Ternary Organic Solar Cells with Small Nonradiative Recombination Loss

Nonradiative recombination loss (qΔVocnonrad), as a large component of energy loss (E_loss), has become an important factor that limits the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, high-performance ternary OSCs based on a polymer donor PTB7-Th, a polymer donor PBDTm-T1, and a nonfullerene acceptor FOIC are reported. When blended with FOIC, the PBDTm-T1-based device yielded a smallest qΔVocnonrad of 0.197 eV, but with a moderate PCE of 3.3%. In contrast, the PTB7-Th:FOIC device exhibited a relatively higher qΔVocnonrad of 0.329 eV; however, a high PCE of 11.9% was found. This trade-off relationship has been resolved using a ternary blend. By incorporation of 20% PBDTm-T1 into the PTB7-Th:FOIC blend, a small qΔVocnonrad value of 0.271 eV and a significantly high PCE of 13.8% were simultaneously obtained. The results demonstrate that the nonradiative recombination loss can be effectively reduced by using a ternary strategy.