Efficient and Stable All‐Inorganic CsPbIBr2 Perovskite Solar Cells Enabled by Dynamic Vacuum‐Assisted Low‐Temperature Engineering

Among all‐inorganic perovskite photoactive materials, CsPbIBr 2 demonstrates the most balanced trade‐off between optical bandgap and phase stability. However, the poor quality and high‐temperature engineering of CsPbIBr 2 film hinder the further optimization of derived perovskite solar cells (PSCs). Herein, a simple dynamic vacuum‐assisted low‐temperature engineering (merely 140 °C) is proposed to prepare high‐quality CsPbIBr 2 film (VALT‐CsPbIBr 2 film). Compared to HT‐CsPbIBr 2 film processed via conventionally high temperature (280 °C), VALT‐CsPbIBr 2 film presents higher crystallinity and more full coverage consisting of larger grains and fewer grain boundaries, which results in intensified light‐harvesting capability, reduced defects, and extended charge carrier lifetime. Benefiting from those improved merits, VALT‐CsPbIBr 2 PSCs show lower trap‐state densities, more proficient charge dynamics, and larger built‐in potential than HT‐CsPbIBr 2 PSCs. Consequently, VALT‐CsPbIBr 2 PSCs deliver a higher efficiency of 11.01% accompanied by a large open‐circuit voltage of 1.289 V and a remarkable fill factor of 75.31%, being highly impressive among those reported CsPbIBr 2 PSCs. By contrast, the efficiency of HT‐CsPbIBr 2 PSCs is only 9.00%. Moreover, VALT‐CsPbIBr 2 PSCs present stronger endurance against heat and moisture than HT‐CsPbIBr 2 PSCs. Herein, a feasible avenue to fabricate efficient yet stable all‐inorganic PSCs via low‐temperature engineering is provided.