Combination of highly photovoltaic and highly transparent materials enables record performance semitransparent organic solar cells

Semitransparent organic solar cells (ST-OSCs) are an important branch of organic solar cells, which have considerable application prospects in building photovoltaic, smart greenhouses, and clean energy vehicle skylights. However, a compromise between the power conversion efficiency (PCE) and the average visible transmittance (AVT) has been the obstacle in the field of ST-OSCs. Therefore, comprehensive consideration of PCE, AVT and the resulting light utilization efficiency (LUE), is very necessary to objectively evaluate the performance of a ST-OSC device. Herein, we report a facile strategy by combination of the advantages of the highly photovoltaic materials with highly transparent materials to construct high performance ternary active layer for ST-OSCs. Two ternary systems PM6:PCE10-2F:Y6 and PCE10-2F:PM6:Y6 are developed according to their host binary blends PM6:Y6 (w:w = 1:1.2) and PCE10-2F:Y6 (w:w = 1:2.5) respectively. The PCEs of the opaque and transparent devices are observed to be both improved in the ternary systems relative to their corresponding host systems, due to the complementary absorption, optimized morphology and charge dynamics. More importantly, combination of highly photovoltaic materials with highly transparent materials enables a well-balanced PCE and AVT, leading to significantly enhanced LUE. For PM6:PCE10-2F:Y6 devices, simultaneously improved PCE and AVT are obtained. Intriguingly, ST-OSC based on PCE10-2F:PM6:Y6 achieves an impressive PCE of 12.25 % and a high AVT of 36.57 %, which is the highest efficiency for the AVT over 30 %. A maximum LUE of 4.48 % is also a breakthrough of the ST-OSCs without complex photo-coupling layers. These findings demonstrate that combination of the high PCE system with high AVT system is a promising strategy for developing high performance ST-OSCs.