Inverted all-polymer solar cells based on a quinoxaline-thiophene/naphthalene-diimide polymer blend improved by annealing
Journal article, 2016
We have investigated the effect of thermal annealing on the photovoltaic parameters of all-polymer solar cells based on a quinoxaline-thiophene donor polymer (TQ1) and a naphthalene diimide acceptor polymer (N2200). The annealed devices show a doubled power conversion efficiency compared to nonannealed devices, due to the higher short-circuit current (J(sc)) and fill factor (FF), but with a lower open circuit voltage (V-oc). On the basis of the morphology-mobility examination by several scanning force microscopy techniques, and by grazing-incidence wide-angle X-ray scattering, we conclude that better charge transport is achieved by higher order and better interconnected networks of the bulk heterojunction in the annealed active layers. The annealing improves charge transport and extends the conjugation length of the polymers, which do help in charge generation and meanwhile reduce recombination. Photoluminescence, electroluminescence, and light intensity dependence measurements reveal how this morphological change affects charge generation and recombination. As a result, the J(sc) and FF are significantly improved. However, the smaller band gap and the higher HOMO level of TQ1 upon annealing causes a lower V-oc. The blend of an amorphous polymer TQ1, and a semi-crystalline polymer N2200, can thus be modified by thermal annealing to double the power conversion efficiency.
acceptor
performance
crystallinity
open-circuit voltage
high-mobility
photovoltaics
efficiency
aggregation
morphology
conjugated polymers
Author
Y. X. Xia
Linköping University
Jinan University
C. Musumeci
Linköping University
J. Bergqvist
Linköping University
W. Ma
Xi'an Jiaotong University
F. Gao
Linköping University
Z. Tang
Linköping University
S. Bai
Linköping University
Y. Z. Jin
Zhejiang University
C. H. Zhu
Lawrence Berkeley National Laboratory
Renee Kroon
University of South Australia
C. F. Wang
Lawrence Berkeley National Laboratory
Mats Andersson
University of South Australia
Lintao Hou
Jinan University
Olle Inganäs
Linköping University
Ergang Wang
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Journal of Materials Chemistry A
20507488 (ISSN) 20507496 (eISSN)
Vol. 4 10 3835-3843Subject Categories
Environmental Engineering
Polymer Technologies
DOI
10.1039/c6ta00531d