Preparation And Performance Improvement Of Mapbbr₃/Si Self-powered Narrowband Photodetector

In recent years,organic-inorganic hybrid perovskite materials have attracted much attention due to their great success in photovoltaic devices.They have wide application prospects in optoelectronic devices such as solar cells,light-emitting diodes,and photodetectors because of their outstanding photoelectric properties such as high optical absorption coefficient,tunable direct bandgap,high carrier mobility,and long charge carrier diffusion length.In this thesis,we reported the preparation and performance improvement of the MAPbBr₃/Si heterojunction self-powered narrow-band photodetector.First of all,MAPbBr₃/Si heterojunction photodetector was prepared to realize self-powered narrow-band visible-light photodetection.Then aluminium oxide（Al₂O₃）thin films was inserted as the passivation interlayer,which further improved the performance of the photodetector.This paper mainly consists of the following parts:1.MAPbBr₃ microcrystals were grown on indium tin oxide（ITO）glass substrate by room-temperature anti-solvent assisted crystallization method.X-raying diffraction and scanning electron microscope results showed that as-grown MAPbBr₃microcrystals had high crystalline quality.MAPbBr₃ photodetector exhibited an on-off ratio of 280 at 1 V bias,a peak photo-responsivity of 1.21×10^-5 A/（W/cm²）,and rising/falling times of 99.8 ms and 101.9 ms,respectively.2.A self-powered narrow-band photodetector was prepared by growing MAPbBr₃microcrystals on the p-type silicon wafers.The results showed that the as-fabricated photodetectors operating under a bias voltage of 0 V exhibited high-performance photodetection including an open-circuit voltage of 0.88 V,a short-circuit current of1.42×10^-8 A,and a high on-off ratio of 5.3×10⁵.The photo-responsivity of the photodetector at 551 nm under 0 V bias reached 4.0×10^-4 A/（W/cm²）,and the full width at half maximum was only as narrow as 18.2 nm.The photo-generated carriers in the space charge region contribute to the photocurrent driven by the built-in electric field in MAPbBr₃/Si heterojunction,which results in the self-powered photodetection,and the MAPbBr₃ microcrystals can be functioned as an optical filter,which leads the narrow-band photodetection.3.Al₂O₃ thin films were grown by atomic layer deposition（ALD）as the passivation interlayer to fabricate a MAPbBr₃/Al₂O₃/Si heterojunction structure photodetector.Compared with the MAPbBr₃/Si device,the introduction of ALD-Al₂O₃ thin interlayer in the MAPbBr₃/Si heterojunctions reduced the dark current and increased the photocurrent simultaneously,therefore,the on-off ratio of the device under 0 V bias was as high as 2.2×10⁵,and the photo-responsivity reached 0.39 A/W.The passivation of Al₂O₃interlayer was demonstrated by the optical properties and water contact measurements.We concluded that the Al₂O₃ interlayer could passivate the interface trap states effectively,meanwhile holes can be transferred to Si substrate by tunneling through the Al₂O₃barrier,which further improve the photoelectric performance of the photodetector.