Edge assisted epitaxy of CsPbBr₃ nanoplates on Bi₂O₂Se nanosheets for enhanced photoresponse

Bi_2O_2Se has been proved to be a promising candidate for electronic and optoelectronic devices due to their unique physical properties. However, it is still a great challenge to construct the heterostructures with direct epitaxy of hetero semiconductor materials on Bi_2O_2Se nanosheets. Here, a two-step chemical vapor deposition (CVD) route was used to directly grow the CsPbBr_3 nanoplate-Bi_2O_2Se nanosheet heterostructures. The CsPbBr_3 nanoplates were selectively grown on the Bi_2O_2Se nanosheet along the edges, where the dangling bonds provide the nucleation sites. The epitaxial relationships between CsPbBr_3 and Bi_2O_2Se were determined as 200_\rm Bi_2O_2Se||110_\rm CsPbBr_3 and 110_\rm Bi_2O_2Se||200_\rm CsPbBr_3 by transmission electron microscopy characterization. The photoluminescence (PL) results reveal that the formation of heterostructures results in the remarkable PL quenching due to the type-I band arrangement at CsPbBr_3/Bi_2O_2Se interface, which was confirmed by ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe measurements, and makes the photogenerated carriers transfer from CsPbBr_3 to Bi_2O_2Se. Importantly, the photodetectors based on the heterostructures exhibit a 4-time increase in the responsivity compared to those based on the pristine Bi_2O_2Se sheets, and the fast rise and decay time in microsecond. These results indicate that the direct epitaxy of the CsPbBr_3 plates on the Bi_2O_2Se sheet may improve the optoelectronic performance of Bi_2O_2Se based devices.