Spooner, E.L.K. orcid.org/0000-0001-9575-550X, Kilbride, R.C. orcid.org/0000-0002-3985-923X, Cai, J. et al. (9 more authors) (2025) Uncovering s-shaped IV curves in organic photovoltaics: The role of DIO-driven vertical segregation. ACS Applied Materials & Interfaces. ISSN 1944-8244
Abstract
Controlling vertical segregation in organic photovoltaics (OPVs) is critical for achieving optimal solar cell performance and stability, requiring careful consideration of a range of factors such as the surface energy and miscibility of components, solvent and solvent additive identity, and film processing methods. In this work, we use neutron reflectivity to compare vertical segregation in two different OPV systems: a fullerene-based system (PBDB-T:PC71BM) and a non-fullerene-based system (PBDB-T:ITIC), processed with different amounts of the solvent additive, 1,8-diiodooctane (DIO). Both systems exhibit vertical segregation, with enrichment of the acceptor at the film/hole transport layer interface. However, the segregation is considerably more pronounced in ITIC-based systems, where the enriched interface consists of pure ITIC, compared to a maximum of 67% PC71BM by volume in the former system. Prolonging film drying with higher solvent additive content exacerbates segregation in both systems, increasing interfacial acceptor concentration in PC71BM systems and broadening the buried interface in ITIC systems. Simulations confirm that extreme vertical segregation in ITIC-based devices induces nonideal ‘s-shaped’ JV curves when the enriched layer is pure and sufficiently thick, as seen in both fresh and aged devices. Our findings highlight that improper vertical segregation not only leads to poor device performance in fresh devices, but gradual segregation can also contribute to morphological degradation and device instabilities over time.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2025 American Chemical Society. This is an author-produced version of a paper subsequently published in ACS Applied Materials & Interfaces. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | organic photovoltaics; stability; morphology; bulk heterojunction; solvent additives; vertical segregation |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematical and Physical Sciences |
Funding Information: | Funder Grant number ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/V055127/1 ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/V027131/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 05 Jun 2025 08:55 |
Last Modified: | 05 Jun 2025 08:55 |
Status: | Published online |
Publisher: | American Chemical Society (ACS) |
Refereed: | Yes |
Identification Number: | 10.1021/acsami.5c04713 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:227461 |
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Filename: Uncovering_S-Shaped_IV_curves_in_Organic_Photovoltaics.pdf
