Preparation And Investigation Of High-performence Perovskite Photodetectors Based On Magnesium Doped Hole Transport Layers

The photodetector is a device that converts incident optical signals into electrical signals.In recent years,as a new type of photovoltaic material,perovskites has been widely used in photodetectors of different structures,which contain a wide variety of and have excellent optoelectronic properties.In perovskite photodetectors,the interface defects between the perovskite light absorption layer and the transport layers will affect the extraction,transport and quenching of carriers.At the same time,the film-forming properties of the transport layer will also affect the properties of the film superimposed on it,thereby affecting the performance of the photodetectors.The performance of perovskite photodetectors can be enhanced by doping the transport layer,which can enhance charge transport,suppress carrier recombination,optimize energy level alignment,passivate interface defects and improve crystallinity of perovskite.In this study,organic lead halide perovskite CH₃NH₃PbI₃ and lead-free double perovskite Cs₂AgBiBr₆ are used as the light absorption layer of the photodetector,and nickel oxide is selected as the hole transport layer of the device.The experiment mainly studies the effects of doping magnesium in the hole transport layer on the interface properties of the light absorption layer and the performance of the device.The main research contents are discussed from two aspects:（1）The effects of Mg-doped NiO hole transport layers on the performance of CH₃NH₃PbI₃ self-driven photodetectors are investigated.The doping of Mg can increase the Ni vacancy in NiO films and the ratio of Ni³⁺/Ni²⁺,which will improve the hole mobility of NiO films.At the same time,the Mg-doped NiO films can promote the crystallization of the MAPbI₃ film,improve the interfacial contact performance,enhance the ability of hole transport layers to extract and transport charges,and inhibit carrier recombination.When the doping concentration of Mg is 1 mol%,the prepared photodetectors device have the best performance.Compared with the undoped device,its external quantum efficiency peak is increased from 80%to 88%,the detectivity is increased from1.7×10¹³ to 5.3×10¹³ Jones,and the responsivity is increased from 0.34 A?W^-1 to0.41 A?W^-1.（2）The effects of Mg-doped NiO hole transport layers on the performance of Cs₂AgBiBr₆ double perovskite photodetectors are investigated.The reported lead-free double perovskite films have poor quality,large band gaps and deep valence bands.There are few researches on matching its energy level with the energy levels of other functional layers.The energy level of NiO is adjusted by doping Mg to make it more matched with the energy level of Cs₂AgBiBr₆film,which can promote the extraction and transport of carriers,improve the quality of the film and the performance of the device.In this study,a P-I-N junction self-driven double perovskite photodetector is constructed using NiO,C₆₀ and Cs₂AgBiBr₆.The experimental results show that when the doping concentration of Mg is 3mol%,the prepared photodetectors have the best performance.Compared with the undoped device,the external quantum efficiency peak of Cs₂AgBiBr₆ photodetectors fabricated based on Mg-doped NiO increased from8.8%to 14.0%,the responsivity peak increased from 22 m A?W^-1 to 55 m A?W^-1the detectivity peak is raised from 1.0×10¹² Jones to 4.7×10¹² Jones.