UV-Absorbing Energy Transfer and Morphology Regulation by D-A-Type Integrated Additives for Stable and Efficient Organic Solar Cells.

Organic solar cells (OSCs) face persistent challenges in maintaining both high efficiency and operational stability. Here, we report a rational design of D-A-type additives (UV326-DBOPA and UV327-DBOPA) that modulate morphology and transfer ultraviolet (UV) photons into utilizable photoexcitations through an energy-transfer process in the active layer, thereby simultaneously enhancing device performance and suppressing photodegradation. In PM6: Y6 and PM6: L8-BO systems, the power conversion efficiencies (PCE) reach 16.1% and 17.5%, respectively, accompanied by markedly prolonged lifetimes under continuous UV illumination. Further analysis reveals that the structure of D-A-type additives substantially influences molecular packing and the associated energy-transfer pathways. The less self-aggregated UV326-DBOPA provides a superior efficiency and stability by enabling optimized intermolecular packing and intrinsic energy transfer within the photoactive layer. This work provides an integrated strategy for regulating morphology and harnessing UV energy, offering guidance for future additive molecular design.