Precise stress control of inorganic perovskite films for carbon-based solar cells with an ultrahigh voltage of 1.622 V

All-inorganic cesium lead bromide (CsPbBr3) perovskite solar cell is one promising candidate to balance high efficiency and poor stability of organic-inorganic hybrid photovoltaics. The charge carrier transport can be maximized for high-efficiency devices through precise stress control during perovskite grain growth process to obtain high-quality full-bromine CsPbBr3 halide films. We present here the monolayer-aligned and large-grained CsPbBr3 perovskite films through precise control of crystallization temperature of PbBr2 film because the lattice volume is enlarged by 2.18 times during the phase conversion from PbBr2 to CsPbBr3, which helps to minimize residual-stress-induced grain boundaries and defect-induced charge recombination. Upon further interfacial modification by nitrogen doped carbon quantum dots, the hole transporting materials free, all-inorganic CsPbBr3 perovskite solar cell achieves a champion efficiency as high as 10.71% with an ultrahigh open-circuit voltage of 1.622 V. Moreover, the unencapsulated solar cell demonstrates remarkable long-term stability in 85% humidity in air atmosphere.