Indium-Doped CsPbI_2.5Br_0.5 with a Tunable Band Structure and Improved Crystallinity for Thermo-Stable All-Inorganic Perovskite Solar Cells

Hybrid organic–inorganic halide perovskite solar cells (PSCs) have garnered significant attention in the field of photovoltaics. Despite the rapid advancements in photoelectric conversion efficiency (PCE), the sensitivity of hybrid perovskites to moisture and heat poses challenges to device stability. All-inorganic PSCs (AIPSCs) eliminate the use of traditional organic components, resulting in significantly extended operational lifetimes. Herein, we report the doping of indium bromide (InBr 3 ) into the lattice of CsPbI 2.5 Br 0.5 -based all-inorganic perovskites, leading to large crystalline grain sizes and tunable energy band levels by adjusting the concentration of InBr 3 dopants. AIPSCs based on highly stable In-doped CsPbI 2.5 Br 0.5 absorber layers can be conveniently fabricated in an ambient air environment. Moreover, screen-printable nanocarbon counter electrodes with high stability and low cost are introduced to replace unstable organic hole-transport materials and expensive noble metal electrodes, thus further increasing ambient stability and greatly reducing device costs. As a result, the In-doped CsPbI 2.5 Br 0.5 -based AIPSCs achieve a champion PCE of 12.05% and favorable heat endurance with a PCE retention of 80% after being continuously heated at 100 °C for over 1632 h. This work provides a feasible strategy of lattice doping to tackle the intractable issue regarding the intrinsic thermal instability of inorganic perovskite materials for fabricating AIPSCs with a wide absorption range and high environmental stability.