Interactions between nonfullerene acceptors lead to unstable ternary organic photovoltaic cells

Journal Article · Tue May 30 00:00:00 EDT 2023 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.2301118120· OSTI ID:2001353

Li, Yongxi ^[1]; Huang, Xinjing ^[2]; Mencke, Austin R. ^[3]; Kandappa, Sunil Kumar ^[3]; Wang, Tonghui ^[4]; Ding, Kan ^[5]; Jiang, Zuo-Quan ^[6]; Amassian, Aram ^[4]; Liao, Liang-Sheng ^[6]; Thompson, Mark E. ^[3]; Forrest, Stephen R. ^[7]

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1. Department of Electrical Engineering, University of Michigan, Ann Arbor, MI 48109
2. Applied Physics Program, University of Michigan, Ann Arbor, MI 48109
3. Department of Chemistry, University of Southern California, Los Angeles, CA 90089
4. Department of Materials Science and Engineering, and Organic and Carbon Electronic Laboratories, North Carolina State University, Raleigh, NC 27606
5. Department of Physics, University of Michigan, Ann Arbor, MI 48109
6. Institute of Functional Nano &, Soft Materials, Soochow University, Suzhou 215123, China
7. Department of Electrical Engineering, University of Michigan, Ann Arbor, MI 48109, Applied Physics Program, University of Michigan, Ann Arbor, MI 48109, Department of Physics, University of Michigan, Ann Arbor, MI 48109

For organic photovoltaic (OPV) devices to achieve consistent performance and long operational lifetimes, organic semiconductors must be processed with precise control over their purity, composition, and structure. This is particularly important for high volume solar cell manufacturing where control of materials quality has a direct impact on yield and cost. Ternary-blend OPVs containing two acceptor–donor–acceptor (A–D–A)-type nonfullerene acceptors (NFAs) and a donor have proven to be an effective strategy to improve solar spectral coverage and reduce energy losses beyond that of binary-blend OPVs. Here, we show that the purity of such a ternary is compromised during blending to form a homogeneously mixed bulk heterojunction thin film. We find that the impurities originate from end-capping C=C/C=C exchange reactions of A–D–A-type NFAs, and that their presence influences both device reproducibility and long-term reliability. The end-capping exchange results in generation of up to four impurity constituents with strong dipolar character that interfere with the photoinduced charge transfer process, leading to reduced charge generation efficiency, morphological instabilities, and an increased vulnerability to photodegradation. As a consequence, the OPV efficiency falls to less than 65% of its initial value within 265 h when exposed to up to 10 suns intensity illumination. We propose potential molecular design strategies critical to enhancing the reproducibility as well as reliability of ternary OPVs by avoiding end-capping reactions.

• Sponsoring Organization: USDOE
• Grant/Contract Number: EE0008561
• OSTI ID: 2001353
• Alternate ID(s): OSTI ID: 1993002
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 23 Vol. 120; ISSN 0027-8424
• Publisher: Proceedings of the National Academy of Sciences
• Country of Publication: United States
• Language: English