An efficient, "burn in" free organic solar cell employing a nonfullerene electron acceptor

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Title: An efficient, "burn in" free organic solar cell employing a nonfullerene electron acceptor
Authors: Cha, H
Wu, J
Wadsworth, A
Nagitta, J
Limbu, S
Pont, S
Li, Z
Searle, J
Wyatt, MF
Baran, D
Kim, J-S
McCulloch, I
Durrant, JR
Item Type: Journal Article
Abstract: A comparison of the efficiency, stability, and photophysics of organic solar cells employing poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3'″-di(2-octyldodecyl)-2,2';5',2″;5″,2'″-quaterthiophen-5,5'″-diyl)] (PffBT4T-2OD) as a donor polymer blended with either the nonfullerene acceptor EH-IDTBR or the fullerene derivative, [6,6]-phenyl C71 butyric acid methyl ester (PC71 BM) as electron acceptors is reported. Inverted PffBT4T-2OD:EH-IDTBR blend solar cell fabricated without any processing additive achieves power conversion efficiencies (PCEs) of 9.5 ± 0.2%. The devices exhibit a high open circuit voltage of 1.08 ± 0.01 V, attributed to the high lowest unoccupied molecular orbital (LUMO) level of EH-IDTBR. Photoluminescence quenching and transient absorption data are employed to elucidate the ultrafast kinetics and efficiencies of charge separation in both blends, with PffBT4T-2OD exciton diffusion kinetics within polymer domains, and geminate recombination losses following exciton separation being identified as key factors determining the efficiency of photocurrent generation. Remarkably, while encapsulated PffBT4T-2OD:PC71 BM solar cells show significant efficiency loss under simulated solar irradiation ("burn in" degradation) due to the trap-assisted recombination through increased photoinduced trap states, PffBT4T-2OD:EH-IDTBR solar cell shows negligible burn in efficiency loss. Furthermore, PffBT4T-2OD:EH-IDTBR solar cells are found to be substantially more stable under 85 °C thermal stress than PffBT4T-2OD:PC71 BM devices.
Issue Date: 28-Jun-2017
Date of Acceptance: 28-Apr-2017
ISSN: 0935-9648
Publisher: Wiley
Journal / Book Title: Advanced Materials
Volume: 29
Issue: 33
Copyright Statement: © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This is the accepted version of the following article, which has been published in final form at
Sponsor/Funder: Engineering and Physical Sciences Research Council
Funder's Grant Number: EP/L016702/1
Keywords: charge separation
nonfullerene acceptors
organic solar cells
trap assisted recombination
02 Physical Sciences
03 Chemical Sciences
09 Engineering
Nanoscience & Nanotechnology
Publication Status: Published
Conference Place: Germany
Article Number: 1701156
Appears in Collections:Physics
Experimental Solid State
Faculty of Natural Sciences

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