Fabrication And Characteristic Research Of High-performance CH₃NH₃PbCl₃ Ultraviolet Detector

Ultraviolet light detection technology has a very wide range of applications in military and civil fields such as ultraviolet light communication,missile tracking and early warning,flame monitoring and biomedicine.Organic–inorganic hybrid lead halide perovskite materials have attracted the attention of many researchers due to their plenty of excellent optoelectronic properties such as tunable direct band gaps,large light absorption coefficients,and excellent carrier transport characteristics.Therefore,Organic–inorganic hybrid lead halide perovskites are considered as one of the promising candidates in optoelectronic and electronic applications.Compared with nano crystals such as quantum dots and polycrystalline thin films,perovskite single crystal materials not only have the above-mentioned common advantages of perovskite materials,but also have other advantages such as fewer grain boundaries,lower carrier concentration,lower trap density,etc.As a result,photodetectors based on perovskite single crystals have better stability and higher performance.Among numerous organic-inorganic hybrid perovskite materials,CH₃NH₃PbCl₃ is considered as an ideal material for ultraviolet detection devices due to its band gap of about 3.1 eV at room temperature.However,the performance of photodetectors based on CH₃NH₃PbCl₃ single crystals is much lower than that of devices based on CH₃NH₃PbI₃ and CH₃NH₃PbBr₃ materials.The lower performance of these devices may be attributed to the relatively poorer crystalline quality of the CH₃NH₃PbCl₃ single crystals prepared by the traditional crystallization process,as a result,the application development of CH₃NH₃PbCl₃ based photodetector was restricted.In addition,many studies have shown that a composite structure device prepared by combining organic-inorganic hybrid perovskites and inorganic semiconductor materials can effectively improve the performance of the photodetector and the long-term device stability.In addition,many studies have shown that a composite structure device prepared by combining an organic-inorganic hybrid perovskite and an inorganic semiconductor material can effectively improve the performance of the detector and the long-term work stability.In allusion to the above-mentioned problems,this paper starts with the improvement of the crystal quality of CH₃NH₃PbCl₃,and carries out related research work,the specific content is as follows:（1）Based on the traditional inverse temperature crystallization method,by fine-tuning the control of crystal nucleation and crystal growth progress,a high-efficiency two-step temperature crystallization method was developed,which greatly improved the crystal quality of the single crystal product.The single crystal obtained by this method has the narrowest half-peak width of the rocking curve（⁰.0447°）,the lowest trap state density（⁷.9×10⁹/cm³）,and the largest carrier mobility（⁶4 cm²/V?s）among the CH₃NH₃PbCl₃ materials reported so far.All these above results show this crystal has the highest crystal quality.（2）The metal-semiconductor-metal（MSM）structure UV detector was fabricated by using the obtained high-quality CH₃NH₃PbCl₃ single crystal.The device has a high responsivity of 3.73 A/W at 415 nm,a high detection of 9.97×10 ¹¹ Jones,and a faster response speed with a rise time of 130 ns,which are much better than those of any CH₃NH₃PbCl₃ devices previously reported.In addition,the device can maintain long-term work stability for more than 50 days in the atmosphere without encapsulation.The excellent working performance of the device is inseparable from the higher crystalline quality of the CH₃NH₃PbCl₃ single crystal obtained by the high-efficiency stepwise crystallization method.（3）ZnO microwires were grown by the CVD method,and then a layer of CH₃NH₃PbCl₃ crystals was deposited by using the high-efficiency two-step temperature crystallization method on the microwire to form a CH₃NH₃PbCl₃/ZnO heterojunction structure UV photodetector.This device has obvious rectifying characteristic and fast response speed characteristic.In addition,the device has two working modes,normal incidence and back incidence,and its response corresponds to the ultraviolet&visible and pure ultraviolet respectively.The working mode of the device can be selected according to the wavelength of the measured optical signal to meet different needs.The high-quality CH₃NH₃PbCl₃ layer prepared by the stepwise temperature crystallization is the basis for successfully constructing heterojunction photodetector.