Hierarchical Dual-Scaffolds Enhance Charge Separation and Collection for High Efficiency Semitransparent Perovskite Solar Cells

Organometal halide perovskite solar cells (PSCs) have shown much promise to be made semitransparent (ST) for a variety of applications. However, charge separation and collection are still inefficient from the ultrathin absorber layer and thus limit the ST-PSCs performance. Herein a type of hierarchical dual scaffolds is first reported to tackle this problem consisting of a quasi-mesoscopic inorganic (TiO₂) layer and a percolating organic (phenyl-C61-butyric acid methyl ester) manifold throughout the capped or filled perovskite bulk. It is demonstrated that the soft PCBM scaffold affords efficient charge separation due to the formation of a penetrating network intimately interfaced with perovskite crystals, meanwhile the quasi-mesoporous hard TiO₂ scaffold strongly based on the substrate further offers a continuous electron transport. As a result, the ST-PSCs based on the ultrathin perovskite layer (≈100 nm) with the dual-scaffolds have achieved an internal quantum efficiency of ≈100%, boosting the device efficiency to 12.32%. Furthermore, the real ST-PSCs fabricated by replacing the Ag electrode with a PEDOT:PSS transparent electrode have reached an efficiency of 8.21% with an average visible transmittance of 23%, placing among the highest performing devices of the kind reported to date.