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Influences of Non-fullerene Acceptor Fluorination on Three-Dimensional Morphology and Photovoltaic Properties of Organic Solar Cells

Mengxue Chen, Dan Liu, Wei Li, Robert S. Gurney, Donghui Li, Jinlong Cai, Emma L. K. Spooner, Rachel C. Kilbride, James D. McGettrick, Trystan Watson Orcid Logo, Zhe Li, Richard A. L. Jones, David G. Lidzey, Tao Wang

ACS Applied Materials & Interfaces, Volume: 11, Issue: 29, Pages: 26194 - 26203

Swansea University Author: Trystan Watson Orcid Logo

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DOI (Published version): 10.1021/acsami.9b07317

Abstract

Fluorination of conjugated molecules has been established as an effective structural modification strategy to influence properties and has attracted extensive attention in organic solar cells (OSCs). Here, we have investigated optoelectronic and photovoltaic property changes of OSCs made of polymer...

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Published in: ACS Applied Materials & Interfaces
ISSN: 1944-8244 1944-8252
Published: 2019
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URI: https://cronfa.swan.ac.uk/Record/cronfa51386
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Abstract: Fluorination of conjugated molecules has been established as an effective structural modification strategy to influence properties and has attracted extensive attention in organic solar cells (OSCs). Here, we have investigated optoelectronic and photovoltaic property changes of OSCs made of polymer donors with the non-fullerene acceptors (NFAs) ITIC and IEICO and their fluorinated counterparts IT-4F and IEICO-4F. Device studies show that fluorinated NFAs lead to reduced Voc but increased Jsc and fill-factor (FF), and therefore, the ultimate influence to efficiency depends on the compensation of Voc loss and gains of Jsc and FF. Fluorination lowers energy levels of NFAs, reduces their electronic band gaps, and red-shifts the absorption spectra. The impact of fluorination on the molecular order depends on the specific NFA, and the conversion of ITIC to IT-4F reduces the structural order, which can be reversed after blending with the donor PBDB-T. Contrastingly, IEICO-4F presents stronger π–π stacking after fluorination from IEICO, and this is further strengthened after blending with the donor PTB7-Th. The photovoltaic blends universally present a donor-rich surface region which can promote charge transport and collection toward the anode in inverted OSCs. The fluorination of NFAs, however, reduces the fraction of donors in this donor-rich region, consequently encouraging the intermixing of donor/acceptor for efficient charge generation.
Keywords: organic solar cells, non-fullerene acceptors, fluorination, three-dimensional morphology, photovoltaic properties
College: Faculty of Science and Engineering
Issue: 29
Start Page: 26194
End Page: 26203

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