| Lead halide perovskite have excellent photoelectric properties and can be widely used in the field of optoelectronic devices.Among them,photodetector（PD）is one of the important photoelectric devices with the ability to accurately convert optical signals into electrical signals,and plays an important role in environmental monitoring,communication,monitoring,image sensors,advanced diagnosis and other related fields of the national economy.Among the numerous photoelectric detection materials,organic-inorganic hybrid halide perovskite polycrystalline thin films have poor stability and are difficult to be commercialized in a short time.All inorganic halide perovskite materials have stronger ionic bonds and better stability than organic-inorganic hybrid halide perovskite materials.At the same time,lead halide perovskite single crystal materials without grain boundaries have superior carrier transport characteristics.Therefore,all inorganic lead halide perovskite single crystals can be used as ideal materials for the preparation of high-performance photodetectors.However,with the in-depth study,it was found that the growth of all inorganic halide perovskite single crystal was difficult and the narrow-band photoelectric detection performance was low,which hindered the further commercial application of all inorganic perovskite single crystal.Based on the above problems,the scientific and technical problems existing in the crystal growth,device preparation,defect passivation,interface carrier transport and recombination mechanism of all inorganic halide perovskite single crystal were systematically studied in this paper,and a high-performance and stable single crystal photoelectric detector was constructed,and its intrinsic physical properties were systematically studied,The influence of interface regulation on charge implantation,ion migration and photoelectric detection performance gain of all inorganic perovskite single crystal is revealed,and the influence mechanism of composition regulati on on carrier transport performance of single crystal is expounded.The main research contents and results of this paper are as follows:1.Objective to explore the growth mechanism of all inorganic lead halide perovskite single crystal CsPbBr3.The CsPbBr3 single crystal was grown by solution method.The growth of CsPbBr3 single crystal was characterized from the phase and optical properties.It was proved that the crystal grown by solution method was pure CsPbBr3 single crystal with less defects.At the same time,in order to solve the size limitation of CsPbBr3 single crystal grown by solution method,we tried to synthesize adjustable large-size CsPbBr3 crystal under air conditions by using similar ceramic sintering process for reference.Combined with thermal analysis,the phase transition temperature point from room temperature to melting range of CsPbBr3 was marked,and the sintering mechanism was designed and adjusted based on this,At the same time,the quality of the sintered CsPbBr3 samples was further improved by secondary sintering.2.The narrow band photoelectric detection performance of CsPbBr3 single crystal was studied.Based on all inorganic halide perovskite CsPbBr3 single crystal material,a non-traditional,positive bias,high narrow-band single crystal PD was prepared.The influence of electron acceptor C60 on CsPbBr3 single crystal and narrow-band photodetectors was investigated.It was found that the introduction of C60 layer and surface trap could play a key role in enhancing the external quantum efficiency（EQE）of CsPbBr3 single crystal narrow-band PD.The high-performance narrow-band PD shows obvious narrow-band characteristics at 6 V positive bias voltage,with a FWHM of 16 nm and a specific detection rate（D*）of 6.5×1010 Jones at 550 nm,the bandwidth of-3 dB(f-3dB)is 2776 Hz,and the calculated carrier mobility（μ）is 6.7 cm2 V-1s-1.This is mainly because the positive bias leads to the migration of Br ions and Cs ions to the anode and cathode respectively,thus inducing self doping in the single crystal,forming a p-i-n junction,which significantly improves the rectification behavior in the photodiode,so that the photo generated charge and injected charge in the positive bias device are conducive to improving the EQE of the device.Further,the photodetector made of CsPbBr3 wafer prepared by sintering method still has narrow-band detection performance,and the D*of the prepared narrow-band PD at 550 nm is 2.4×109 Jones.The FWHM is about 16 nm and the f-3dB is 481 Hz.Because of its adjustable synthesis size and simple preparation process,it has a good application prospect.3.Based on the halogen element doping of CsPbBr3 crystal by solution method,it is proved that Cl ion is easier to be doped into the lattice structure of CsPbBr3 crystal by solution method,while I ion has anisotropy in solution growth,which weakens the formation energy and leads to only a small amount of doping in the crystal.The photoelectric detector made of halogen doped CsPbBr3 crystal has narrow-band detection performance,but also has higher detection performance under positive bias voltage.The specific detection rate D*of narrow-band PD prepared from CsPbBr2.78Cl0.22 single crystal is 2.59×1010 Jones at 6 V positive bias voltage,the D*of PD prepared from CsPbBr2.55Cl0.45 single crystal is 9.40×108 Jones,the specific detection rate D*of PD prepared from CsPbBr2.98I0.02 crystal is 1.12×1010 Jones,and the band gap of narrow-band photodetectors made of halogen doped CsPbBr3 crystals can be adjusted effectively.4.Rubidium doped Cs（1-x）RbxPbBr3 single crystal was grown by low-cost solution growth method,and its crystal structure was characterized.It was proved that it was single crystal and rubidium was successfully doped into the single crystal.The single crystal CsPbBr3 was made into a high-performance X-ray detector.Under the electric field of 20.1 V mm-1,itsμτValue is 4.9×10-4 cm2 V-1,sensitivity 918μC Gyair-1 cm-2.The Cs（1-x）RbxPbBr3 single crystal doped with a small amount of Rb（0.037%）has lower trap density,higher resistivity and higher charge mobility,which makes itμτThe value reached 7.2×10-4 cm2 V-1,and the sensitivity of single crystal X-ray detector prepared with this doping amount is up to 8097μC Gyair-1 cm-2.At the same time,the study also shows that further increasing the rubidium doping rate（0.366%）will reduce the X-ray detection performanceμτlow value(1.1×10-4 cm2 V-1)and poor X-ray sensitivity(241μC Gyair-1 cm-2).XPS characterization showed that a small amount of Rb doping increased the orbital coupling between Pb andBr atoms,which improved the carrier transport and collection efficiency.The mechanism of A-site doping in CsPbBr3 single crystal affecting the device performance was clarified.In this paper,the detection performance of photodetectors based on all inorganic lead halide perovskite CsPbBr3 single crystal was improved by using component design and interface control.The mechanism of component design controlling the photoelectric performance of materials and the mechanism of high narrow-band detection performance of excitation devices by applying positive bias voltage under interface control were clarified.All inorganic lead halide perovskite single crystal materials were designed,It provides experimental basis and theoretical support for the construction of high-performance photodetectors. |
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