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Braun, Slawomir
Alternative names
Publications (10 of 50) Show all publications
Wang, C., Ni, S., Braun, S., Fahlman, M. & Liu, X. (2019). Effects of water vapor and oxygen on non-fullerene small molecule acceptors. Journal of Materials Chemistry C, 7(4), 879-886
Open this publication in new window or tab >>Effects of water vapor and oxygen on non-fullerene small molecule acceptors
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2019 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 7, no 4, p. 879-886Article in journal (Refereed) Published
Abstract [en]

Due to the rapid development of non-fullerene acceptors (NFAs), the efficiency of organic solar cells is steadily being improved. The stability of organic solar cells also is expected to be enhanced with the introduction of the NFAs, yet the stability of NFAs themselves have been less investigated to date. In this paper, the stability of a set of typical NFAs was studied in situ employing photoelectron spectroscopy. The studied molecules show higher resistance to water vapor and thermal stress compared to fullerenes. For water vapor exposure, the highest occupied molecular orbital (HOMO) of NFAs undergoes only minor and reversible changes and the NFAs/substrate work function stays constant. Exposure to oxygen gas significantly modified the electronic structure of the NFAs and the effect was only partially reversible by annealing. However, the presence of water vapor was shown to slow down the degradation caused by oxygen. This is in stark contrast to fullerenes that undergo irreversible degradation upon water vapor exposure.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Condensed Matter Physics Nano Technology
Identifiers
urn:nbn:se:liu:diva-154288 (URN)10.1039/C8TC05475D (DOI)000459571400007 ()2-s2.0-85060595857 (Scopus ID)
Note

Funding agencies: Knut and Alice Wallenberg Foundation project "Tail of the Sun; Swedish Research Council [2016-05498]; Swedish Foundation for Strategic Research [SE13-0060]; Ministry of Science and Technology [2016YFA0200700]; NSFC [21504066, 21534003]; Swedish Energy Age

Available from: 2019-02-01 Created: 2019-02-01 Last updated: 2019-03-20Bibliographically approved
Yang, J., Xiong, S., Qu, T., Zhang, Y., He, X., Guo, X., . . . Bao, Q. (2019). Extremely Low-Cost and Green Cellulose Passivating Perovskites for Stable and High-Performance Solar Cells. ACS Applied Materials and Interfaces, 11(14), 13491-13498
Open this publication in new window or tab >>Extremely Low-Cost and Green Cellulose Passivating Perovskites for Stable and High-Performance Solar Cells
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2019 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 14, p. 13491-13498Article in journal (Refereed) Published
Abstract [en]

The fast evolution of metal halide perovskite solar cells has opened a new chapter in the field of renewable energy. High-quality perovskite films as the active layers are essential for both high efficiency and long-term stability. Here, the perovskite films with enlarged crystal grain size and decreased defect density are fabricated by introducing the extremely low-cost and green polymer, ethyl cellulose (EC), into the perovskite layer. The addition of EC triggers hydrogen bonding interactions between EC and the perovskite, passivating the charge defect traps at the grain boundaries. The long chain of EC further acts as a scaffold for the perovskite structure, eliminating the annealing-induced lattice strain during the film fabrication process. The resulting devices with the EC additive exhibit a remarkably enhanced average power conversion efficiency from 17.11 to 19.27% and an improvement of all device parameters. The hysteresis index is found to decrease by three times from 0.081 to 0.027, which is attributed to suppressed ion migration and surface charge trapping. In addition, the defect passivation by EC significantly improves the environmental stability of the perovskite films, yielding devices that retain 80% of their initial efficiency after 30 days in ambient air at 45% relative humidity, whereas the pristine devices without EC fully degrade. This work provides a low-cost and green avenue for passivating defects that improves both the efficiency and operational stability of perovskite solar cells.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
cellulose; passivation; perovskite solar cells; efficiency; stability
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-157220 (URN)10.1021/acsami.9b01740 (DOI)000464769400049 ()30880387 (PubMedID)2-s2.0-85064109044 (Scopus ID)
Note

Funding Agencies|National Science Foundation of China [11604099, 21875067, 51873138, 51811530011]; Shanghai Science and Technology Innovation Action Plan [19QA1403100, 17JC1402500]; National Key Project for Basic Research of China [2017YFA0303403]; Swedish Research Council [2016-05498]; STINT grant [CH2017-7163]

Available from: 2019-06-13 Created: 2019-06-13 Last updated: 2019-06-18Bibliographically approved
Wang, C., Ouyang, L., Xu, X., Braun, S., Liu, X. & Fahlman, M. (2018). Relationship of Ionization Potential and Oxidation Potential of Organic Semiconductor Films Used in Photovoltaics. Solar RRL, 2(9)
Open this publication in new window or tab >>Relationship of Ionization Potential and Oxidation Potential of Organic Semiconductor Films Used in Photovoltaics
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2018 (English)In: Solar RRL, ISSN 2367-198X, Vol. 2, no 9Article in journal (Refereed) Published
Abstract [en]

Ultraviolet photoelectron spectroscopy (UPS) and cyclic voltammetry (CV) are employed to measure energy levels for charge transport in organic semiconductor films. A series of classical molecules/polymers used in organic bulk heterojunction solar cells are deposited on platinum substrates/electrodes to form thin films and a linear relationship of vertical ionization potential (IP) measured by UPS and relative oxidation potential (Eox) obtained by CV is found, with a slope equal to unity. The intercept varies with the different reference redox couples and repeated potential sweep numbers during experiment processes. The relationship provides for an easy conversion of values obtained by the two techniques and correlates well with device parameters. The precision in the CV-derived IP values is not sufficient, however, to enable precise design of energy level alignment at heterojunction and the approach does not improve upon the current ?best practice? for obtaining donor ionization potential?acceptor electron affinity gaps at heterojunctions.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2018
Keywords
cyclic voltammetry, ionization potential, linear relationship, organic photovoltaics, oxidation potential, semiconductor films, UV photoelectron spectroscopy
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-151711 (URN)10.1002/solr.201800122 (DOI)000443972900011 ()
Funder
Swedish Foundation for Strategic Research , SE13‐0060Knut and Alice Wallenberg FoundationSwedish Research Council, 2016‐05498Linköpings universitet, 2009 00971Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-10-10Bibliographically approved
Bao, Q., Liu, X., Braun, S., Yanqing, L., Jianxin, T., Chungang, D. & Fahlman, M. (2017). Intermixing Effect on Electronic Structures of TQ1:PC71BM Bulk Heterojunction in Organic Photovoltaics. Solar RRL, 1(10), Article ID 1700142.
Open this publication in new window or tab >>Intermixing Effect on Electronic Structures of TQ1:PC71BM Bulk Heterojunction in Organic Photovoltaics
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2017 (English)In: Solar RRL, ISSN 2367-198X, Vol. 1, no 10, article id 1700142Article in journal (Refereed) Published
Abstract [en]

The interface energetics and intermixing effects of the donor/acceptor bulk heterojunction (BHJ) blends of poly[2,3‐bis‐(3‐octyloxyphenyl) quinoxaline‐5, 8‐dilyl‐alt‐thiophene‐2, 5‐diyl]: [6,6]‐phenyl C71butyric acid methyl ester (TQ1:PC71BM) have been investigated using ultraviolet photoemission spectroscopy (UPS) in combination with the integer charge transfer model. The TQ1:PC71BM represents the useful model system for BHJ organic photovoltaics featuring effective charge generation and transport. It finds out that the positive integer charge state of TQ1 are equal in energy to the negative integer charge state of PC71BM, leading to a negligible potential step at TQ1:PC71BM interface and thus the vacuum level alignment. It is observed that the TQ1 accumulates on the top of TQ1:PC71BM BHJ and UPS spectra as function of various blend ratios suggest that the TQ1 mixes finely with PC71BM with the little work function modification in a wide range. In addition, no significant influence of the long‐range Coulomb interactions or the intermolecular hybridization on the occupied electronic structures is present for the well‐intermixed TQ1:PC71BM BHJs. These findings provide deep insights into the properties of BHJ blends and are beneficial for the performance optimization in organic photovoltaics.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-150513 (URN)10.1002/solr.201700142 (DOI)
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2019-01-09Bibliographically approved
Bao, Q., Fabiano, S., Andersson, M., Braun, S., Sun, Z., Crispin, X., . . . Fahlman, M. (2016). Energy Level Bending in Ultrathin Polymer Layers Obtained through Langmuir-Shafer Deposition. Advanced Functional Materials, 26(7), 1077-1084
Open this publication in new window or tab >>Energy Level Bending in Ultrathin Polymer Layers Obtained through Langmuir-Shafer Deposition
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2016 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 7, p. 1077-1084Article in journal (Refereed) Published
Abstract [en]

The semiconductor-electrode interface impacts the function and the performance of (opto) electronic devices. For printed organic electronics the electrode surface is not atomically clean leading to weakly interacting interfaces. As a result, solution-processed organic ultrathin films on electrodes typically form islands due to dewetting. It has therefore been utterly difficult to achieve homogenous ultrathin conjugated polymer films. This has made the investigation of the correct energetics of the conjugated polymer-electrode interface impossible. Also, this has hampered the development of devices including ultrathin conjugated polymer layers. Here, LangmuirShafer-manufactured homogenous mono-and multilayers of semiconducting polymers on metal electrodes are reported and the energy level bending using photoelectron spectroscopy is tracked. The amorphous films display an abrupt energy level bending that does not extend beyond the first monolayer. These findings provide new insights of the energetics of the polymer-electrode interface and opens up for new high-performing devices based on ultrathin semiconducting polymers.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2016
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering Biological Sciences
Identifiers
urn:nbn:se:liu:diva-126253 (URN)10.1002/adfm.201504729 (DOI)000371079300010 ()
Note

Funding Agencies|EU project SUNFLOWER of FP7 cooperation programme [287594]; Swedish Research Council [2013-4022]; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Swedish Research Council Linnaeus grant LiLi-NFM; Advanced Functional Materials Center at Linkoping University

Available from: 2016-03-21 Created: 2016-03-21 Last updated: 2017-11-30
del Pozo, F. G., Fabiano, S., Pfattner, R., Georgakopoulos, S., Galindo, S., Liu, X., . . . Mas-Torrent, M. (2016). Single Crystal-Like Performance in Solution-Coated Thin-Film Organic Field-Effect Transistors. Advanced Functional Materials, 26(14), 2379-2386
Open this publication in new window or tab >>Single Crystal-Like Performance in Solution-Coated Thin-Film Organic Field-Effect Transistors
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2016 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 14, p. 2379-2386Article in journal (Refereed) Published
Abstract [en]

In electronics, the field-effect transistor (FET) is a crucial cornerstone and successful integration of this semiconductor device into circuit applications requires stable and ideal electrical characteristics over a wide range of temperatures and environments. Solution processing, using printing or coating techniques, has been explored to manufacture organic field-effect transistors (OFET) on flexible carriers, enabling radically novel electronics applications. Ideal electrical characteristics, in organic materials, are typically only found in single crystals. Tiresome growth and manipulation of these hamper practical production of flexible OFETs circuits. To date, neither devices nor any circuits, based on solution-processed OFETs, has exhibited an ideal set of characteristics similar or better than todays FET technology based on amorphous silicon. Here, bar-assisted meniscus shearing of dibenzo-tetrathiafulvalene to coat-process self-organized crystalline organic semiconducting domains with high reproducibility is reported. Including these coatings as the channel in OFETs, electric field and temperature-independent charge carrier mobility and no bias stress effects are observed. Furthermore, record-high gain in OFET inverters and exceptional operational stability in both air and water are measured.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2016
Keywords
Organic field-effect transistors, thin-film coating, charge carrier mobility
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Physical Sciences
Identifiers
urn:nbn:se:liu:diva-127774 (URN)10.1002/adfm.201502274 (DOI)000374258100014 ()
Note

Funding Agencies|ERC [StG 2012-306826]; Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN); DGI (Spain) [BE-WELL CTQ2013-40480-R]; Generalitat de Catalunya [2014-SGR-17]; Advanced Functional Materials Center at Linkoping University; Onnesjo Foundation; Knut and Alice Wallenberg Foundation; Swedish Foundation for Strategic Research (SSF); Universidad Tecnica de Ambato; Secretaria de Educacion Superior, Ciencia, Tecnologia e Innovacion

Available from: 2016-05-12 Created: 2016-05-12 Last updated: 2017-11-30
Bao, Q., Liu, X., Braun, S., Gao, F. & Fahlman, M. (2015). Energetics at Doped Conjugated Polymer/Electrode Interfaces. ADVANCED MATERIALS INTERFACES, 2(2)
Open this publication in new window or tab >>Energetics at Doped Conjugated Polymer/Electrode Interfaces
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2015 (English)In: ADVANCED MATERIALS INTERFACES, ISSN 2196-7350, Vol. 2, no 2Article in journal (Refereed) Published
Abstract [en]

n/a

Place, publisher, year, edition, pages
Wiley: 12 months, 2015
National Category
Physical Sciences Biological Sciences
Identifiers
urn:nbn:se:liu:diva-114420 (URN)10.1002/admi.201400403 (DOI)000348287700008 ()
Note

Funding Agencies|EU [287594]; Swedish Research Council Linnaeus grant LiLi-NFM; Swedish Research Council [2013-4022]; Goran Gustafsson Foundation for Research in Natural Sciences and Medicine; Advanced Functional Materials Center at Linkoping University

Available from: 2015-03-02 Created: 2015-02-20 Last updated: 2015-06-05
Bao, Q., Liu, X., Wang, E., Fang, J., Gao, F., Braun, S. & Fahlman, M. (2015). Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules. Advanced Materials Interfaces, 2(12), 1-6, Article ID 1500204.
Open this publication in new window or tab >>Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules
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2015 (English)In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 2, no 12, p. 1-6, article id 1500204Article in journal (Refereed) Published
Abstract [en]

Regular energetics at a conjugated electrolyte/electrode modifier are found and controlled by equilibration of the Fermi level and an additional interface double dipole step induced by ionic functionality. Based on the results, design rules for conjugated electrolyte/electrode modifiers to achieve the smallest charge injection/exaction barrier and break through the current thickness limitation are proposed.

Place, publisher, year, edition, pages
John Wiley & Sons, 2015
Keywords
Conjugated electrolyte, electrode modifier, energetics, organic electronics
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-118917 (URN)10.1002/admi.201500204 (DOI)000360057500011 ()
Note

On the day of the defence date the status of this article was Manuscript.

Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2017-03-16Bibliographically approved
Lindell, L., Vahlberg, C., Uvdal, K., Fahlman, M. & Braun, S. (2015). Self-assembled monolayer engineered interfaces: Energy level alignment tuning through chain length and end-group polarity. Journal of Electron Spectroscopy and Related Phenomena, 204, 140-144
Open this publication in new window or tab >>Self-assembled monolayer engineered interfaces: Energy level alignment tuning through chain length and end-group polarity
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2015 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 204, p. 140-144Article in journal (Refereed) Published
Abstract [en]

We explore the different mechanisms through which self-assembled monolayers can tailor energy level alignment at metal-organic semiconductor interfaces. We show that the large work function variation that can be induced by the self-assembled monolayer on gold has limited ability to tailor the interface energy level alignment of a subsequent organic semiconductor overlayer. (C) 2015 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2015
Keywords
Self-assembled monolayer; SAM; F4-TCNQ; Interfaces; Energy level alignment
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-122663 (URN)10.1016/j.elspec.2015.04.006 (DOI)000363078400017 ()
Note

Funding Agencies|Swedish Energy Agency, STEM; Swedish Research Council [2013-4022]; Goran Gustafsson Foundation

Available from: 2015-11-16 Created: 2015-11-13 Last updated: 2017-12-01
Bubnova, O., Khan, Z. U., Wang, H., Braun, S., Evans, D. R., Fabretto, M., . . . Crispin, X. (2014). Corrigendum: Semi-metallic polymers. Nature Materials, 13, 662-662
Open this publication in new window or tab >>Corrigendum: Semi-metallic polymers
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2014 (English)In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 13, p. 662-662Article in journal (Refereed) Published
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-113955 (URN)10.1038/nmat3981 (DOI)
Available from: 2015-02-04 Created: 2015-02-04 Last updated: 2018-08-20
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