High-performance and mechanically durable semi-transparent organic solar cells with highly transparent active layers

The flexibility and translucency aspects are unparalleled advantages of organic solar cells (OSCs), which have attracted great attention from the scientific and industrial communities. Currently, the key to improve the performance of flexible semi-transparent OSCs (ST-OSCs) lies in flexible transparent electrodes (FTEs) and the light-absorbing active layer. Herein, high-quality multi-layer FTEs with solar-weighted transmittance of 84.8% are employed, which allows the photo-active layer to effectively capture light and improve the light management in devices. In addition, multiple well-developed strategies, including alloy-like near-infrared acceptors (Y6:m-BTP-PhC6) and dilution of the donor with visible-range absorption (PM6), precisely utilize each band of photons, significantly balancing the conflict between photovoltaic and optical properties in ST-OSCs. The dilution of PM6 leads to highly transparent active layers with average visible transmittance of 39.3%, which is due to a decrease in donor absorption in the visible range and an increase in near-infrared absorption of the acceptor. As a result, high efficiencies of 16.44% and 11.48% are obtained for flexible opaque and semi-transparent cells. To the best of our knowledge, these results represent one of the best values for ST-OSCs based on flexible substrates. This work paves the path for realizing high-performance flexible ST-OSCs with excellent mechanical robustness, and contributes a major step toward practical applications.