Ethylenedioxythiophene‐Based Small Molecular Donor with Multiple Conformation Locks for Organic Solar Cells with Efficiency of 19.3 %

Abstract Ternary organic solar cells (T‐OSCs) represent an efficient strategy for enhancing the performance of OSCs. Presently, the majority of high‐performance T‐OSCs incorporates well‐established Y‐acceptors or donor polymers as the third component. In this study, a novel class of conjugated small molecules has been introduced as the third component, demonstrating exceptional photovoltaic performance in T‐OSCs. This innovative molecule comprises ethylenedioxythiophene (EDOT) bridge and 3‐ethylrhodanine as the end group, with the EDOT unit facilitating the creation of multiple conformation locks. Consequently, the EDOT‐based molecule exhibits two‐dimensional charge transport, distinguishing it from the thiophene‐bridged small molecule, which displays fewer conformation locks and provides one‐dimensional charge transport. Furthermore, the robust electron‐donating nature of EDOT imparts the small molecule with cascade energy levels relative to the electron donor and acceptor. As a result, OSCs incorporating the EDOT‐based small molecule as the third component demonstrate enhanced mobilities, yielding a remarkable efficiency of 19.3 %, surpassing the efficiency of 18.7 % observed for OSCs incorporating thiophene‐based small molecule as the third component. The investigations in this study underscore the excellence of EDOT as a building block for constructing conjugated materials with multiple conformation locks and high charge carrier mobilities, thereby contributing to elevated photovoltaic performance in OSCs.