Precise Nucleation Regulation and Defect Passivation for Highly Efficient and Stable Carbon-Based CsPbI2Br Perovskite Solar Cells

Carbon-based all-inorganic CsPbI2Br perovskite solar cells (C-PSCs) are regarded as a promising photovoltaic candidate due to their low cost, simple device structure, and high stability. However, their power conversion efficiency (PCE) is still too poor for commercial applications, mainly due to the lack of thick and high-quality CsPbI2Br films with less defects. In this work, three antisolvents are chosen to finely control the crystallization process of the CsPbI2Br film based on pure dimethyl sulfoxide solvent; a 500 nm-thick CsPbI2Br film is fabricated using isopropanol as an antisolvent. Furthermore, excess PbI2 is introduced to not only enhance the crystallinity of the CsPbI2Br film and passivate defects located at grain boundaries but also improve the hole extraction from the n-type CsPbI2Br film to the carbon electrode. Consequently, the PCE of CsPbI2Br C-PSC is dramatically boosted up to 12.78% with small hysteresis, which is among the highest values of all-inorganic C-PSCs. Moreover, the unencapsulated C-PSC demonstrates excellent long-term thermal stability, maintaining 93% of its initial PCE after aging at 85 °C for 600 h in dry air. Our work provides significant guidance for developing low-cost, high-performance, and stable CsPbI2Br C-PSCs.