Fine‐Tuning Thickness‐Dependent Molecular Aggregation for Enhanced Performance in Semitransparent Organic Photovoltaics

Semitransparent organic photovoltaics (ST‐OPV) exhibit tremendous potential for application in integrated photovoltaic architecture. The reduction of the ratio of wide‐bandgap donors in the active layer is crucial for enhancing both the power conversion efficiency (PCE) and the average visible light transmittance (AVT), which are key performance indicators for ST‐OPV. Herein, successful suppression of the thickness‐dependent transition from H‐aggregates to J‐aggregates in PM6 films was achieved through temperature control, significantly improving charge transport and extraction efficiency, thereby markedly enhancing the PCE of sequential processed pseudo p‐i‐n devices employing the Y6 acceptor. With ≈30% AVT maintained, the PCE increases from 6.50% to 11.10%, while the light utilization efficiency rises from 1.98% to 3.40%. Unlike previous studies primarily focused on optical coupling structure design, this research underscores the precise control of molecular aggregation behavior in the active layer material, demonstrating the innovativeness of material and structural design and offering new avenues and methodologies for the development of future semitransparent photovoltaic materials.