TY  - JOUR
A1  - Li, Wentao
A1  - Abrecht, Steve
A1  - Yang, Liqiang
A1  - Roland, Steffen
A1  - Tumbleston, John R.
A1  - McAfee, Terry
A1  - Yan, Liang
A1  - Kelly, Mary Allison
A1  - Ade, Harald W.
A1  - Neher, Dieter
A1  - You, Wei
T1  - Mobility-controlled performance of thick solar cells based on fluorinated copolymers
JF  - Journal of the American Chemical Society
N2  - Developing novel materials and device architectures to further enhance the efficiency of polymer solar cells requires a fundamental understanding of the impact of chemical structures on photovoltaic properties. Given that device characteristics depend on many parameters, deriving structureproperty relationships has been very challenging. Here we report that a single parameter, hole mobility, determines the fill factor of several hundred nanometer thick bulk heterojunction photovoltaic devices based on a series of copolymers with varying amount of fluorine substitution. We attribute the steady increase of hole mobility with fluorine content to changes in polymer molecular ordering. Importantly, all other parameters, including the efficiency of free charge generation and the coefficient of nongeminate recombination, are nearly identical. Our work emphasizes the need to achieve high mobility in combination with strongly suppressed charge recombination for the thick devices required by mass production technologies.
Y1  - 2014
U6  - https://doi.org/10.1021/ja5067724
SN  - 0002-7863
VL  - 136
IS  - 44
SP  - 15566
EP  - 15576
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lange, Ilja
A1  - Reiter, Sina
A1  - Paetzel, Michael
A1  - Zykov, Anton
A1  - Nefedov, Alexei
A1  - Hildebrandt, Jana
A1  - Hecht, Stefan
A1  - Kowarik, Stefan
A1  - Woell, Christof
A1  - Heimel, Georg
A1  - Neher, Dieter
T1  - Tuning the work function of polar zinc oxide surfaces using modified phosphonic acid self-assembled monolayers
JF  - Advanced functional materials
N2  - Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self-assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole-injecting and electron-injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well-defined molecular monolayers.
KW  - ZnO
KW  - self-assembled monolayers
KW  - phosphonic acid
KW  - surface modification
KW  - electrodes
Y1  - 2014
U6  - https://doi.org/10.1002/adfm.201401493
SN  - 1616-301X
SN  - 1616-3028
VL  - 24
IS  - 44
SP  - 7014
EP  - 7024
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kraffert, Felix
A1  - Steyrleuthner, Robert
A1  - Albrecht, Steve
A1  - Neher, Dieter
A1  - Scharber, Markus C.
A1  - Bittl, Robert
A1  - Behrends, Jan
T1  - Charge Separation in PCPDTBT : PCBM Blends from an EPR Perspective
JF  - The journal of physical chemistry
Y1  - 2014
U6  - https://doi.org/10.1021/jp509650v
SN  - 1932-7447
VL  - 118
IS  - 49
SP  - 28482
EP  - 28493
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - GEN
A1  - Liu, W.
A1  - Tkachov, R.
A1  - Komber, H.
A1  - Senkovskyy, V.
A1  - Schubert, M.
A1  - Wei, Z.
A1  - Facchetti, A.
A1  - Neher, Dieter
A1  - Kiriy, A.
T1  - Chain-growth polycondensation of perylene diimide-based copolymers
BT  - a new route to regio-regular perylene diimide-based acceptors for all-polymer solar cells and n-type transistors
N2  - Herein, we report the chain-growth tin-free room temperature polymerization method to synthesize n-type perylene diimide-dithiophene-based conjugated polymers (PPDIT2s) suitable for solar cell and transistor applications. The palladium/electron-rich tri-tert-butylphosphine catalyst is effective to enable the chain-growth polymerization of anion-radical monomer Br-TPDIT-Br/Zn to PPDIT2 with a molecular weight up to Mw ≈ 50 kg mol−1 and moderate polydispersity. This is the second example of the polymerization of unusual anion-radical aromatic complexes formed in a reaction of active Zn and electron-deficient diimide-based aryl halides. As such, the discovered polymerization method is not a specific reactivity feature of the naphthalene-diimide derivatives but is rather a general polymerization tool. This is an important finding, given the significantly higher maximum external quantum efficiency that can be reached with PDI-based copolymers (32–45%) in all-polymer solar cells compared to NDI-based materials (15–30%). Our studies revealed that PPDIT2 synthesized by the new method and the previously published polymer prepared by step-growth Stille polycondensation show similar electron mobility and all-polymer solar cell performance. At the same time, the polymerization reported herein has several technological advantages as it proceeds relatively fast at room temperature and does not involve toxic tin-based compounds. Because several chain-growth polymerization reactions are well-suited for the preparation of well-defined multi-functional polymer architectures, the next target is to explore the utility of the discovered polymerization in the synthesis of end-functionalized polymers and block copolymers. Such materials would be helpful to improve the nanoscale morphology of polymer blends in all-polymer solar cells.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 273 
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98724
ER  -