Efficient Semitransparent Organic Solar Modules with Exceptional Diurnal Stability Through Asymmetric Interaction Induced by Symmetric Molecular Structure

The symmetry-breaking design strategy of nonfullerene acceptor can improve the performance of semitransparent organic solar cells (ST-OSCs). However, no report exists on the "asymmetric molecular interaction" induced by symmetric molecular structure in nonfullerene acceptors. Herein, we showcase that 2D fluorophenyl outer groups in symmetric 4FY promote dipole-driven self-assembly through asymmetric molecular interactions, resulting in a tighter packed structure than Y6 with the same symmetric geometry. Such unique properties lead to high-performance layer-by-layer OSCs, accompanied by simultaneously reduced energy and recombination losses and improved charge-related characteristics. ST-OSCs based on PCE10-2F/4FY achieve notable power conversion efficiency (PCE) of 10.81%, average visible transmittance of 45.43%, and light utilization efficiency (LUE) of 4.91%. Moreover, exceptional diurnal cycling stability is observed in the ST-OSCs based on PCE10-2F/4FY with much prolonged T₈₀ up to 134 h, which is about 17 times greater than the reference PCE10-2F/Y6. Lastly, we fabricate highly efficient semitransparent organic solar modules based on PCE10-2F/4FY (active area of 18 cm²), which shows PCE of 6.78% and the highest LUE of 3.10% to date for all-narrow bandgap semitransparent organic solar modules. This work demonstrates that asymmetry-driven molecular interactions can be leveraged to fabricate large-area ST-OSCs that are efficient and stable under realistic operating conditions.