Suppressed Oxidation and Photodarkening of Hybrid Tin Iodide Perovskite Achieved with Reductive Organic Small Molecule

Tin­(II)-based halide perovskites have shown promise in lead-free and mixed tin­(II)–lead ideal-band-gap photovoltaic applications. Nonetheless, they notoriously suffer from oxidation in oxygen environments, thereby sustaining rapid self-doping during synthesis and further material degradation in postfabrication stages. As such, enhancing the chemical stabilities of tin­(II) halide perovskites is imperatively crucial for the further advancement of any relevant eco-friendly and low-band-gap photovoltaic technology. Here, we demonstrate that hydroquinone, a chemically reductive organic molecule, can effectively improve the stability of perovskite methylammonium tin­(II) iodide (CH₃NH₃SnI₃) in a dry air environment, as shown by X-ray diffraction and X-ray photoelectron spectroscopic studies. Furthermore, the luminescence longevity of the hydroquinone-treated CH₃NH₃SnI₃ film is much greater than its undoped pristine counterpart in ambient air, as unambiguously evidenced by their time-dependent steady-state photoluminescence spectra. Meanwhile, time-resolved photoluminescence (TR-PL) decays reveal nearly unchanged carrier recombination lifetimes in both types of perovskite materials during degradation, which therefore infers a facile oxidation process for these thin films. This work provides a practical clue to stable and high-performance tin­(II)-based perovskite optoelectronics.