Research On Photovoltaic Ultraviolet-blue Photodetector Based On Lead-free Double Perovskite Cs₂AgBiBr₆

Recently,the new perovskite materials have attracted much attention and shown wide application prospects in the fields of new solar cells,light-emitting diodes and photodetectors,due to their excellent physical properties such as strong light absorption capacity,low exciton binding energy,bipolar carrier transport characteristics,long carrier lifetime and so on.However,hybrid organic-inorganic perovskite materials（HOPs）and organic small molecules are usually used as optical absorption materials and carrier transport materials in perovskite-based photodetectors,which resulting device instability and lead toxicity seriously and hindering the process of real application of perovskite devices.Aiming at the above problems,inorganic lead-free double perovskite materials Cs₂AgBiBr₆ were prepared by one-step spin coating method,and photovoltaic ultraviolet-blue photodetector was constructed on this basis,and the excellent device performance was obtained.The following main results were obtained:（1）Preparation and optimization of high-quality double perovskite Cs₂AgBiBr₆film.Using n-type GaN/Sapphire wafer as substrate,a simple one-step solution method was used to grow inorganic lead-free double perovskite Cs₂AgBiBr₆ films.The effect of annealing temperature on films quality and stability was systematically studied,and the optical and electrical properties of the films were measured.The optimized preparation conditions of the double perovskite Cs₂AgBiBr₆ film with excellent optical properties,excellent electrical properties and good stability have been obtained.（2）Preparation and optimization of p-type NiO film of device hole transport layer.The p-NiO films with good optical and electrical properties were successfully prepared by magnetron sputtering with high quality using Cs₂AgBiBr₆/n-GaN/Sapphire as substrate.The resistivity of the film prepared under the optimized conditions is as low as 7.419Ωcm,and the carrier concentration is as high as 4.17×10¹⁸ cm^-3,which can well meet the basic electrical performance requirements of the hole transport layer.（3）Construction and performance test of photovoltaic ultraviolet-blue photodetectors.Taking n-GaN film as electron transport layer,double perovskite Cs₂AgBiBr₆ film as intrinsic layer,p-NiO film as hole transport layer and In and Au as upper and lower electrodes,photovoltaic photodetectors with Au/p-NiO/Cs₂AgBiBr₆/n-GaN/In heterostructures were prepared.The test results show that the dark current of the device is 1.89×10^-9 A with an UV-blue wide spectral response range.Under 365 nm ultraviolet light with a zero bias of 2.70 m W cm^-2,device showed a switching ratio of 1.16×10³,a light response of 33 m A W^-1,a specific detecivity of3.28×10¹¹ Jones.The periods of rise and fall time were 151μs and 215μs,respectively.And the device has good thermal stability and air stability.The research results of this thesis provide a new idea for the preparation of environmentally friendly,self-powered,and stable device performance broad-spectrum perovskite photodetectors.