Anti-solvent assisted multi-step deposition for efficient and stable carbon-based CsPbI2Br all-inorganic perovskite solar cell.

Abstract Inorganic halide perovskite CsPbI 2 Br has attracted tremendous attentions in the photovoltaic fields in view of its improved ambient phase stability and reasonable band gap (1.91eV). Traditional one-step solution-processed CsPbI 2 Br absorbers, however, usually suffer from poor morphology, low crystallinity and thin thickness, which impede further promotion of device performance. Herein, an anti-solvent assisted multi-step deposition strategy for high-quality CsPbI 2 Br film is demonstrated, wherein different anti-solvents are first introduced in the PbI 2 precursor filming processes to construct porous PbI 2 (DMSO) films. Then CsBr solution intercalates into the porous PbI 2 (DMSO) film by multi-step deposition, effectively facilitating the close contact of reactants and complete annealing reaction. CsBr drops and porosity degree of PbI 2 (DMSO) film are found to control the final morphology and phase composition of the perovskite film. Utilizing green ethanol (EtOH) treated PbI 2 film with high porosity and randomized orientation, highly pure-phase and full-coverage CsPbI 2 Br films with high thickness, large grain sizes and high crystallinity are obtained after optimizing CsBr drops. Finally, carbon-based all-inorganic planar perovskite solar cells (PSCs) with absorbers prepared through above methods achieve a champion efficiency of 10.21%, which is a record value for the CsPbI 2 Br PSCs without hole transport layer. More importantly, the unencapsulated all-inorganic CsPbI 2 Br device shows a promising long-term stability with no obvious efficiency degradation when exposed in ambient atmosphere with 15–30% relative humidity (RH) at room temperature for 44 days. Graphical abstract Image 1 Highlights • An anti-solvent assisted multi-step deposition strategy is developed to fabricate CsPbI 2 Br film. • Different anti-solvents are introduced to construct porous PbI 2 (DMSO) complex films. • Morphology and phase composition of film can be well controlled by adjusting CsBr dropping amount. • By optimizing CsBr deposition cycles and using EtOH anti-solvent, high-purity and thick CsPbI 2 Br film is obtained. • Carbon-based HTM-free CsPbI 2 Br planar PSCs achieve a champion efficiency of 10.21%. [ABSTRACT FROM AUTHOR]