Unconventional solution-phase epitaxial growth of organic-inorganic hybrid perovskite nanocrystals on metal sulfide nanosheets

Epitaxial heterostructures based on organic-inorganic hybrid perovskites and two-dimensional materials hold great promises in optoelectronics, but they have been prepared only via solid-state methods that restricted their practical applications. Herein, we report cubic-phased MAPbBr₃ (MA=CH₃NH₃ ⁺) nanocrystals were epitaxially deposited on trigonal/hexagonal-phased MoS₂ nanosheets in solution by facilely tuning the solvation conditions. In spite of the mismatched lattice symmetry between the square MAPbBr₃ (001) overlayer and the hexagonal MoS₂ (001) substrate, two different aligning directions with lattice mismatch of as small as 1% were observed based on the domainmatching epitaxy. This was realized most likely due to the flexible nature and absence of surface dangling bonds of MoS₂ nanosheets. The formation of the epitaxial interface affords an effective energy transfer from MAPbBr₃ to MoS₂, and as a result, paper-based photodetectors facilely fabricated from these solution-dispersible heterostructures showed better performance compared to those based on MoS₂ or MAPbBr₃ alone. In addition to the improved energy transfer and light adsorption, the use of MoS₂ nanosheets provided flexible and continuous substrates to connect the otherwise discrete MAPbBr₃ nanocrystals and achieved the better film forming ability. Our work suggests that the scalable preparation of heterostructures based on organic-inorganic hybrid perovskites and 2D materials via solution-phase epitaxy may bring about more opportunities for expanding their optoelectronic applications.