Preparation And Performance Of Cs₂AgBiBr_6-xCl_x Single Crystal Photodetector Based On Doping Compensation

In recent years,perovskite materials have been widely used in various optoelectronic devices due to their excellent photoelectric properties such as adjustable band gap,high optical absorption coefficient,long carrier lifetime,long carrier diffusion length and high carrier mobility.However,most of the current perovskite materials have toxic lead as their core component,and the organic components in organic-inorganic hybrid perovskites lead to poor environmental stability,which is detrimental to their large-scale commercial development.In order to better solve these issues,all inorganic lead-free double perovskite materials have been widely concerned by researchers for their advantages such as low physiological toxicity,high environmental stability,large atomic number,and easy crystallization growth from solution.However,inversion defects are easily to be introduced in preparation process of the double perovskite materials,resulting in high trap state density,which is unfavorable for the separation and extraction of photo-generated carriers,thus limiting the performance of devices based on the double perovskite materials.Therefore,in this work,Cl ions doping compensation Cs₂AgBi Br_6-xCl_xsingle crystals（SCs）with low trap state density were prepared by rational doping compensation strategy,further,photodetector and X-ray detector based on Cs₂AgBi Br_6-xCl_xSCs were constructed,and their detection performance were discussed.The main research work is as follows:1.The dopant-compensated double perovskite Cs₂AgBi Br_6-xCl_xSCs（Cl doping ratio:1.12%）with an average size of 3×3×2 mm³and low trap state density were grown by low-temperature solution crystallization method.Among them,the doped Cs₂AgBi Br_5.933Cl_0.067SCs show higher crystal quality than the other sample SCs.The surface of the Cs₂AgBi Br_5.933Cl_0.067SCs are smooth,flat,and without holes.The root mean square roughness（Rq）of 0.495 nm,a trap state density of 3.84×10⁹cm^-3,the mobility is 129 cm²V^-1s^-1and the product ofμτis 1.16×10^-3cm²V^-1.2.Gold（Au）as electrodes,based on Cs₂AgBi Br_5.933Cl_0.067SCs(constructed the metal-semiconductor-metal（MSM）planarsymmetricdetectors(Au/Cs₂AgBi Br_5.933Cl_0.067/Au),which has achieved good performance in both optical detection and X-ray detection.Under 5 V bias,the peak responsivity of the device is60.8 m A/W at 530 nm.I-V characteristic shows that the device has a switching ratio of2.7×10³,and I-t characteristic shows that the device has good cycle stability and repeatability.The device exhibits fast response,with a rise time and a decay time of 8μs and 566μs,respectively.Meanwhile,the sensitivity of the device to X-ray detection is714μC Gy_air^-1cm^-2and a minimum detectable X-ray dose rate of 36.48 n Gy_airs^-1.Furthermore,the device as a sensing pixel unit shows good imaging ability under 5 V bias voltage.