Epitaxial Growth of CsPbBr Pyramids/CdS Nanobelt Heterostructures for High-Performance Photodetectors.

Perovskites have great potential for optoelectronic applications due to their high photoluminescence quantum yield, large absorption coefficient, great defect tolerance, and adjustable band gap. Perovskite heterostructures may further enhance the performance of optoelectronic devices. So far, however, most of perovskite heterostructures are fabricated by mechanical stacking or spin coating, which could introduce a large number of defects or impurities at the heterointerface owing to the random stacking process. Herein, we report the epitaxial growth of CsPbBr pyramids/CdS nanobelt heterostructures via a 2-step vapor deposition route. The CsPbBr triangular pyramids are well aligned on the surface of CdS nanobelts with the epitaxial relationships of (0-22)||(1-20) and (-211)||(002). Time-resolved photoluminescence results reveal that effective charge transfer occurred at the heterointerface, which can be attributed to the type-II band arrangement. Theoretical simulations reveal that the unique CsPbBr pyramids/CdS nanobelt structure facilitates diminishing the reflection losses and enhancing the light absorption. The photodetector based on these CsPbBr pyramids/CdS nanobelt heterostructures exhibited an ultrahigh photoswitching ratio of 2.14 × 10, a high responsivity up to 4.07 × 10 A/W, a high detectivity reaching 1.36 × 10 Jones, fast photoresponses (τ = 472 μs and τ = 894 μs), low dark current, and suppressed hysteresis.