A Selenium‐Containing Polymer Donor Enables 16.9% Efficiency in Non‐Fused Electron Acceptor‐Based Organic Photovoltaic Cells

Organic photovoltaic cells (OPVs) based on non‐fused electron acceptors (nfEAs) have exhibited substantial progress in enhancing the power conversion efficiency (PCE). However, controlling the morphology of the donor/acceptor blend remains a significant challenge, making the regulation of film formation kinetics crucial. Here, by designing a new selenium‐containing polymer donor PQSe‐TCl, the pre‐aggregation behavior is modulated and finely tune the resultant morphologies. Compared with its thiophene analogue PBQx‐TCl, PQSe‐TCl exhibits a larger π–π stacking distance and weaker pre‐aggregation performance, leading to a longer film‐formation duration in the fabrication process. Consequently, the PQSe‐TCl:A4T‐16‐based device records an outstanding PCE of 16.9%, which is the highest value for fully nfEA‐based OPVs. This study highlights the importance of regulating the film‐formation kinetics for obtaining high‐efficiency nfEA‐based OPVs.