Efficient CsSnI3-based inorganic perovskite solar cells based on a mesoscopic metal oxide framework via incorporating a donor element

Abstract

A successful application of perovskite solar cells (PSCs) must face socioeconomic challenges such as lead poisoning. In this regard, Sn-based halide perovskite compounds, such as CsSnI₃, have attracted tremendous attention as effective replacements to their counterparts. However, the current CsSnI₃ PSCs are still plagued with the tough issues of low efficiency and chemical instability. Herein, for the first time, we present a chemical doping agent, namely, cobaltocene (denoted CoCp₂) with a strong electron-donating ability as a stabilizer and an electrical property manipulator of the inorganic CsSnI₃ perovskite for photovoltaic applications. A thermal-driven electron injection from CoCp₂ into CsSnI₃ maintains a reducing environment and thereby effectively suppresses Sn²⁺ oxidation (named after remote reduction), which can be confirmed by an increase in the density of states near the Fermi level and the emergence of the oxidized species, cobaltocenium (CoCp₂⁺). Therefore, we have achieved an unprecedented efficiency of 3.0% under standard illumination test conditions in air for a perovskite solar cell using a mesoporous TiO₂/Al₂O₃/NiO/carbon framework. We further noticed that without the remote reduction treatment, such devices produced negligible photovoltage and photocurrent. The incorporation of donor elements offers a novel and viable strategy to develop stable Sn-based inorganic PSCs with attractive properties for practical applications.