TY  - JOUR
A1  - Lu, Guanghao
A1  - Blakesley, James C.
A1  - Himmelberger, Scott
A1  - Pingel, Patrick
A1  - Frisch, Johannes
A1  - Lieberwirth, Ingo
A1  - Salzmann, Ingo
A1  - Oehzelt, Martin
A1  - Di Pietro, Riccardo
A1  - Salleo, Alberto
A1  - Koch, Norbert
A1  - Neher, Dieter
T1  - Moderate doping leads to high performance of semiconductor/insulator polymer blend transistors
JF  - Nature Communications
N2  - Polymer transistors are being intensively developed for next-generation flexible electronics. Blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix have simultaneously shown superior performance and environmental stability in organic field-effect transistors compared with the neat semiconductor. Here we show that such blends actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping. Structural investigations show that these blend layers feature nanometre-scale semiconductor domains and a vertical composition gradient. This particular morphology enables a quasi three-dimensional spatial distribution of semiconductor pathways within the insulating matrix, in which charge accumulation and depletion via a gate bias is substantially different from neat semiconductor, and where high on-current and low off-current are simultaneously realized in the stable doped state. Adding only 5 wt% of a semiconducting polymer to a polystyrene matrix, we realized an environmentally stable inverter with gain up to 60.
Y1  - 2013
U6  - https://doi.org/10.1038/ncomms2587
SN  - 2041-1723
VL  - 4
IS  - 1-2
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Schubert, Marcel
A1  - Preis, Eduard
A1  - Blakesley, James C.
A1  - Pingel, Patrick
A1  - Scherf, Ullrich
A1  - Neher, Dieter
T1  - Mobility relaxation and electron trapping in a donor/acceptor copolymer
JF  - Physical review : B, Condensed matter and materials physics
N2  - To address the nature of charge transport and the origin of severe (intrinsic) trapping in electron-transporting polymers, transient and steady-state charge transport measurements have been conducted on the prototype donor/acceptor copolymer poly[2,7-(9,9-dialkyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PFTBTT). A charge-generation layer technique is used to selectively address transport of the desired charge carrier type, to perform time-of-flight measurements on samples with < 200 nm thickness, and to combine the time-of-flight and the photocharge extraction by linearly increasing voltage (photo-CELIV) techniques to investigate charge carrier dynamics over a wide time range. Significant trapping of free electrons is observed in the bulk of dioctyl-substituted PFTBTT (alt-PF8TBTT), introducing a strong relaxation of the charge carrier mobility with time. We used Monte-Carlo simulation to simulate the measured transient data and found that all measurements can be modeled with a single parameter set, with the charge transport behavior determined by multiple trapping and detrapping of electrons in an exponential trap distribution. The influence of the concomitant mobility relaxation on the transient photocurrent characteristics in photo-CELIV experiments is discussed and shown to explain subtle features that were seen in former publications but were not yet assigned to electron trapping. Comparable studies on PFTBTT copolymers with chemical modifications of the side chains and backbone suggest that the observed electron trapping is not caused by a distinct chemical species but rather is related to interchain interactions.
Y1  - 2013
U6  - https://doi.org/10.1103/PhysRevB.87.024203
SN  - 1098-0121
VL  - 87
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  -