Natural binders for synchronous management of iodine species adsorption and redox toward sustainable carbon-based perovskite solar cells

Abstract

Under illumination or heat conditions, iodine ions in perovskites are highly susceptible to oxidation into iodine molecules (I⁰). This can set off a chain reaction that accelerates perovskite degradation and has a major negative influence on the stability of halide perovskite solar cells. Herein, a strategy for the simultaneous management of iodine species through adsorption and redox was proposed for sustainable carbon-based perovskite solar cells (C-PSCs). A double-helix structure of chitosan was incorporated as an interlayer at the buried interface to capture I⁰. It has been found that chitosan can capture I⁰ in its double-helix structure, effectively preventing the degradation of perovskite film. Additionally, the introduction of acacia gum to the precursor solution shows its redox effect with I⁰. The results demonstrate that the champion power conversion efficiency (PCE) of 19.53% has been achieved for the hole transport layer-free C-PSCs. The non-encapsulated devices exhibit excellent thermal stability, maintaining 95.6% of their initial PCE after storage for 1080 h according to the ISOS-D-1 protocol. Meanwhile, after 240 h of storage according to the ISOS-D-2 protocol, they retain 84.1% of their initial PCE. The work offers a fresh approach to iodine management based on the synchronous effect of physical and chemical interaction.