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Zuo, G., Liu, X., Fahlman, M. & Kemerink, M. (2018). High Seebeck Coefficient in Mixtures of Conjugated Polymers. Paper presented at 2018/05/14. Advanced Functional Materials, 28(15), Article ID 1703280.
Open this publication in new window or tab >>High Seebeck Coefficient in Mixtures of Conjugated Polymers
2018 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 15, article id 1703280Article in journal (Refereed) Published
Abstract [en]

A universal method to obtain record?high electronic Seebeck coefficients is demonstrated while preserving reasonable conductivities in doped blends of organic semiconductors through rational design of the density of states (DOSs). A polymer semiconductor with a shallow highest occupied molecular orbital (HOMO) level?poly(3?hexylthiophene) (P3HT) is mixed with materials with a deeper HOMO (PTB7, TQ1) to form binary blends of the type P3HTx:B1?x (0 ≤ x ≤ 1) that is p?type doped by F4TCNQ. For B = PTB7, a Seebeck coefficient S = 1100 µV K?1 with conductivity σ = 0.3 S m?1 at x = 0.10 is achieved, while for B = TQ1, S = 2000 µV K?1 and σ = 0.03 S m?1 at x = 0.05 is found. Kinetic Monte Carlo simulations with parameters based on experiments show good agreement with the experimental results, confirming the intended mechanism. The simulations are used to derive a design rule for parameter tuning. These results can become relevant for low?power, low?cost applications like (providing power to) autonomous sensors, in which a high Seebeck coefficient translates directly to a proportionally reduced number of legs in the thermogenerator, and hence in reduced fabrication cost and complexity.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2018
Keywords
conjugated polymers, doping, kinetic Monte Carlo simulations, organic thermoelectrics, Seebeck coefficients
National Category
Materials Engineering Physical Sciences
Identifiers
urn:nbn:se:liu:diva-147779 (URN)10.1002/adfm.201703280 (DOI)000430101100004 ()
Conference
2018/05/14
Note

Funding Agencies: Chinese Scholarship Council (CSC)

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-05-31Bibliographically 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)000417425000003 ()
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2018-09-06Bibliographically approved
Wang, C., Zhang, W., Meng, X., Bergqvist, J., Liu, X., Genene, Z., . . . Fahlman, M. (2017). Ternary Organic Solar Cells with Minimum Voltage Losses. Advanced Energy Materials, 7(21), Article ID 1700390.
Open this publication in new window or tab >>Ternary Organic Solar Cells with Minimum Voltage Losses
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2017 (English)In: Advanced Energy Materials, ISSN 1614-6840, Vol. 7, no 21, article id 1700390Article in journal (Refereed) Published
Abstract [en]

A new strategy for designing ternary solar cells is reported in this paper. A low-bandgap polymer named PTB7-Th and a high-bandgap polymer named PBDTTS-FTAZ sharing the same bulk ionization potential and interface positive integer charge transfer energy while featuring complementary absorption spectra are selected. They are used to fabricate efficient ternary solar cells, where the hole can be transported freely between the two donor polymers and collected by the electrode as in one broadband low bandgap polymer. Furthermore, the fullerene acceptor is chosen so that the energy of the positive integer charge transfer state of the two donor polymers is equal to the energy of negative integer charge transfer state of the fullerene, enabling enhanced dissociation of all polymer donor and fullerene acceptor excitons and suppressed bimolecular and trap assistant recombination. The two donor polymers feature good miscibility and energy transfer from high-bandgap polymer of PBDTTS-FTAZ to low-bandgap polymer of PTB7-Th, which contribute to enhanced performance of the ternary solar cell.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
binary equivalent, minimum voltage losses, same bulk and interface energy, ternary solar cells
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:liu:diva-143026 (URN)10.1002/aenm.201700390 (DOI)000414711100002 ()2-s2.0-85025441174 (Scopus ID)
Note

Funding agencies: Knut and Alice Wallenberg Foundation; Swedish Research Council [2016-05498]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]; Goran Gustafsson Foundat

Available from: 2017-11-15 Created: 2017-11-15 Last updated: 2017-12-05Bibliographically approved
Malti, A., Edberg, J., Granberg, H., Ullah Khan, Z., Andreasen, J. W., Liu, X., . . . Berggren, M. (2016). An Organic Mixed Ion–Electron Conductor for Power Electronics. Advanced Science, Article ID 1500305.
Open this publication in new window or tab >>An Organic Mixed Ion–Electron Conductor for Power Electronics
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2016 (English)In: Advanced Science, ISSN 2198-3844, article id 1500305Article in journal (Refereed) Published
Abstract [en]

A mixed ionic–electronic conductor based on nanofibrillated cellulose composited with poly(3,4-ethylene-dioxythio­phene):­poly(styrene-sulfonate) along with high boiling point solvents is demonstrated in bulky electrochemical devices. The high electronic and ionic conductivities of the resulting nanopaper are exploited in devices which exhibit record values for the charge storage capacitance (1F) in supercapacitors and transconductance (1S) in electrochemical transistors.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2016
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-123225 (URN)10.1002/advs.201500305 (DOI)000370336500011 ()
Note

Funding agencies:  Knut and Alice Wallenberg foundation [KAW 2011.0050]; Onnesjo Foundation; Advanced Functional Materials Center at Linkoping University; Stiftelsen for strategisk forskning (SSF); RISE Research Institutes of Sweden; U.S. National Science Foundation [DMR-12

Available from: 2015-12-08 Created: 2015-12-08 Last updated: 2018-02-15
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
Kesters, J., Govaerts, S., Pirotte, G., Drijkoningen, J., Chevrier, M., Van den Brande, N., . . . Maes, W. (2016). High-Permittivity Conjugated Polyelectrolyte Interlayers for High-Performance Bulk Heterojunction Organic Solar Cells. ACS Applied Materials and Interfaces, 8(10), 6309-6314
Open this publication in new window or tab >>High-Permittivity Conjugated Polyelectrolyte Interlayers for High-Performance Bulk Heterojunction Organic Solar Cells
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2016 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 10, p. 6309-6314Article in journal (Refereed) Published
Abstract [en]

Conjugated polyelectrolyte (CPE) interfacial layers present a powerful way to boost the I-V characteristics of organic photovoltaics. Nevertheless, clear guidelines with respect to the structure of high-performance interlayers are still lacking. In this work, impedance spectroscopy is applied to probe the dielectric permittivity of a series of polythiophene-based CPEs. The presence of ionic pendant groups grants the formation of a capacitive double layer, boosting the charge extraction and device efficiency. A counteracting effect is the diminishing affinity with the underlying photoactive layer. To balance these two effects, we found copolymer structures containing nonionic side chains to be beneficial.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
Keywords
organic photovoltaics; cathode interlayers; conjugated polyelectrolytes; impedance spectroscopy; dielectric permittivity
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-127270 (URN)10.1021/acsami.6b00242 (DOI)000372479300002 ()26927416 (PubMedID)
Note

Funding Agencies|IAP project Functional Supramolecular Systems [7/05]; Science Policy Office of the Belgian Federal Government (BELSPO); Research Program of the Research Foundation Flanders (FWO) [G.0415.14N]; Foundation for Fundamental Research on Matter (FOM) from The Netherlands Organization for Scientific Research (NWO) [V0714M-13MV60]; Swedish Research Council Linnaeus LiLi-NFM at Linkoping University; Vrije Universiteit Brussel (VUB); University of Montpellier; CNRS; University of Mons

Available from: 2016-04-20 Created: 2016-04-19 Last updated: 2017-11-01
Gaceur, M., Ben Dkhil, S., Duche, D., Bencheikh, F., Simon, J.-J., Escoubas, L., . . . Ackermann, J. (2016). Ligand-Free Synthesis of Aluminum-Doped Zinc Oxide Nanocrystals and their Use as Optical Spacers in Color-Tuned Highly Efficient Organic Solar Cells. Advanced Functional Materials, 26(2), 243-253
Open this publication in new window or tab >>Ligand-Free Synthesis of Aluminum-Doped Zinc Oxide Nanocrystals and their Use as Optical Spacers in Color-Tuned Highly Efficient Organic Solar Cells
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2016 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 2, p. 243-253Article in journal (Refereed) Published
Abstract [en]

The color of polymer solar cells using an opaque electrode is given by the reflected light, which depends on the composition and thickness of each layer of the device. Metal-oxide-based optical spacers are intensively studied in polymer solar cells aiming to optimize the light absorption. However, the low conductivity of materials such as ZnO and TiO2 limits the thickness of such optical spacers to tenths of nanometers. A novel synthesis route of cluster-free Al-doped ZnO (AZO) nanocrystals (NCs) is presented for solution processing of highly conductive layers without the need of temperature annealing, including thick optical spacers on top of polymer blends. The processing of 80 nm thick optical spacers based on AZO nanocrystal solutions on top of 200 nm thick polymer blend layer is demonstrated leading to improved photocurrent density of 17% compared to solar cells using standard active layers of 90 nm in combination with thin ZnO-based optical spacers. These AZO NCs also open new opportunities for the processing of high-efficiency color tuned solar cells. For the first time, it is shown that applying solution-processed thick optical spacer with polymer blends of different thicknesses can process solar cells of similar efficiency over 7% but of different colors.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2016
Keywords
azo; interfacial layers; nanocrystals; organic solar cells; zinc oxide
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124634 (URN)10.1002/adfm.201502929 (DOI)000368041200009 ()
Note

Funding Agencies|EU [FP7-ICT-2011-7, 287594]; SFUMATO-FUI Project [AAP12]; Generalitat Valenciana (Project Institute of Nanotechnologies for Clean Energies) [ISIC/2012/008]

Available from: 2016-02-09 Created: 2016-02-08 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
Malti, A., Brooke, R., Liu, X., Zhao, D., Andersson Ersman, P., Fahlman, M., . . . Crispin, X. (2015). A substrate-free electrochromic device.
Open this publication in new window or tab >>A substrate-free electrochromic device
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2015 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Electrochromic displays based on conducting polymers offer higher contrast, are cheaper, faster, more durable, and easier to synthesize as well as to process than their non-polymeric counterparts. The field of organic electrochromics has made considerable strides in the last decade with the development of new materials and methods. Here, we present a cellulose composite combining PEDOT:PSS and TiO2 that is a free-standing electrochromic material. Owing to the excellent refractive properties of TiO2, this nanocomposite is white in the neutral state and, when reduced, turns blue resulting in a color contrast exceeding 30. The composite has a granular morphology and, as shown by AFM, an intermingling of TiO2 and PEDOT:PSS at the surface. Variation of TiO2 within the material led to a trade-off in optical and electrical properties. A proof of concept free-standing electrochromic device was fabricated by casting several layers, which was found to be stable over 100 cycles.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-122020 (URN)
Available from: 2015-10-16 Created: 2015-10-16 Last updated: 2017-02-03Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9879-3915

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