TY  - JOUR
A1  - Albrecht, Steve
A1  - Schindler, Wolfram
A1  - Kurpiers, Jona
A1  - Kniepert, Juliane
A1  - Blakesley, James C.
A1  - Dumsch, Ines
A1  - Allard, Sybille
A1  - Fostiropoulos, Konstantinos
A1  - Scherf, Ullrich
A1  - Neher, Dieter
T1  - On the field dependence of free charge carrier generation and recombination in blends of PCPDTBT/PC70BM influence of solvent additives
JF  - The journal of physical chemistry letters
N2  - We have applied time-delayed collection field (TDCF) and charge extraction by linearly increasing voltage (CELIV) to investigate the photogeneration, transport, and recombination of charge carriers in blends composed of PCPDTBT/PC70BM processed with and without the solvent additive diiodooctane. The results suggest that the solvent additive has severe impacts on the elementary processes involved in the photon to collected electron conversion in these blends. First, a pronounced field dependence of the free carrier generation is found for both blends, where the field dependence is stronger without the additive. Second, the fate of charge carriers in both blends can be described with a rather high bimolecular recombination coefficients, which increase with decreasing internal field. Third, the mobility is three to four times higher with the additive. Both blends show a negative field dependence of mobility, which we suggest to cause bias-dependent recombination coefficients.
Y1  - 2012
U6  - https://doi.org/10.1021/jz3000849
SN  - 1948-7185
VL  - 3
IS  - 5
SP  - 640
EP  - 645
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Albrecht, Steve
A1  - Tumbleston, John R.
A1  - Janietz, Silvia
A1  - Dumsch, Ines
A1  - Allard, Sybille
A1  - Scherf, Ullrich
A1  - Ade, Harald W.
A1  - Neher, Dieter
T1  - Quantifying charge extraction in organic solar cells: The case of fluorinated PCPDTBT
JF  - The journal of physical chemistry letters
N2  - We introduce a new and simple method to quantify the effective extraction mobility in organic solar cells at low electric fields and charge carrier densities comparable to operation conditions under one sun illumination. By comparing steady-state carrier densities at constant illumination intensity and under open-circuit conditions, the gradient of the quasi-Fermi potential driving the current is estimated as a function of external bias and charge density. These properties are then related to the respective steady-state current to determine the effective extraction mobility. The new technique is applied to different derivatives of the well-known low-band-gap polymer PCPDTBT blended with PC70BM. We show that the slower average extraction due to lower mobility accounts for the moderate fill factor when solar cells are fabricated with mono- or difluorinated PCPDTBT. This lower extraction competes with improved generation and reduced nongeminate recombination, rendering the monofluorinated derivative the most efficient donor polymer.
Y1  - 2014
U6  - https://doi.org/10.1021/jz500457b
SN  - 1948-7185
VL  - 5
IS  - 7
SP  - 1131
EP  - 1138
PB  - American Chemical Society
CY  - Washington
ER  -