Light/heating/humidity induced reversible transformation between CsPb2Br5 and CsPbBr3 for switchable photoluminescence and heterostructure diodes

CsPb 2 Br 5 has attracted a tremendous attention recently owing to its high stability and unusual optical properties. However, the transformation between CsPb 2 Br 5 and CsPbBr 3 has yet been fully understood and the origin of the bright green emission in CsPb 2 Br 5 is still under debate . In this work, we elucidate the mechanism of the abnormal green emission in CsPb 2 Br 5 and reveal the light/heating/humidity induced reversible transformation between CsPb 2 Br 5 and CsPbBr 3 . The detailed structure characterization indicates the successful synthesis of pure phase CsPb 2 Br 5 , which exhibits a non-luminous feature. Remarkably, after the treatment of ultraviolet laser irradiation or annealing, the pure phase CsPb 2 Br 5 can be transformed partially or completely into CsPbBr 3 , yielding an unexpected bright green emission. In addition, the transformed CsPbBr 3 can be converted back to CsPb 2 Br 5 under the humidity environment, demonstrating the reversible transformation and photoluminescence switch. Interestingly, CsPbBr 3 derived from transformed CsPb 2 Br 5 exhibits superior emission properties such as higher photoluminescence stability, compared with the one-spot directly synthesized CsPbBr 3 . Moreover, the light induced transformation facilitates the fabrication of CsPb 2 Br 5 /CsPbBr 3 nano-heterostructure diodes with a high rectification ratio. These results provide an important insight into the photophysics and transformation mechanism of all-inorganic Cs-Pb-Br perovskites for photonics/electronics device applications.