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Zuo, G., Li, Z., Wang, E. & Kemerink, M. (2018). High Seebeck Coefficient and Power Factor in n-Type Organic Thermoelectrics. ADVANCED ELECTRONIC MATERIALS, 4(1), Article ID 1700501.
Open this publication in new window or tab >>High Seebeck Coefficient and Power Factor in n-Type Organic Thermoelectrics
2018 (English)In: ADVANCED ELECTRONIC MATERIALS, ISSN 2199-160X, Vol. 4, no 1, article id 1700501Article in journal (Refereed) Published
Abstract [en]

The n-type thermoelectric properties of [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) are investigated for different solution-based doping methods. A novel inverse-sequential doping method where the semiconductor (PCBM) is deposited on a previously cast dopant 4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)-N,N-diphenylaniline film to achieve a very high power factor PF approximate to 35 mu W m(-1) K-2 with a conductivity sigma approximate to 40 S m(-1) is introduced. It is also shown that n-type organic semiconductors obey the -1/4 power law relation between Seebeck coefficient S and sigma that are previously found for p-type materials. An analytical model on basis of variable range hopping unifies these results. The power law for n-type materials is shifted toward higher conductivities by two orders of magnitude with respect to that of p-type, suggesting strongly that n-type organic semiconductors can eventually become superior to their p-type counterparts. Adding a small fraction lower lowest unoccupied molecular orbital material (core-cyanated naphthalene diimide) into PCBM leads to a higher S for inverse-sequential doping but not for bulk doping due to different morphologies.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2018
Keywords
n-type doping; organic thermoelectrics; power factor; Seebeck coefficient
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-144566 (URN)10.1002/aelm.201700501 (DOI)000419670400026 ()
Note

Funding Agencies|Chinese Scholarship Council (CSC)

Available from: 2018-01-29 Created: 2018-01-29 Last updated: 2018-05-14
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
Zuo, G., Andersson, O., Abdalla, H. & Kemerink, M. (2018). High thermoelectric power factor from multilayer solution-processed organic films. Applied Physics Letters, 112(8), Article ID 083303.
Open this publication in new window or tab >>High thermoelectric power factor from multilayer solution-processed organic films
2018 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 8, article id 083303Article in journal (Refereed) Published
Abstract [en]

We investigate the suitability of the "sequential doping" method of organic semiconductors for thermoelectric applications. The method consists of depositing a dopant (F4TCNQ) containing solution on a previously cast semiconductor (P3HT) thin film to achieve high conductivity, while preserving the morphology. For very thin films (similar to 25 nm), we achieve a high power factor around 8 mu W/mK(-2) with a conductivity over 500 S/m. For the increasing film thickness, conductivity and power factor show a decreasing trend, which we attribute to the inability to dope the deeper parts of the film. Since thick films are required to extract significant power from thermoelectric generators, we developed a simple additive technique that allows the deposition of an arbitrary number of layers without significant loss in conductivity or power factor that, for 5 subsequent layers, remain at similar to 300 S/m and similar to 5 mu W/mK(-2), respectively, whereas the power output increases almost one order of magnitude as compared to a single layer. The efficient doping in multilayers is further confirmed by an increased intensity of (bi)polaronic features in the UV-Vis spectra. Published by AIP Publishing.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-145764 (URN)10.1063/1.5016908 (DOI)000425977500021 ()
Note

Funding Agencies|China Scholarship Council (CSC); Knut och Alice Wallenbergs stiftelse (Project "Tail of the Sun")

Available from: 2018-03-22 Created: 2018-03-22 Last updated: 2018-05-14
Melianas, A., Pranculis, V., Spoltore, D., Benduhn, J., Inganäs, O., Gulbinas, V., . . . Kemerink, M. (2017). Charge Transport in Pure and Mixed Phases in Organic Solar Cells. Advanced Energy Materials, 7(20)
Open this publication in new window or tab >>Charge Transport in Pure and Mixed Phases in Organic Solar Cells
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2017 (English)In: Advanced Energy Materials, ISSN 1614-6840, Vol. 7, no 20Article in journal (Refereed) Published
Abstract [en]

In organic solar cells continuous donor and acceptor networks are considered necessary for charge extraction, whereas discontinuous neat phases and molecularly mixed donor–acceptor phases are generally regarded as detrimental. However, the impact of different levels of domain continuity, purity, and donor–acceptor mixing on charge transport remains only semiquantitatively described. Here, cosublimed donor–acceptor mixtures, where the distance between the donor sites is varied in a controlled manner from homogeneously diluted donor sites to a continuous donor network are studied. Using transient measurements, spanning from sub-picoseconds to microseconds photogenerated charge motion is measured in complete photovoltaic devices, to show that even highly diluted donor sites (5.7%–10% molar) in a buckminsterfullerene matrix enable hole transport. Hopping between isolated donor sites can occur by long-range hole tunneling through several buckminsterfullerene molecules, over distances of up to ≈4 nm. Hence, these results question the relevance of “pristine” phases and whether a continuous interpenetrating donor–acceptor network is the ideal morphology for charge transport.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
charge carrier transport, fullerene domains, low donor concentration, organic photovoltaics, tunneling
National Category
Physical Chemistry Condensed Matter Physics Biophysics Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:liu:diva-139690 (URN)10.1002/aenm.201700888 (DOI)000413695300018 ()
Note

Funding agencies: German Federal Ministry for Education and Research (BMBF) through the InnoProfille project "Organische p-i-n Bauelemente 2.2"; Research Council of Lithuania [MIP-85/2015]; Science Council of Sweden; Knut and Alice Wallenberg foundation; Wallenberg Scholar

Available from: 2017-08-09 Created: 2017-08-09 Last updated: 2017-11-13Bibliographically approved
Garcia-Iglesias, M., de Waal, B. F. M., Gorbunov, A. V., Palmans, A. R. A., Kemerink, M. & Meijer, E. W. (2016). A Versatile Method for the Preparation of Ferroelectric Supramolecular Materials via Radical End-Functionalization of Vinylidene Fluoride Oligomers. Journal of the American Chemical Society, 138(19), 6217-6223
Open this publication in new window or tab >>A Versatile Method for the Preparation of Ferroelectric Supramolecular Materials via Radical End-Functionalization of Vinylidene Fluoride Oligomers
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2016 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 19, p. 6217-6223Article in journal (Refereed) Published
Abstract [en]

A synthetic method for the end-functionalization of vinylidene fluoride oligomers (OVDF) via a radical reaction between terminal olefins and I-OVDF is described. The method shows a wide substrate scope and excellent conversions, and permits the preparation of different disc-shaped cores such as benzene-1,3,5-tricarboxamides (BTAs), perylenes bisimide and phthalocyanines (Pc) bearing three to eight ferroelectric oligomers at their periphery. The formation, purity, OVDF conformation, and morphology of the final adducts has been assessed by a combination of techniques, such as NMR, size exclusion chromatography, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy. Finally, PBI-OVDF and Pc-OVDF materials show ferroelectric hysteresis behavior together with high remnant polarizations, with values as high as P-r approximate to 37 mC/m(2) for Pc-OVDF. This work demonstrates the potential of preparing a new set of ferroelectric materials simply by attaching OVDF oligomers to different small molecules. The use of carefully chosen small molecules paves the way to new functional materials in which ferroelectricity and electrical conductivity or light-harvesting properties coexist in a single compound.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
National Category
Organic Chemistry
Identifiers
urn:nbn:se:liu:diva-129159 (URN)10.1021/jacs.6b01908 (DOI)000376331000023 ()27119732 (PubMedID)
Note

Funding Agencies|Dutch Polymer Institute (DPI) [765]; Dutch Ministry of Education, Culture and Science [024.001.035]; European Research Council [246829]

Available from: 2016-06-13 Created: 2016-06-13 Last updated: 2017-11-28
Khikhlovskyi, V., van Breemen, A. J. J., Janssen, R. A. J., Gelinck, G. H. & Kemerink, M. (2016). Data retention in organic ferroelectric resistive switches. Organic electronics, 31, 56-62
Open this publication in new window or tab >>Data retention in organic ferroelectric resistive switches
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2016 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 31, p. 56-62Article in journal (Refereed) Published
Abstract [en]

Solution-processed organic ferroelectric resistive switches could become the long-missing non-volatile memory elements in organic electronic devices. To this end, data retention in these devices should be characterized, understood and controlled. First, it is shown that the measurement protocol can strongly affect the apparent retention time and a suitable protocol is identified. Second, it is shown by experimental and theoretical methods that partial depolarization of the ferroelectric is the major mechanism responsible for imperfect data retention. This depolarization occurs in close vicinity to the semiconductor-ferroelectric interface, is driven by energy minimization and is inherently present in this type of phase-separated polymer blends. Third, a direct relation between data retention and the charge injection barrier height of the resistive switch is demonstrated experimentally and numerically. Tuning the injection barrier height allows to improve retention by many orders of magnitude in time, albeit at the cost of a reduced on/off ratio. (c) 2016 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Memories; Data retention; Resistive switching; Organic electronics; Ferroelectrics
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-126799 (URN)10.1016/j.orgel.2016.01.016 (DOI)000371802000008 ()
Note

Funding Agencies|European Community [248092]

Available from: 2016-04-07 Created: 2016-04-05 Last updated: 2017-11-30
Zuo, G., Abdalla, H. & Kemerink, M. (2016). Impact of doping on the density of states and the mobility in organic semiconductors. PHYSICAL REVIEW B, 93(23), 235203
Open this publication in new window or tab >>Impact of doping on the density of states and the mobility in organic semiconductors
2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 23, p. 235203-Article in journal (Refereed) Published
Abstract [en]

We experimentally investigated conductivity and mobility of poly(3-hexylthiophene) (P3HT) doped with tetrafluorotetracyanoquinodimethane (F(4)TCNQ) for various relative doping concentrations ranging from ultralow (10(-5)) to high (10(-1)) and various active layer thicknesses. Although the measured conductivity monotonously increases with increasing doping concentration, the mobilities decrease, in agreement with previously published work. Additionally, we developed a simple yet quantitative model to rationalize the results on basis of a modification of the density of states (DOS) by the Coulomb potentials of ionized dopants. The DOS was integrated in a three-dimensional (3D) hopping formalism in which parameters such as energetic disorder, intersite distance, energy level difference, and temperature were varied. We compared predictions of our model as well as those of a previously developed model to kinetic Monte Carlo (MC) modeling and found that only the former model accurately reproduces the mobility of MC modeling in a large part of the parameter space. Importantly, both our model and MC simulations are in good agreement with experiments; the crucial ingredient to both is the formation of a deep trap tail in the Gaussian DOS with increasing doping concentration.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2016
National Category
Other Physics Topics
Identifiers
urn:nbn:se:liu:diva-130276 (URN)10.1103/PhysRevB.93.235203 (DOI)000378813800009 ()
Note

Funding Agencies|Chinese Scholarship Council (CSC)

Available from: 2016-08-01 Created: 2016-07-28 Last updated: 2018-08-29
Felekidis, N., Wang, E. & Kemerink, M. (2016). Open circuit voltage and efficiency in ternary organic photovoltaic blends. Energy & Environmental Science, 9(1), 257-266
Open this publication in new window or tab >>Open circuit voltage and efficiency in ternary organic photovoltaic blends
2016 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 1, p. 257-266Article in journal (Refereed) Published
Abstract [en]

Organic bulk heterojunction solar cells based on ternary blends of two donor absorbers and one acceptor are investigated by experiments and modeling. The commonly observed continuous tunability of the open circuit voltage V-OC with the donor1 : donor2 ratio can quantitatively be explained as quasi-Fermi level splitting due to photocreated charges filling a joint density of states that is broadened by Gaussian disorder. On this basis, a predictive model for the power conversion efficiency that accounts for the composition-dependent absorption and the shape of the current-voltage characteristic curve is developed. When all other parameters, most notably the fill factor, are constant, we find that for state-of-the-art absorbers, having a broad and strong absorption spectrum, ternary blends offer no advantage over binary ones. For absorbers with a more narrow absorption spectrum ternary blends of donors with complementary absorption spectra, offer modest improvements over binary ones. In contrast, when, upon blending, transport and/or recombination kinetics are improved, leading to an increased fill factor, ternaries may offer significant advantages over binaries.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-124474 (URN)10.1039/c5ee03095a (DOI)000367622700030 ()
Note

Funding Agencies|Swedish Research Council

Available from: 2016-02-02 Created: 2016-02-01 Last updated: 2018-09-10
Lee, J., van Breemen, A. J. J., Khikhlovskyi, V., Kemerink, M., Janssen, R. A. J. & Gelinck, G. H. (2016). Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode. Scientific Reports, 6(24407)
Open this publication in new window or tab >>Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode
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2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, no 24407Article in journal (Refereed) Published
Abstract [en]

We demonstrate multilevel data storage in organic ferroelectric resistive memory diodes consisting of a phase-separated blend of P(VDF-TrFE) and a semiconducting polymer. The dynamic behaviour of the organic ferroelectric memory diode can be described in terms of the inhomogeneous field mechanism (IFM) model where the ferroelectric components are regarded as an assembly of randomly distributed regions with independent polarisation kinetics governed by a time-dependent local field. This allows us to write and non-destructively read stable multilevel polarisation states in the organic memory diode using controlled programming pulses. The resulting 2-bit data storage per memory element doubles the storage density of the organic ferroelectric resistive memory diode without increasing its technological complexity, thus reducing the cost per bit.

Place, publisher, year, edition, pages
Nature Publishing Group, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-127745 (URN)10.1038/srep24407 (DOI)000374166100001 ()27080264 (PubMedID)
Note

Funding Agencies|Research Grant of Pukyong National University [CD20151148]

Available from: 2016-05-12 Created: 2016-05-12 Last updated: 2017-11-30
Gorbunov, A. V., Haedler, A. T., Putzeys, T., Zha, R. H., Schmidt, H.-W., Kivala, M., . . . Kemerink, M. (2016). Switchable Charge Injection Barrier in an Organic Supramolecular Semiconductor. ACS Applied Materials and Interfaces, 8(24), 15535-15542
Open this publication in new window or tab >>Switchable Charge Injection Barrier in an Organic Supramolecular Semiconductor
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2016 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 24, p. 15535-15542Article in journal (Refereed) Published
Abstract [en]

We disclose a supramolecular material that combines semiconducting and dipolar functionalities. The material consists of a discotic semiconducting carbonyl-bridged triarylamine core, which is surrounded by three dipolar amide groups. In thin films, the material self-organizes in a hexagonal columnar fashion through Jr-stacking of the molecular core and hydrogen bonding between the amide groups. Alignment by an electrical field in a simple metal/semiconductor/metal geometry induces a polar order in the interface layers near the metal contacts that can be reversibly switched, while the bulk material remains nonpolarized. On suitably chosen electrodes, the presence of an interfacial polarization field leads to a modulation of the barrier for charge injection into the semiconductor. Consequently, a reversible switching is possible between a high-resistance, injection-limited off-state and a low-resistance, space-charge-limited on-state. The resulting memory diode shows switchable rectification with on/off ratios of up to two orders of magnitude. This demonstrated multifunctionality of a single material is a promising concept toward possible application in lowcost, large-area, nonvolatile organic memories.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
Keywords
organic semiconductors; current switching; memories; polarization; rectification; dipolar switching; injection barrier
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-130278 (URN)10.1021/acsami.6b02988 (DOI)000378584800072 ()27246280 (PubMedID)
Note

Funding Agencies|NWO Nano program; Bavarian State Ministry of Science, Research, and the Arts for the Collaborative Research Network Solar Technologies go Hybrid; Deutsche Forschungsgemeinschaft (DFG) [SFB 953]; Vetenskapsradet [2015-03813]

Available from: 2016-08-01 Created: 2016-07-28 Last updated: 2017-11-28
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7104-7127

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