Ionic Liquid-Induced Ostwald Ripening Effect for Efficient and Stable Tin-Based Perovskite Solar Cells

Tin-based perovskite solar cells (PVSCs) are regarded as the most promising alternative among lead-free PVSCs. However, the rapid crystallization for tin-based perovskite tends to cause inferior film morphology and abundant defect states, which make poor photovoltaic performance. Here, 1-butyl-3-methylimidazolium bromide (BMIBr) ionic liquids (ILs) with strong polarity and a low melting point are first employed to produce the Ostwald ripening effect and obtain high-quality tin-based perovskite films with a large grain size. Meanwhile, the non-radiative recombination ascribed from defect states can also be effectively reduced for BMIBr-treated perovskite films. Consequently, a photoelectric conversion efficiency (PCE) of 10.09% for inverted tin-based PVSCs is attained by the Ostwald ripening effect. Moreover, the unencapsulated devices with BMIBr retain near 85% of the original PCE in a N-2 glovebox beyond 1200 h and about 40% of the original PCE after exposure to air for 48 h.

Automated summary

By employing 1-butyl-3-methylimidazolium bromide (BMIBr) ionic liquids, the Ostwald ripening effect was successfully achieved to produce high-quality tin-based perovskite films with large grain size, leading to improved photovoltaic performance. The use of BMIBr also effectively reduced non-radiative recombination in the perovskite films, resulting in a photoelectric conversion efficiency (PCE) of 10.09% for inverted tin-based PVSCs. Furthermore, the unencapsulated devices treated with BMIBr showed excellent stability with nearly 85% of the original PCE retained after 1200 hours in a N-2 glovebox.