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.