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Organic solar cells with near-unity charge generation yield

Wei Li, Stefan Zeiske, Oskar Sandberg Orcid Logo, Drew Riley, Paul Meredith Orcid Logo, Ardalan Armin Orcid Logo

Energy & Environmental Science, Volume: 14, Issue: 12, Pages: 6484 - 6493

Swansea University Authors: Wei Li, Stefan Zeiske, Oskar Sandberg Orcid Logo, Drew Riley, Paul Meredith Orcid Logo, Ardalan Armin Orcid Logo

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DOI (Published version): 10.1039/d1ee01367j

Abstract

The subtle link between photogenerated charge generation yield (CGY) and bimolecular recombination in organic semiconductor-based photovoltaics is relatively well established as a concept but has proven extremely challenging to demonstrate and probe especially under operational conditions. Received...

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Published in: Energy & Environmental Science
ISSN: 1754-5692 1754-5706
Published: Royal Society of Chemistry (RSC) 2021
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa58680
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Abstract: The subtle link between photogenerated charge generation yield (CGY) and bimolecular recombination in organic semiconductor-based photovoltaics is relatively well established as a concept but has proven extremely challenging to demonstrate and probe especially under operational conditions. Received wisdom also teaches that charge generation in excitonic systems will always be lower than non-excitonic semiconductors such as GaAs – but this view is being challenged with the advent of organic semiconductor blends based upon non-fullerene acceptors (NFAs) with power conversion efficiencies exceeding 18%. Using a newly developed approach based upon temperature dependent ultra-sensitive external quantum efficiency measurements, we observe near unity CGY in several model NFA-based systems measured with unprecedented accuracy. We find that a relatively small increase in yield from 0.984 to 0.993 leads to a reduction in bimolecular recombination from 400 times to 1000 times relative to the Langevin limit. In turn, this dramatic reduction delivers the best thick junction performance to date in any binary organic solar cell – notably 16.2% at 300 nm. The combination of high efficiency and thick junction is the key for industrial fabrication of these devices via high-throughput deposition processing such as roll-to-roll, and thus central to a viable solar cell technology. These results also clearly reveal and elucidate the relationship between photo-generation and recombination in excitonic semiconductor photovoltaics thus providing an important bridge between basic device physics and practical cell engineering.
Keywords: Pollution, Nuclear Energy and Engineering, Renewable Energy, Sustainability and the Environment, Environmental Chemistry
College: College of Science
Funders: Engineering and Physical Sciences Research Council Grant: EP/T028511/1 Identifier: FundRef 10.13039/501100000266 Natural Sciences and Engineering Research Council of Canada Grant: PGSD3-545694-2020 Identifier: FundRef 10.13039/501100000038
Issue: 12
Start Page: 6484
End Page: 6493