TY  - JOUR
A1  - Di Pietro, Riccardo
A1  - Erdmann, Tim
A1  - Carpenter, Joshua H.
A1  - Wang, Naixiang
A1  - Shivhare, Rishi Ramdas
A1  - Formanek, Petr
A1  - Heintze, Cornelia
A1  - Voit, Brigitte
A1  - Neher, Dieter
A1  - Ade, Harald W.
A1  - Kiriy, Anton
T1  - Synthesis of High-Crystallinity DPP Polymers with Balanced Electron and Hole Mobility
JF  - Chemistry of materials : a publication of the American Chemical Society
Y1  - 2017
U6  - https://doi.org/10.1021/acs.chemmater.7b04423
SN  - 0897-4756
SN  - 1520-5002
VL  - 29
SP  - 10220
EP  - 10232
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Tremel, Kim
A1  - Fischer, Florian S. U.
A1  - Kayunkid, Navaphun
A1  - Di Pietro, Riccardo
A1  - Tkachov, Roman
A1  - Kiriy, Anton
A1  - Neher, Dieter
A1  - Ludwigs, Sabine
A1  - Brinkmann, Martin
T1  - Charge transport anisotropy in highly oriented thin films of the acceptor polymer P(NDI2OD-T2)
JF  - dvanced energy materials
N2  - The nanomorphology of the high mobility polymer poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} P(NDI2OD-T2) in thin films is explored as a function of different annealing conditions and correlated to optical and electrical properties. While nanofibrils with face-on orientation in form I are obtained directly after spin-coating and annealing below the melt transition temperature, clear evidence of lamellar structures is found after melt-annealing followed by slow cooling to room temperature. Interestingly these structural changes are accompanied by distinct changes in the absorption patterns. Electron diffraction measurements further show clear transitions towards predominant edge-on oriented chains in form II upon melt-annealing. Large-scale alignment with dichroic ratios up to 10 and improved order is achieved by high temperature rubbing and subsequent post-rubbing annealing. These highly oriented morphologies allow anisotropic in-plane charge transport to be probed with top-gate transistors parallel and perpendicular to the polymer chain direction. Mobilities up to 0.1 cm(2) V-1 s(-1) are observed parallel to the polymer chain, which is up to 10 times higher than those perpendicular to the polymer chain.
Y1  - 2014
U6  - https://doi.org/10.1002/aenm.201301659
SN  - 1614-6832
SN  - 1614-6840
VL  - 4
IS  - 10
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Shivhare, Rishi
A1  - Erdmann, Tim
A1  - Hoermann, Ulrich
A1  - Collado-Fregoso, Elisa
A1  - Zeiske, Stefan
A1  - Benduhn, Johannes
A1  - Ullbrich, Sascha
A1  - Huebner, Rene
A1  - Hambsch, Mike
A1  - Kiriy, Anton
A1  - Voit, Brigitte
A1  - Neher, Dieter
A1  - Vandewal, Koen
A1  - Mannsfeld, Stefan C. B.
T1  - Alkyl Branching Position in Diketopyrrolopyrrole Polymers
BT  - Interplay between Fibrillar Morphology and Crystallinity and Their Effect on Photogeneration and Recombination in Bulk-Heterojunction Solar Cells
JF  - Chemistry of materials : a publication of the American Chemical Society
N2  - Diketopyrrolopyrrole (DPP)-based donor acceptor copolymers have gained a significant amount of research interest in the organic electronics community because of their high charge carrier mobilities in organic field-effect transistors (OFETs) and their ability to harvest near-infrared (NIR) photons in solar cells. In this study, we have synthesized four DPP based donor-acceptor copolymers with variations in the donor unit and the branching point of the solubilizing alkyl chains (at the second or sixth carbon position). Grazing incidence wide-angle X-ray scattering (GIWAXS) results suggest that moving the branching point further away from the polymer backbone increases the tendency for aggregation and yields polymer phases with a higher degree of crystallinity (DoC). The polymers were blended with PC70BM and used as active layers in solar cells. A careful analysis of the energetics of the neat polymer and blend films reveals that the charge-transfer state energy (E-CT) of the blend films lies exceptionally close to the singlet energy of the donor (E-D*), indicating near zero electron transfer losses. The difference between the optical gap and open-circuit voltage (V-OC) is therefore determined to be due to rather high nonradiative 418 +/- 13 mV) and unavoidable radiative voltage losses (approximate to 255 +/- 8 mV). Even though the four materials have similar optical gaps, the short-circuit current density (J(SC)) covers a vast span from 7 to 18 mA cm(-2) for the best performing system. Using photoluminescence (PL) quenching and transient charge extraction techniques, we quantify geminate and nongeminate losses and find that fewer excitons reach the donor-acceptor interface in polymers with further away branching points due to larger aggregate sizes. In these material systems, the photogeneration is therefore mainly limited by exciton harvesting efficiency.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.chemmater.8b02739
SN  - 0897-4756
SN  - 1520-5002
VL  - 30
IS  - 19
SP  - 6801
EP  - 6809
PB  - American Chemical Society
CY  - Washington
ER  -