One-Step Gas–Solid-Phase Diffusion-Induced Elemental Reaction for Bandgap-Tunable CuaAgm1Bim2In/CuI Thin Film Solar Cells
Erchuang Fan, Manying Liu, Kangni Yang, Siyu Jiang, Bingxin Li, Dandan Zhao, Yanru Guo, Yange Zhang, Peng Zhang, Chuantian Zuo, Liming Ding, Zhi Zheng
Abstract
Abstract Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness, high element abundance, and low cost. Here, we developed a strategy of one-step gas–solid-phase diffusion-induced reaction to fabricate a series of bandgap-tunable Cu a Ag m1 Bi m2 I n /CuI bilayer films due to the atomic diffusion effect for the first time. By designing and regulating the sputtered Cu/Ag/Bi metal film thickness, the bandgap of Cu a Ag m1 Bi m2 I n could be reduced from 2.06 to 1.78 eV. Solar cells with the structure of FTO/TiO 2 /Cu a Ag m1 Bi m2 I n /CuI/carbon were constructed, yielding a champion power conversion efficiency of 2.76%, which is the highest reported for this class of materials owing to the bandgap reduction and the peculiar bilayer structure. The current work provides a practical path for developing the next generation of efficient, stable, and environmentally friendly photovoltaic materials.