Surface reconstruction strategy improves the all-inorganic CsPbIBr2 based perovskite solar cells and photodetectors performance

Inorganic cesium lead halides have triggered the widespread interest of scientist researchers because of their distinct advantages. CsPbIBr2 is an excellent optoelectronic material which can well balance the stability and the photoelectric conversion efficiency of the device. However, the large energy loss (E-loss) is the most urgent challenge which needs to be solved. Here, a simple method is presented to reduce E-loss and improve the open-circuit voltage (V-oc) of the CsPbIBr2 PSCs through effective surface reconstruction with formamidinium iodide (FAI). The treatment not only induces a halide exchange at the interface, but also changes the surface termination of CsPbIBr2. As a result, the disorder of the lattice structure has been suppressed and the lattice constant has been enlarged, leading to better stability and reduced bandgap. Moreover, the treatment optimizes the film morphology, adjusts the energy level, accelerates the carrier transport and further suppresses nonradiative recombination. Finally, the energy loss is restrained and the device realizes a record high efficiency of 11.31% with a high V-oc of 1.34 V. Besides, the treated devices also present high sensitivity, responsivity and detectivity in the photodetector applications. Furthermore, the devices exhibit excellent stability under continuous heating, continuous illumination and long-term ambient stored conditions.