Chlorophyll Bilayer Heterojunction as a Hole-Transport Layer Enables Efficient and Stable Wide-Bandgap Perovskite Solar Cells

Abstract Wide-bandgap (WBG) perovskite solar cells (PSCs) are critically limited by nonradiative recombination losses that reduce their open-circuit voltage and power conversion efficiency (PCE). The hole-transport layer (HTL) plays a critical role in addressing this challenge. Herein, we report a chlorophyll (Chl) bilayer HTL composed of an electropolymerized nickel methyl 131-deoxo-pyropheophorbide-a bottom layer and a cyano-/hydroxyl-functionalized Chl-CN top layer. The two molecular layers form a bilayer heterojunction structure through strong π–π stacking, establishing hierarchical photocarrier transport channels that enable rapid interfacial hole extraction and efficient in-layer transport. Moreover, the cyano groups passivate Pb-related defects, relieve interfacial stress, and slow crystallization, while the hydroxyl groups suppress halide segregation through hydrogen bonding. These synergistic effects minimize nonradiative recombination channels for photogenerated carriers. Our 1.68 eV WBG PSCs incorporating this HTL achieve a high PCE of 23.51%. Unencapsulated devices retain over 90% of their initial PCE after 1000 h of maximum power point tracking under one-sun illumination. In addition, a four-terminal perovskite/silicon tandem cell incorporating this Chl heterojunction HTL achieves a PCE of 31.18%. This biobased bilayer interface design modulates photocarrier transport and suppresses nonradiative recombination, highlighting Chl derivatives for photon management in photovoltaics.