Interactions between nonfullerene acceptors lead to unstable ternary organic photovoltaic cells
Abstract
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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 30, 2023
- Source ID
- 10.1073/pnas.2301118120
Entities
People
- Aram Amassian
- Austin R. Mencke
- Kan Ding
- Liang-Sheng Liao
- Mark Thompson
- Stephen R. Forrest
- Sunil Kumar Kandappa
- Tonghui Wang
- Xinjing Huang
- Yongxi Li
- Zuo-Quan Jiang
Organizations
- North Carolina State University
- Office of Naval Research
- Office of Naval Research Global
- Soochow University
- Universal Display Corporation
- University of Michigan
- University of Southern California