Backbone rigidity promoting hole delocalization and enabling efficient charge generation with minimal voltage loss in nonfullerene organic photovoltaics

Achieving both low voltage loss and efficient charge generation remains a major challenge in advancing high-performance organic photovoltaics (OPVs). Here, we show that photovoltaic cells using PTNT1-F—a dithienonaphthobisthiadiazole (TNT)-based polymer recently developed by our group—exhibit a notably low nonradiative voltage loss (∆Vnr) of 0.18 V, suggesting a minimal driving force for charge generation. Remarkably, when combined with a nonfullerene acceptor Y12, the PTNT1-F device achieved high photocurrents and charge generation efficiencies exceeding 80% of the theoretical limit—to the best of our knowledge, the highest reported for OPVs with similarly low ∆Vnr. PTNT1-F features a rigid, ordered backbone that preserves the density of states (DOS) upon blending with the acceptor. In contrast, reference polymers such as D18 and PM6 show significant DOS changes, emphasizing advantage of PTNT1-F in promoting hole delocalization and efficient charge dissociation even with limited driving force. These results offer valuable insights into designing polymer donors for simultaneous low voltage loss and efficient charge generation. Achieving low voltage loss and efficient charge generation is crucial for advancing high-performance organic photovoltaics. Here, the authors demonstrate that PTNT1-F, a polymer which they recently developed, achieves a low nonradiative voltage loss and high charge generation efficiency, offering insights into designing polymer donors for improved organic photovoltaics performance.