An analysis of the factors determining the efficiency of photocurrent generation in polymer:nonfullerene acceptor solar cells

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Title: An analysis of the factors determining the efficiency of photocurrent generation in polymer:nonfullerene acceptor solar cells
Authors: Cha, H
Tan, C-H
Wu, J
Dong, Y
Zhang, W
Chen, H
Rajaram, S
Narayan, KS
McCulloch, I
Durrant, JR
Item Type: Journal Article
Abstract: Herein, a meta‐analysis of the device performance and transient spectroscopic results are undertaken for various donor:acceptor blends, employing three different donor polymers and seven different acceptors including nonfullerene acceptors (NFAs). From this analysis, it is found that the primary determinant of device external quantum efficiency (EQE) is the energy offset driving interfacial charge separation, ΔECS. For devices employing the donor polymer PffBT4T blended with NFA and fullerene acceptors, an energy offset ΔECS = 0.30 eV is required to achieve near unity charge separation, which increases for blends with PBDTTT‐EFT and P3HT to 0.36 and ≈1.2 eV, respectively. For blends with PffBT4T and PBDTTT‐EFT, a 100 meV decrease in the LUMO of the acceptor is observed to result in an approximately twofold increase in EQE. Steady state and transient optical data determine that this energy offset requirement is not associated with the need to overcome the polymer exciton binding energy and thereby drive exciton separation, with all blends studied showing efficient exciton separation. Rather, the increase in EQE with larger energy offset is shown to result from suppression of geminate recombination losses. These results are discussed in terms of their implications for the design of donor/NFA interfaces in organic solar cells, and strategies to achieve further advances in device performance.
Issue Date: 15-Nov-2018
Date of Acceptance: 1-Sep-2018
URI: http://hdl.handle.net/10044/1/65082
DOI: https://dx.doi.org/10.1002/aenm.201801537
ISSN: 1614-6832
Publisher: Wiley
Journal / Book Title: Advanced Energy Materials
Volume: 8
Issue: 32
Copyright Statement: © 2018 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. This is the accepted version of the following article: H. Cha, C.‐H. Tan, J. Wu, Y. Dong, W. Zhang, H. Chen, S. Rajaram, K. S. Narayan, I. McCulloch, J. R. Durrant, Adv. Energy Mater. 2018, 8, 1801537, which has been published in final form at https://dx.doi.org/10.1002/aenm.201801537
Sponsor/Funder: Commission of the European Communities
Kaust
Engineering and Physical Sciences Research Council
Funder's Grant Number: 609788
CHEDG_P61719
EP/P032591/1
Keywords: Science & Technology
Physical Sciences
Technology
Chemistry, Physical
Energy & Fuels
Materials Science, Multidisciplinary
Physics, Applied
Physics, Condensed Matter
Chemistry
Materials Science
Physics
charge separation
energy offset
nonfullerene acceptors
photocurrent
transient absorption spectroscopy
GEMINATE RECOMBINATION LOSSES
CHARGE SEPARATION
ORGANIC PHOTOVOLTAICS
NONFULLERENE ACCEPTOR
13-PERCENT EFFICIENCY
ELECTRON-ACCEPTORS
HIGHLY EFFICIENT
DRIVING-FORCE
BAND-GAP
FULLERENE
Publication Status: Published
Embargo Date: 2019-10-01
Article Number: 1801537
Online Publication Date: 2018-10-01
Appears in Collections:Chemistry
Faculty of Natural Sciences



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