enhancing the Operability of Photoexcitation-Controlled Aggregation-Induced Emissive Molecules in the Organic Phase2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, The Journal of Physical Chemistry Letters, Vol. 12, no 26, p. 6182-6189Article in journal (Refereed)
    Abstract [en]

    Controllable aggregation-induced emission luminogens (AIEgens) by photoexcitation can be conducted within a single solvent, thus opening new opportunities for preparing and processing smart materials. However, undesired side-reactions like photooxidation that can easily occur in the organic phase remain, limiting their applications. To enhance the operability of photoexcitation-controlled AIEgens (to specifically produce a phosphorescence characteristic) in the organic phase, in this work, we employ a typical prototype, hexathiobenzene, usually as the specific phosphorescent group, and investigate a series of physical and chemical factors, such as light intensity, dissolved oxygen content, and solvent polarity, to explore ways to control the photoexcitation-controllable AIEgens against the impurities from side-reactions. An organogel strategy was also developed to minimize interference factors and improve the practical application ability. We believe that the presented results provide new insights into the further development of the photoexcitation-based functional materials and the promotion of their practical usage.

  • 35.
    Xu, Yan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Shenzhen Univ, Peoples R China.
    Xu, Weidong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Hu, Zhang-Jun
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Steele, Julian A.
    Katholieke Univ Leuven, Belgium.
    Wang, Yang
    Nanjing Univ Posts & Telecommun, Peoples R China.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zheng, Guanhaojie
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Li, Xiangchun
    Nanjing Univ Posts & Telecommun, Peoples R China.
    Wang, Heyong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Xin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Solano, Eduardo
    ALBA Synchrotron Light Source, Spain.
    Roeffaers, Maarten B. J.
    Katholieke Univ Leuven, Belgium.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Qing, Jian
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Jinan Univ, Peoples R China.
    Zhang, Wenjing
    Shenzhen Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Impact of Amine Additives on Perovskite Precursor Aging: A Case Study of Light-Emitting Diodes2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 25, p. 5836-5843Article in journal (Refereed)
    Abstract [en]

    Amines are widely employed as additives for improving the performance of metal halide perovskite optoelectronic devices. However, amines are well-known for their high chemical reactivity, the impact of which has yet to receive enough attention from the perovskite light-emitting diode community. Here, by investigating an unusual positive aging effect of CH3NH3I/CsI/PbI2 precursor solutions as an example, we reveal that amines gradually undergo N-formylation in perovskite precursors over time. This reaction is initialized by hydrolysis of dimethylformamide in the acidic chemical environment. Further investigations suggest that the reaction products collectively impact perovskite crystallization and eventually lead to significantly enhanced external quantum efficiency values, increasing from similar to 2% for fresh solutions to greater than or similar to 12% for aged ones. While this case study provides a positive aging effect, a negative aging effect is possible in other perovksite systems. Our findings pave the way for more reliable and reproducible device fabrication and call for further attention to underlying chemical reactions within the perovskite inks once amine additives are included.

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  • 36.
    Yang, Jinpeng
    et al.
    Yangzhou Univ, Peoples R China; Inst Mol Sci, Japan.
    Sato, Haruki
    Chiba Univ, Japan.
    Orio, Hibiki
    Chiba Univ, Japan.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ueno, Nobuo
    Chiba Univ, Japan.
    Yoshida, Hiroyuki
    Chiba Univ, Japan; Chiba Univ, Japan.
    Yamada, Takashi
    Osaka Univ, Japan.
    Kera, Satoshi
    Inst Mol Sci, Japan.
    Accessing the Conduction Band Dispersion in CH3NH3PbI3 Single Crystals2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 15, p. 3773-3778Article in journal (Refereed)
    Abstract [en]

    The conduction band dispersion in methylammonium lead iodide (CH3NH3PbI3) was studied by both angle-resolved two-photon photoelectron spectroscopy (AR-2PPE) with low photon intensity (similar to 0.0125 nJ/pulse) and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy dispersion of the conduction band along the Gamma-M direction was first observed by these independent methods under different temperatures, and the dispersion was found to be consistent with band calculation under the cubic phase. The effective mass of the electrons at the Gamma point was estimated to be (0.20 +/- 0.05)m(0) at the temperature of 90 K. The observed conduction band energy was different between the AR-LEIPS and AR-2PPE, which was ascribed to the electronic-correlation-dependent difference of initial and final states probing processes. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.

  • 37.
    Yao, Nannan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Jianqiu
    Beihang Univ, Peoples R China.
    Chen, Zeng
    Zhejiang Univ, Peoples R China.
    Bian, Bian
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Xia, Yuxin
    Hasselt Univ, Belgium.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Jianqi
    Natl Ctr Nanosci & Technol, Peoples R China.
    Qin, Leiqiang
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhu, Haiming
    Zhejiang Univ, Peoples R China.
    Zhang, Yuan
    Beihang Univ, Peoples R China.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Efficient Charge Transport Enables High Efficiency in Dilute Donor Organic Solar Cells2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 20, p. 5039-5044Article in journal (Refereed)
    Abstract [en]

    The donor/acceptor weight ratio is crucial for photovoltaic performance of organic solar cells (OSCs). Here, we systematically investigate the photovoltaic behaviors of PM6:Y6 solar cells with different stoichiometries. It is found that the photovoltaic performance is tolerant to PM6 contents ranging from 10 to 60 wt %. Especially an impressive efficiency over 10% has been achieved in dilute donor solar cells with 10 wt % PM6 enabled by efficient charge generation, electron/ hole transport, slow charge recombination, and field-insensitive extraction. This raises the question about the origin of efficient hole transport in such dilute donor structure. By investigating hole mobilities of PM6 diluted in Y6 and insulators, we find that effective hole transport pathway is mainly through PM6 phase in PM6:Y6 blends despite with low PM6 content. The results indicate that a low fraction of polymer donors combines with near-infrared nonfullerene acceptors could achieve high photovoltaic performance, which might be a candidate for semitransparent windows.

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  • 38.
    Yu, Hongling
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Heyong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Tiankai
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Yi, Chang
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Zheng, Guanhaojie
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yin, Chunyang
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Karlsson, Max
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Qin, Jiajun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Jianpu
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Liu, Xiaoke
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Color-Stable Blue Light-Emitting Diodes Enabled by Effective Passivation of Mixed Halide Perovskites2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 26, p. 6041-6047Article in journal (Refereed)
    Abstract [en]

    Bandgap tuning through mixing halide anions is one of the most attractive features for metal halide perovskites. However, mixed halide perovskites usually suffer from phase segregation under electrical biases. Herein, we obtain high-performance and color-stable blue perovskite LEDs (PeLEDs) based on mixed bromide/ chloride three-dimensional (3D) structures. We demonstrate that the color instability of CsPb(Br1-xClx)(3) PeLEDs results from surface defects at perovskite grain boundaries. By effective defect passivation, we achieve color-stable blue electroluminescence from CsPb(Br1-xClx)(3) PeLEDs, with maximum external quantum efficiencies of up to 4.5% and high luminance of up to 5351 cd m(-2) in the sky-blue region (489 nm). Our work provides new insights into the color instability issue of mixed halide perovskites and can spur new development of high-performance and color-stable blue PeLEDs.

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  • 39.
    Zhang, Jibin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Jinan Univ, Peoples R China; Huazhong Univ Sci & Technol, Peoples R China.
    Yin, Chunyang
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Yang, Fei
    Huazhong Univ Sci & Technol, Peoples R China.
    Yao, Yuan
    Huazhong Univ Sci & Technol, Peoples R China; Huazhong Inst Electroopt, Peoples R China.
    Yuan, Fanglong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chen, Hongting
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Jinan Univ, Peoples R China; Huazhong Univ Sci & Technol, Peoples R China.
    Wang, Rongwen
    Huazhong Univ Sci & Technol, Peoples R China.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Zhejiang Univ, Peoples R China.
    Tu, Guoli
    Huazhong Univ Sci & Technol, Peoples R China.
    Hou, Lintao
    Jinan Univ, Peoples R China.
    Highly Luminescent and Stable CsPbI3 Perovskite Nanocrystals with Sodium Dodecyl Sulfate Ligand Passivation for Red-Light-Emitting Diodes2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 9, p. 2437-2443Article in journal (Refereed)
    Abstract [en]

    CsPbI3 perovskite nanocrystals (NCs) have recently emerged as promising materials for optoelectronic devices because of their superior properties. However, the poor stability of the CsPbI3 NCs induced by easy ligand desorption represents a key issue limiting their practical applications. Herein, we report stable and highly luminescent black-phase CsPbI3 NCs passivated by novel ligands of sodium dodecyl sulfate (SDS). Theoretical calculation results reveal a stronger adsorption energy of SDS molecules at the CsPbI3 surface than that of commonly used oleic acid. As a result, the defect formation caused by the ligand loss during the purification process is greatly suppressed. The optimized SDS- CsPbI3 NCs exhibit significantly reduced surface defects, much enhanced stability, and superior photoluminescence efficiency. The red perovskite light-emitting diodes based on the SDS-CsPbI3 NCs demonstrate an external quantum efficiency of 8.4%, which shows a 4-fold improvement compared to the devices based on the oleic acid-modified CsPbI3 NCs.

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  • 40.
    Zhang, Liangdong
    et al.
    Nanjing Tech Univ, Peoples R China.
    Jiang, Tao
    Nanjing Tech Univ, Peoples R China.
    Yi, Chang
    Nanjing Tech Univ, Peoples R China.
    Wu, Jiquan
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Liu, Xiaoke
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    He, Yaron
    Nanjing Tech Univ, Peoples R China.
    Miao, Yanfeng
    Nanjing Tech Univ, Peoples R China.
    Zhang, Ya
    Nanjing Tech Univ, Peoples R China.
    Zhang, Huotian
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Xie, Xinrui
    Zhejiang Univ, Peoples R China.
    Wang, Peng
    Zhejiang Univ, Peoples R China.
    Li, Renzhi
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Huang, Wei
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China; NPU, Peoples R China.
    Wang, Jianpu
    Nanjing Tech Univ, Peoples R China.
    Bright Free Exciton Electroluminescence from Mn-Doped Two-Dimensional Layered Perovskites2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 11, p. 3171-3175Article in journal (Refereed)
    Abstract [en]

    Two-dimensional (2D) perovskites incorporating hydrophobic organic spacer cations show improved film stability and morphology compared to their three-dimensional (3D) counterparts. However, 2D perovskites usually exhibit low photoluminescence quantum efficiency (PLQE) owing to strong exciton-phonon interaction at room temperature, which limits their efficiency in light-emitting diodes (LEDs). Here, we demonstrate that the device performance of 2D perovskite LEDs can be significantly enhanced by doping Mn(2+)in (benzimidazolium)(2)PbI4 2D perovskite films to suppress the exciton-phonon interaction. The distorted [PbI6](4-) octahedra by Mn-doping and the rigid benzimidazolium (BIZ) ring without branched chains in the 2D perovskite structure lead to improved crystallinity and rigidity of the perovskites, resulting in suppressed phonon-exciton interaction and enhanced PLQE. On the basis of this strategy, for the first time, we report yellow electroluminescence from free excitons in 2D (n = 1) perovskites with a maximum brightness of 225 cd m(-2) and a peak EQE of 0.045%.

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  • 41.
    Zhao, Ningjiu
    et al.
    Songshan Lake Mat Lab, Peoples R China.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zou, Xianshao
    Lund Univ, Sweden.
    Su, Xiaojun
    Guangzhou Maritime Univ, Peoples R China.
    Dang, Fan
    Songshan Lake Mat Lab, Peoples R China.
    Wen, Guanzhao
    Guangzhou Univ, Peoples R China.
    Zhang, Wei
    Guangzhou Univ, Peoples R China.
    Zheng, Kaibo
    Lund Univ, Sweden.
    Chen, Hailong
    Songshan Lake Mat Lab, Peoples R China.
    Wu, Kehui
    Songshan Lake Mat Lab, Peoples R China.
    Photoinduced Polaron Formation in a Polymerized Electron-Acceptor Semiconductor2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 23, p. 5143-5150Article in journal (Refereed)
    Abstract [en]

    Polymerized small molecular acceptor (PSMA) based all-polymer solar cells (all-PSC) have achieved power conversion efficiencies (PCE) over 16%, and the PSMA is considered to hold great promise for further improving the performance of all-PSC. Yet, in comparison with that of the polymer donor, the photophysics of a polymerized acceptor remains poorly understood. Herein, the excited state dynamics in a polymerized acceptor PZT810 was comprehensively investigated under various pump intensities and photon energies. The excess excitation energy was found to play a key role in excitons dissociation into free polarons for neat PSMA films, while free polarons cannot be generated from the polaron pairs in neat acceptor films. This work reveals an in-depth understanding of relaxation dynamics for PSMAs and that the underlying photophysical origin of PSMA can be mediated by excitation energies and intensities. These results would benefit the realization of the working mechanism for all-PSC and the designing of new PSMAs.

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