Fabrication And Photoelectric Properties Of All-Inorganic Lead Halide Perovskite/Two-Dimensional Heterojunctions

All-inorganic lead halide perovskite CsPbBr₃has become an attractive high-performance material for photodetectors due to its low preparation cost,strong optical absorption capacity and high external quantum efficiency.Compared with nanomembranes with low charge separation efficiency due to quantum limited effect,CsPbBr₃microcrystals have lower trap density,longer carrier diffusion length,and excellent photoelectric conversion performance.However,the low carrier mobility of CsPbBr₃perovskite hinders its wide practical application.Therefore,two-dimensional materials with high carrier mobility and all-inorganic lead halide perovskite can be selected to construct heterojunctions based on the heterojunction to make up for the deficiency of the performance of a single material,so as to improve the performance of CsPbBr₃photodetectors.Herein,CsPbBr₃microcrystals and MoS₂two-dimensional materials were successfully prepared by chemical vapor deposition method,which is not easy to introduce impurities and can be mass-produced,and CsPbBr₃/MoS₂/IDT and CsPbBr₃/MoO₃/ITO heterojunction photodetectors were constructed,and the photoelectric properties and photoresponsivity of materials and devices were studied.The main contents are as follows:（1）CsPbBr₃microcrystals with large area,compact uniformity and high crystallinity were grown in situ by simple and efficient CVD method.By optimizing the fabrication temperature of CsPbBr₃microcrystals,it was concluded that:When the growth temperature is 330℃,CsPbBr₃luminous performance is optimal,the strongest light response,maximum photocurrent at 3 V bias of up to 84μA.（2）Coupling two-dimensional MoS₂materials with CsPbBr₃microcrystals by CVD method demonstrates a heterojunction interface engineering designed to improve the photoelectric properties of CsPbBr₃photodetectors.The MoS₂carrier extraction layer is conducive to electron injection,and the large injection barrier of the CsPbBr₃/MoS₂heterojunction depletion layer restricts the hole to the perovskite layer,resulting in the effective separation of photogenerated carriers at the heterojunction interface.The photoluminescence quenching and lifetime shortening of the heterojunction further prove that there is a large amount of charge transfer between the interface of CsPbBr₃and MoS₂.The results show that the photodetector based on CsPbBr₃/MoS₂/IDT heterojunction has high optical responsiveness(23.4 A W^-1),excellent detection rate(1.48×10¹³Jones)and switching ratio（1.35×10⁵）.These are all an order of magnitude better than pure CsPbBr₃photodetectors(1.92A W^-1,2.47×10¹²Jones),and heterojunction photodetectors have a shorter response time（0.07ms）.（3）A large area of MoO₃thin film was successfully prepared by atomic layer deposition,and it was combined with CsPbBr₃microcrystals to construct heterojunction photodetectors.The Cs Pb Br3/Mo O3/ITO heterojunction photodetector has excellent photoelectric properties and high optical detection capability.The photoresponsivity can reach 37.209 A W-1,the detectivity is 1.64×1012 Jones,and the rise and fall times are 0.06 and 0.04 ms,respectively,at 3 V bias voltage.Compared with pure Cs Pb Br3 perovskite devices,the responsivity of heterojunction photodetectors is improved by 3.54 times.Cs Pb Br3 acts as an optical absorbing layer,absorbing photons and releasing electrons.The introduction of Mo O3 promotes the separation and transport of heterojunction photocarriers and improves the optical response performance of the device.In this study,high performance all-inorganic perovskite heterostructures were grown in situ by CVD,which provided a basis for the large-scale production of perovskite photodetectors.