Flux-mediated growth strategy enables low-temperature fabrication of high-efficiency all-inorganic CsPbIBr2 perovskite solar cells

Flux-mediated crystal growth strategy is highlighted by its feasibility of low-temperature, fast growth of high-quality metal oxides, as a result of enhanced diffusion of reactants. Herein, this strategy is successfully extended for CsPbIBr2 film for the first time by simply incorporating a certain amount of CH3NH3Br into the precursor film. The CH3NH3Br species served as flux agents could dramatically boost the growth and coarsening of CsPbIBr2 grains. Hence, a dense and uniform CsPbIBr2 film consisted of micro-sized and high-crystallinity grains is attained at a low temperature of 200 °C. This processing temperature is lowered by one-third in contrast to the previous methods. More importantly, the carbon-based, all-inorganic perovskite solar cell (PSC) based on such desired CsPbIBr2 film yields an optimized efficiency of 10.82%, which stands a record-high value for CsPbIBr2-based PSCs without configuration modifications. Meanwhile, the PSC delivers excellent operation stability under light, thermal, and humidity stresses. Consequently, the work contributes to establish a facile approach to low-temperature preparation of high-quality CsPbIBr2 film for development of practical and efficient PSCs.