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Influence of blend morphology and energetics on charge separation and recombination dynamics in organic solar cells incorporating a nonfullerene acceptor

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Title: Influence of blend morphology and energetics on charge separation and recombination dynamics in organic solar cells incorporating a nonfullerene acceptor
Authors: Cha, H
Wheeler, S
Holliday, S
Dimitrov, SD
Wadsworth, A
Lee, HH
Baran, D
McCulloch, I
Durrant, JR
Item Type: Journal Article
Abstract: Nonfullerene acceptors (NFAs) in blends with highly crystalline donor polymers have been shown to yield particularly high device voltage outputs, but typically more modest quantum yields for photocurrent generation as well as often lower fill factors (FF). In this study, we employ transient optical and optoelectronic analysis to elucidate the factors determining device photocurrent and FF in blends of the highly crystalline donor polymer PffBT4T-2OD with the promising NFA FBR or the more widely studied fullerene acceptor PC71BM. Geminate recombination losses, as measured by ultrafast transient absorption spectroscopy, are observed to be significantly higher for PffBT4T-2OD:FBR blends. This is assigned to the smaller LUMO-LUMO offset of the PffBT4T-2OD:FBR blends relative to PffBT4T-2OD:PC71BM, resulting in the lower photocurrent generation efficiency obtained with FBR. Employing time delayed charge extraction measurements, these geminate recombination losses are observed to be field dependent, resulting in the lower FF observed with PffBT4T-2OD:FBR devices. These data therefore provide a detailed understanding of the impact of acceptor design, and particularly acceptor energetics, on organic solar cell performance. Our study concludes with a discussion of the implications of these results for the design of NFAs in organic solar cells.
Issue Date: 17-Jan-2018
Date of Acceptance: 28-Sep-2017
URI: http://hdl.handle.net/10044/1/64986
DOI: https://dx.doi.org/10.1002/adfm.201704389
ISSN: 1616-301X
Publisher: Wiley
Journal / Book Title: Advanced Functional Materials
Volume: 28
Issue: 3
Copyright Statement: © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This is the pre-peer reviewed version of the article, which has been published in final form at https://dx.doi.org/10.1002/adfm.201704389
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (E
Kaust
Engineering and Physical Sciences Research Council
Funder's Grant Number: EP/J021199/1
EP/M023532/1
CHEDG_P61719
EP/P032591/1
Keywords: Science & Technology
Physical Sciences
Technology
Chemistry, Multidisciplinary
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Physics, Applied
Physics, Condensed Matter
Chemistry
Science & Technology - Other Topics
Materials Science
Physics
field-dependent generation
geminate recombination
nonfullerene acceptors
nongeminate recombination
organic solar cells
NON-FULLERENE
HIGH-EFFICIENCY
GEMINATE RECOMBINATION
ELECTRON-ACCEPTORS
POLYMER
PHOTOVOLTAICS
FILMS
DIFFUSION
MOBILITY
LOSSES
03 Chemical Sciences
09 Engineering
02 Physical Sciences
Materials
Publication Status: Published
Article Number: ARTN 1704389
Online Publication Date: 2017-11-27
Appears in Collections:Chemistry
Faculty of Natural Sciences



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