Waveguide Photodetector Based on Perovskite Single-Crystal Heterojunction

Perovskite single-crystal sheet (SCS) lateral-structured photodetector typically needs to guide the signal light in free space to the SCS surface for photoelectric conversion to realize photodetection. However, the device performance in this working mode is highly dependent on the surface state of the active layer. To overcome this potential issue, this study puts forward a strategy of MAPbBr(3)-MAPbI(3) SCS heterojunction waveguide (HWG), in which MAPbBr(3) SCS is utilized as the waveguide (WG) structure to couple the far-field signal light into the confined near-field and propagates it to the active layer as a planar WG, directly exciting the internal single-crystal lattices of MAPbI(3) SCS, without taking into account the surface state. The device performance loss rate is 6 dB/mm, and its optimal performance can be increased by 60 times compared to that when light is guided to surface mode. Additionally, based on the visible light transparency and water insolubility of PbBr2, this study also verified the feasibility of PbBr2-MAPbI(3) HWG devices. Despite the suboptimal structural geometry of the PbBr2 wire cluster leading to an increased loss rate of 11.3 dB/mm, the device encapsulated with silicone sealant demonstrates considerable stability, with the performance decaying by only 7% after being immersed in the water for 100 h. The findings of this study suggest that the constructed SCS-HWG configuration provides a feasible architecture for high-performance SCS photodetectors.