Preparation And Performance Control Of CsPbBr₃ Based Photodetectors

Perovskite semiconductors have become the preferred material for the next generation of optoelectronics because of their easy to manufacture and rich elements.Solution-treated mixed perovskite(ABX₃,in which A=CH₃NH₃⁺or MA,HC(NH₂)₂⁺or FA;B=Pb⁺,Sn⁺;X=Cl^-,Br^-,I^-)are the most promising semiconductors.However,A-site-based organic cations are usually extremely unstable in moisture,oxygen,light and high temperature environments.This is due to the internal instability of the organic cation itself.Therefore,the use of inorganic cations instead of organic cations to form all-inorganic perovskite at site A can overcome its stability,do not deteriorate the transport performance,and maintain the efficiency of the device.Therefore,all-inorganic perovskite,especially CsPbBr₃,has received considerable attention.CsPbBr₃ in all-inorganic lead halide perovskite(Cs Pb X₃)is a kind of direct band gap semiconductor material,and has remarkable optoelectronic properties such as high absorption coefficient,high carrier mobility and long diffusion length.It shows a good development trend in many fields,such as solar cells,photodetectors,high energy ray detectors,light emitting diodes and so on.Secondly,CsPbBr₃ perovskite materials are favored by researchers because of their low cost and easy to operate solution treatment process and potential applications in optoelectronic devices.CdSe nanoribbons(NBs)are direct bandgap semiconductors with 1.7 e V bandgap and excellent optical properties such as carrier transport.Therefore,their combination with all-inorganic perovskite layers with high photon absorption may pave the way for new high-performance optoelectronic devices.Based on this,firstly,CsPbBr₃ micron line arrays(MAs)and CsPbBr₃ micron lines(MWs)were synthesized by two methods,and their optoelectronic properties were studied systematically.Secondly,CdSe NBs were grown by chemical deposition(CVD),and CsPbBr₃ MW/CdSe NB hybrid optoelectronic devices were constructed.The test and analysis of the optoelectronic properties of hybrid devices show that compared with a single CsPbBr₃ device,the hybrid devices show a wide spectral response(from ultraviolet to visible light)and their optoelectronic properties have been greatly improved.We give a reasonable explanation for the microphysical mechanism of improving the optoelectronic performance of hybrid structure devices.The main contents and results of this thesis are as follows:1.A large area CsPbBr₃ MAs with high order and high crystal quality was synthesized by PDMS template-assisted method.Scanning electron microscope morphology characterization,transmission electron microscope microstructure analysis and X-ray phase analysis showed that the single crystal CsPbBr₃ MAs with high crystal quality was obtained,and the optical properties of CsPbBr₃ MAs were analyzed by UV-vis and PL.Then the CsPbBr₃ MAs photoelectric detector was fabricated by evaporation electrode in the electron beam evaporation system,and its photoelectric properties were tested.The CsPbBr₃ MAs photodetector has a good on/off photocurrent ratio(9.02×10~3),a high detection rate of 1.43×10¹¹ Jones,a high response rate of 4.55 A/W and a fast response speed of 49/3 ms.More importantly,after two months of storage in the air,the photocurrent of the photodetector is almost unchanged and the stability is remarkable.This study shows that it is possible to fabricate large-scale and high-performance optoelectronic devices with CsPbBr₃ MAs.2.Firstly,CsPbBr₃ MWs were synthesized by in-plane self-assembly method.The microwire samples were characterized and the optoelectronic properties of the devices were tested,in which the current switch ratio was 1.11×10~3,the external quantum efficiency was 631.94%,the detection rate was 2.9×10¹⁰ Jones,and the responsivity was 2.7 A/W.Then we used CVD method to grow CdSe NBs.The morphology characterization of scanning electron microscope and microstructure analysis of transmission electron microscope show that the obtained CdSe NBs has a uniform width,smooth and smooth surface,and is a single crystal.The prepared CdSe NBs is transferred to CsPbBr₃ MWs to form CsPbBr₃ MWs/CdSe NB composite optoelectronic devices,and the optoelectronic properties of the composite devices are tested and analyzed.The results show that the spectral response range of the composite device(300-740 nm)is obviously wider than that of a single CsPbBr₃ MW(300-550nm)device.The switching ratio of the CsPbBr₃ MW/CdSe NB hybrid optoelectronic device is as high as 5.02×10~4,which is 45.5 times that of the pure CsPbBr₃ MWs device;the maximum response under the monochromatic light irradiation of 530 nm is1.63×10~3 A/W,which is 603.7 times that of a single CsPbBr₃ MW device;the external quantum efficiency is 3.8×10~5%,which is 601.4 times that of a single CsPbBr₃ MW device;finally,the rising and falling edges of the device are 16 and 34 ms,respectively.The hybrid device not only broadens the spectral response range,but also promotes the effective separation of carriers,which significantly improves the optoelectronic performance of the device,and provides useful guidance for the development and application of CsPbBr₃-based optoelectronic devices.