Improved Fluorescence and Photoelectrical Properties of CsPbBr₃ by Constructing Heterojunctions under Pressure

All-inorganic cesium lead bromide quantum dots (CsPbBr₃ -QD) compounds are potential candidates for optoelectronic devices, because of their excellent fluorescence luminescence and thermal stability. However, the many heterojunction interfaces and large band gap induce the low power conversion efficiency in the CsPbBr₃ -QD heterojunction, limiting its practical applications. Hereby, in combination with the pressure regulation and TiO₂ /CsPbBr₃ -QD heterojunction, the interface interaction within the heterojunction can be enhanced and the band gap can be narrowed. The pressure-induced O─Ti─O bond softening and PbBr₆ octahedron stiffening at the interface region significantly enhance the interface interactions that are favorable to the carrier transport. Compared with CsPbBr₃ -QD, the atomic interaction between Pb and Br of TiO₂ /CsPbBr₃ -QD heterojunction can be dramatically enhanced at high pressures, leading to increased band gap narrowing rate by two times, which is useful to widen the absorption spectrum. The fluorescence intensity increases by two times. Compression increases the photocurrent and maintains it after the pressure is released, which is due to the enhanced interface interaction induced by the high pressure. The findings provide new opportunities to adjust the physical properties of perovskite heterogeneous structures, and have important applications in the field of new-generation photovoltaic devices.