Unravelling the Role of Indium in Enhancing the Stability of Mixed Tin–Lead Perovskite Solar Cells

Tin–lead metal halide perovskites show promise as light-absorbing materials with a tunable band gap (1.2–1.4 eV) for efficient perovskite solar cells (PSCs) with less toxicity. However, the instability of the tin(II) ionic state limits the lifetime of their PSCs, which reduces their real-world feasibility. Herein, indium(III) iodide (InI₃) is used to modulate the Sn–Pb perovskite crystal lattice to improve the stability of the film, in addition to improving the photovoltaic performance of the corresponding PSC devices. It is found that the indium cation shows an ability to substitute tin(II) vacancies in the perovskite crystal structure, resulting in a more stable structure. The InI₃-modified films exhibit enhanced surface morphology and crystallinity, reduced trap state density, and nonradiative recombination in the solar cells expressed in improved device performance of the Sn–Pb-based PSCs from 17.2 to 18.1% and an enhancement in the stability of the perovskite during exposure to elevated temperature and humid atmospheric air.