Study On The Preparation Of Lead-Free Halide Rb₂CuBr₃ And Its Applications In Ultraviolet Photodetectors

Ultraviolet（UV）photoedetector refers to the device that converts the incident UV radiation signal into the electrical signal,which has very important applications in both military and civilian fields,such as flame detection,space communication,biomedical analysis,marine oil pollution monitoring,missile warning and tracking and so on.Recently,Organic-inorganic lead halide perovskite materials have been extensively explored in the UV photodetection field by virtue of their excellent photoelectric properties and convenient preparation process.However,due to its limited adjustable band gap range（410-700 nm）,lead toxicity and instability of organic ammonium salts,which greatly limited the development of such materials in UV photodetection filed.Compared with organic-inorganic lead halide perovskite,the new inorganic lead-free perovskite not only has a wide variety and rich crystal structure,but also has good chemical stability and application universality.Therefore,it is imperative to find environment-friendly and stable lead-free perovskite materials as the light absorption layer for UV region to solve the above problems.In addition,UV photodetectors based on lead-free perovskite are rarely reported.In this paper,lead-free copper halide Rb₂CuBr₃ is selected as the research object,which has the characteristics of one-dimensional chain structure that expected to achieve high carrier transmission efficiency.The one-dimensional lead-free copper halide Rb₂CuBr₃ microwires（Rb₂CuBr₃MWs）with high crystallity,uniform width,smooth surface and high absorbance are prepared by supersaturated crystallization method.An UV photoelectric detector based on Rb₂CuBr₃ MWs is designed and its photoelectric detection performance is investigated.The main contents and innovations are as follows:1.We studied the growth process,morphology optimization,size control,stability and optical properties of Rb₂CuBr₃ MWs.Firstly,the sample with high crystallization quality and smooth and uniform surface was obtained by preparing the precursor solution with a certain proportion of materials.Then,the size of Rb₂CuBr₃ MWs were regulated by changing the concentration of the precursor solution.Finally,the morphology,crystallinity,optical properties and environmental stability of Rb₂CuBr₃MWs（including heat resistance,water and oxygen in air and UV light）were systematically tested and analyzed.2.A metal-semiconductor-metal（MSM）photoelectric detector based on a single Rb₂CuBr₃ MWs photoconductivity was designed and fabricated,and the photoelectric performance and working stability of the device were studied.It is found that the device achieved a responsivity of 113.64 mA/W,a specific detection rate of 1.23×10¹¹ Jones,and a response speed of 69.31/87.55 ms under 265 nm UV light and 5 V bias voltage.At the same time,the device without any package showed outstanding stability and repeatability.After being stored in ambient air for 2 weeks,the light detection ability basically remained unchanged.In addition,the fabrication of flexible devices showed remarkable flexural resistance.3.In order to further optimize the device detection performance based on Rb₂CuBr₃ single crystal wire,we combined the p-Rb₂CuBr₃ with n-GaN to design and prepare the n-GaN/Rb₂CuBr₃ heterojunction photodetector.The device has self-driving characteristics,that is,it can work without external bias.The most important is that its photoelectric performance was greatly improved compared with the photoconductive device.The switching ratio of the heterojunction device is 10⁵,and the responsiveness,specific detection rate and response speed are 375 mA/W,3.11×10¹³ Jones and 22.25μs/0.36 ms,respectively.In addition,the proposed heterojunction detector also shows good stability and repeatability.Meanwhile,the unpackaged devices showed excellent storage stability after being stored in ambient air for 2 months.In summary,one-dimensional ternary lead-free copper halide Rb₂CuBr₃ material not only has the advantages of simple preparation process,low cost,and high carrier efficiency transmission characteristic,but also shows excellent stability,which meets the application requirements of environment-friendly UV photodetector.It is expected to provide a feasible solution for the preparation of stable and environmentally friendly UV photodetectors.