TY  - JOUR
A1  - Gorenflot, Julien
A1  - Paulke, Andreas
A1  - Piersimoni, Fortunato
A1  - Wolf, Jannic
A1  - Kan, Zhipeng
A1  - Cruciani, Federico
A1  - El Labban, Abdulrahman
A1  - Neher, Dieter
A1  - Beaujuge, Pierre M.
A1  - Laquai, Frederic
T1  - From recombination dynamics to device performance
BT  - quantifying the efficiency of exciton dissociation, charge separation, and extraction in bulk heterojunction solar cells with Fluorine-Substituted polymer donors
JF  - dvanced energy materials
N2  - An original set of experimental and modeling tools is used to quantify the yield of each of the physical processes leading to photocurrent generation in organic bulk heterojunction solar cells, enabling evaluation of materials and processing condition beyond the trivial comparison of device performances. Transient absorption spectroscopy, “the” technique to monitor all intermediate states over the entire relevant timescale, is combined with time-delayed collection field experiments, transfer matrix simulations, spectral deconvolution, and parametrization of the charge carrier recombination by a two-pool model, allowing quantification of densities of excitons and charges and extrapolation of their kinetics to device-relevant conditions. Photon absorption, charge transfer, charge separation, and charge extraction are all quantified for two recently developed wide-bandgap donor polymers: poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-difluorothiophene) (PBDT[2F]T) and its nonfluorinated counterpart poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-thiophene) (PBDT[2H]T) combined with PC71BM in bulk heterojunctions. The product of these yields is shown to agree well with the devices' external quantum efficiency. This methodology elucidates in the specific case studied here the origin of improved photocurrents obtained when using PBDT[2F]T instead of PBDT[2H]T as well as upon using solvent additives. Furthermore, a higher charge transfer (CT)-state energy is shown to lead to significantly lower energy losses (resulting in higher VOC) during charge generation compared to P3HT:PCBM.
KW  - bulk heterojunction
KW  - charge generation yield
KW  - charge recombination yield
KW  - polymer solar cells
KW  - transient absorption spectroscopy
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201701678
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 4
PB  - Wiley-VCH
CY  - Weinheim
ER  -