Top and bottom electrode optimization enabled high-performance flexible and semi-transparent organic solar cells

The fabrication of highly efficient flexible and semitransparent large-area organic solar cells (OSCs) is an utmost requirement for the effective commercialization and industrialization of this technology. However, obtaining such large-area flexible devices with high transparency and high performance is a tremendous task. Herein, a series of high performing devices, with more than 8% power conversion efficiency (PCE) for large-area (1.25 cm2) flexible semitransparent OSCs have been successfully developed. The semitransparency has been maintained at around 16-24% average visible light transmittance (AVT), whereas even after 1000 bending cycles at a bending radius of 10 mm, the corresponding devices still maintained about 95% of their initial efficiency. This outstanding performance has been attributed to the rather unique top and bottom silver grid architecture. The bottom transparent flexible silver grid substrate (bottom electrode) produces the cavity effect with the top silver electrode, resulting in enhanced device performance with high transparency. Furthermore, the top metal electrode, which is composed of laser processed semitransparent charge-transporting busbars over the thin metal surface, guarantees efficient transmittance while enhancing the charge collection ability. Hence, such top busbar structures might be a general solution for overcoming the trade-off between the AVT and the PCE. Overall, this study provides a promising strategy for the transfer of large-area flexible semitransparent OSCs into practical industrial applications.