Unraveling the impacts of intermolecular interaction on morphology evolution for highly efficient organic solar cells and modules

Understanding the effect of intermolecular interaction on the growth dynamic of active layers is critical for advancing organic solar cells (OSCs). However, the diverse structure of donors and acceptors makes the research challenging. Additives with customizable structures and properties could simplify this complexity. Herein, we meticulously tailor two additives of 3,4-ethylenedioxythiophene (EDOT) and 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT), possessing distinct intermolecular interaction features to elaborate the inherent relationship. It is found that varied interaction strengths can alter film formation processes. The enhanced intermolecular interaction between the DBEDOT and non-fullerene acceptor BTP-eC9-4F results in pre-aggregation and longer crystallization duration of BTP-eC9-4F, facilitating the formation of films with compact molecular packing and decent phase separation. Thus, exciton dissociation and charge transport become more efficient. Finally, devices processed with DBEDOT exhibit a remarkable power conversion efficiency of 19.35% in small-area OSCs and 14.11% in blade-coated 5 cm × 5 cm organic solar mini-modules. Especially, OSCs can maintain 80% of their initial efficiency after continuous annealing at 85 °C for over 2,100 h.