| GaAs alloys?such as GaAsN,GaAsSb and GaAsBi?and MAPbX3?X=Cl,Br,I?organic-inorganic hybrid perovskite semiconductor materials show great potential for the application in photoelectric detector,laser and light emitting device in near infrared and visible wavelength range,because of high luminous intensity and tunable photoluminescence?PL?wavelength.However,it was found that impurities and defects caused by the material growth process make a great negative effect on the photoelectric proprerties,which makes the study of material defects and impurities very important.In order to reveal the effect of defects and impurities on the luminescence properties of materials and devices,relaxation and localization transition behavior of the photo-induced carriers at different temperatures and magnetic fields were studied in GaAs alloy and MAPbBr3 hybrid perovskite materials,which reveals the effect of defects and impurities on the luminescence behavior of the material.It provides theoretical support and experimental guidance for optimizing the material synthesis process and improving the material quality and stability in the next step.To solve the problems above,this paper made the following work:1.The photoluminescence and fluorescence lifetime of GaAs0.985N0.015 alloy at low temperature and magnetic field were studied by photoluminescence,fluorescence lifetime and high magnetic field photoluminescence spectra.The temperature-dependent photoluminescence spectra,the co-occurrence spectra of varying excitation power,and the temperature-change fluorescence lifetime results show that carriers in the material were localized due to defects at low temperatures.The fluorescence lifetime is changed from a single component at room temperature to a dual component at low temperature,which correspond to delocalized exciton emission and localized exciton emission,respectively.A blocking of diamagnetic shift could be observed in high magnetic field photoluminescence spectra,which was caused by deep defects,indicating that the cluster states of nitrogen have a great influence on the energy band structure of the material.This research result has important guiding significance for people to control the energy level structure of semiconductors.2.Doping Sb element into the GaAs materials produce a large number of defects.It is different from heavily doped GaAsN,the defect states do not merge into the host energy band and induced some defect-related luminescence.In this paper,the photoluminescence measurements and time-resolved photoluminescence measurements were carried on GaAs0.94Sb0.06 sample to distinguish the sources of the different luminescence peak.Free exciton emission,bound exciton emission and donor-acceptor emission could be observed.The photoluminescence measurement in high magnetic field was carried on the sample to calculate the carrier reduced mass,and exciton emission and non-exciton emission could be distinguished.3.Photoluminescence measurement,time-resolved photoluminescence measu-rement and photoluminescence measurement in high magnetic field were carried on the GaAs0.974Bi0.026 sample.Because of the large locization energy,an obvious splitting of the localized exciton emission and the delocalized exciton could be observed.The localized exciton reduced mass?0.2 m0?obtained from the diamagnetic shift is bigger than the free exciton reduced mass?0.08 m0?,due to the defect-related localization.4.Phase transitions of MAPbBr3 single crystal were investigated by using temperature dependent XRD,PL and transmission measurements.A splitting of the emission peak could be observed at low temperature.The emission peaks could be attributed to the free exciton and bound exciton.The first principle calculations were carried to calculate the electronic structure and analyze the defects in MAPbBr3 single crystal.Defect of anti-site substitution of MA and Br ions matches very well with the experimental defect emission.This research result has important guiding significance for people to understand the origin and function of defects and prepare high-quality single crystals. |
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