CVD Method Synthesized All-inorganic Perovskite And Its Development Of Optoelectronic Devices

In the last century,the developments of semiconductor devices,including photodetectors,large-scale intergrated circuits and various optoelectronic devices played a cruicial role in the modern information technology revolution,and triggered a new global industrial revolution.These are inseparable from the development and application of seniconductor-based optoelectrinic devices.In recent years,the ABX₃structure of organic-inorganic hybrid perovskite materials,as a rising star in the field of semiconductor optoelectronic materials science,has a tunable bandgap,ultra-fast charge generation rate,high average electrom/hole mobility and long carrier lifetime.However,the poor intrinsic stability of organic-inorganic hybrid perovskites hinders their application in practical industries greatly.All-inorganic perovskites by replacing the organic group with an inorganic atom Cs at the A-position,can effectively solve the stability problem.All-inorganic perovskite CsPbX₃?X=Cl,Br,I?maintain the excellent properties with more stable structure compared to the organic-inorganic hybrid perovskites.Thin film is the preferred structure for preparing semiconductor optoelectrinic devices.The industrial integration and application of traditional IV,III-V and II-VI semiconductor materials are based on the successful development of high-quality thin film materials and the growth of industrial scale.Compared with polycrystalline CsPbX₃,CsPbX₃ single crystal film has excellent carrier transport performance due to low defect level,good grain boundary quality and smooth surface.However,it is difficult to prepare high quality CsPbX₃ thin films with micron size by the traditional solution synthesis method.There are few reports on high performance perovskite single crystal optoelectronic devices.In this paper,high quality CsPbBr₃ thin films are prepared by chemical bapor deposition?CVD?growth method,which can avoid solvent-induced detects,ensure uniform deposition of insoluble raw materials,and accurately control reaction paratemters such as temperature and airflow.We successfully synthesized CsPbBr₃ microcrystalline films on different substrates by CVD using PbBr₂ and CsBr as source,and studied their applications in opoelectronic devices.In general,the specific work is as follows:?1?Successfully growing CsPbBr₃ microcrystals with different morphologies on GaN substrate:CsPbBr₃ microcubic crystals with a side length of 10?m are grown at a temperature of 600°C and a pressure of 150 Pa;A dense CsPbBr₃ microcrystalline film will grow on the GaN substrate at a temperature of 600°C and a pressure of 200Pa;higher growth temperature?620°C?will cause the difficult deposition of CsPbBr₃;low temperature?580°C?will cause uncontrolled CsPbBr₃ deposition,forming a random ingot.?2?The as-synthesised CsPbBr₃ microcubic crystal has high quality,smooth surface and good morphology.It has two PL peaks with bandedge emission and above-bandgap emission,and has good two-photon absorption characteristics.The WGM laser can be achieved by exciting CsPbBr₃ with a 800 nm femtosecond pulsed laser.?3?A self-powered photodetector based on full inorganic layers of p-GaN/CsPbBr₃/n-ZnO was constructed.The layer interfaces within detector was excessively flat,and the perovskite film was uniform without holes.The introduction of GaN and ZnO layers greatly reduces dark current,and the constructed p-i-n structure has an energy conversion efficiency of 20%,a responsivity of 89.5 mA/W,and a detectivity of 10¹⁴ Jones.The rise time and fall time of the device measured by a high frequency chopper are 100?s and 140?s,respectively.It is clarified that the strong built-in field introduced by GaN and ZnO layers can promote the separation of photogenerated electron-hole pairs of the device,thereby improving the photoresponse speed.The performance test of the detector at different temperatures also comfirms that the device has strong thermostability.?4?A high quality CsPbBr₃ microcrystalline striped film was successfully grown on the interdigital ITO electrode by CVD method.The as-grown CsPbBr₃ microcrystals have high crystal quality,few grain boundaries and large bulk.The Schottky contact was formed with a barrier heigth of 0.75 eV and a threshold voltage of 9 V at CsPbBr₃/ITO interface,which is better than the previous reports on CsPbBr₃.The introduction of the back-to-back Schottky junction can effectively reduce the dark current of the photodetector,which can be achieved without complicated processes.The device exhibits high photodetection performance:current on/off ratio of 10⁴,a responsivity of 3.9 A/W?at 15 V bais?,detectivity of 3.8×10¹² Jones,fast response speed?rise time:0.22 ms,fall time:0.45 ms?and a wide operating voltage range.In addition,the device shows good stability and maintains the components at high temperature.After naturally cooling to the room temperature,the photocurrent will recover to its inital level.