| Metal halide perovskite materials(MHPs)have a wide range of applications in photovoltaic fields such as solar cells and light-emitting diodes due to their outstanding optoelectronic properties,easy fabrication and low cost.At the same time,some metal halide perovskite materials have some defects due to their own components,such as slightly poor long-term stability or optical performance in external environments such as heat/ultraviolet rays and ambient oxygen/humidity,making the There are limitations in the development of semiconductor materials,which in turn lead to certain obstacles from the laboratory to the actual market application.In order to avoid the above problems,researchers proposed to use ion doping or substitution to control the optical properties or structure of the material.Among them,A/B-site doping or substitution of MHPs has become the focus of recent research.However,after a large number of studies,it has been found that although the stability and optical properties of MHPs can indeed be improved by doping or substituting components,the properties or structure of the material can only be adjusted by ion doping or substitution,which is not only inefficient but also difficult to precisely control.Recently,high-pressure technology with the characteristics of high efficiency,energy saving,and no pollution has become one of the effective means of regulating the physicochemical properties of a new generation of materials.It can precisely control the structure and properties of MHPs without changing the composition,so as to achieve the purpose of improving the stability of the material and optimizing the optical properties such as the band gap.Therefore,on the basis of ion doping or substitution,this paper uses high-voltage technology to further explore the effect of high pressure on the optoelectronic properties and crystal structure of MHPs,laying a solid theoretical foundation for the application of this material in more fields in the future.In this paper,we select one representative A/B-site doped metal halide chalcogenide material as the object of study.First,we synthesized(CH3)3SPb I3crystal by introducing sulfur ion to replace amine ion at room temperature.On this basis,we first investigated the optical properties and structural pressure response of the(CH3)3SPb I3crystals using the high-pressure DAC technique in combination with in situ high-pressure fluorescence spectroscopy,in situ high-pressure UV-Vis absorption spectroscopy,and in situ high-pressure Raman spectroscopy.The results of the obtained experimental data show that the optical band gap of(CH3)3SPb I3gradually narrows from the initial 2.86 e V to 1.96 e V during the entire pressurization process(0-20.1 GPa),exhibiting an optical band gap compression rate of up to 31.5%.The bandgap narrowing and piezochromic processes are fully reversible.In addition,we observed a 20-fold fluorescence enhancement in the low pressure range(0-3.2 GPa).Based on previous reports in the literature,we speculate that these optical changes can be attributed to the fact that the symmetry of[Pb I6]4-octahedra decreases under the effect of high pressure and that the crystal structure undergoes a phase transition from hexagonal phase(P63mc)to monoclinic phase(Cc)at 3.1 GPa.Subsequently,we prepared Cs Zr1-xTexCl6(x=0.002,0.004,0.006,0.008,1)crystal powder with five doping ratios by high-temperature reactor method,and the optical properties of the representative Cs Zr1-xTexCl6(x=0.004)crystal powder were investigated using the same high-pressure DAC technique.The experimental results showed that the fluorescence emission center of Cs Zr1-xTexCl6(x=0.004)crystal powder showed a blue shift followed by a red shift with increasing pressure,and was accompanied by a four-color fluorescence color modulation phenomenon of orange—light yellow—light green—green,and the unloading pressure was completely reversible.More notably,the sample still has a strong fluorescence intensity under high pressure up to 32.2 GPa,which is relatively rare.At the same time,we observed that the energy band gap of the sample remained relatively stable at pressures up to21.0 GPa,reflecting the excellent pressure resistance of Cs Zr1-xTexCl6(x=0.004)crystals.Based on previous literature reports,we speculate that such optical changes can be attributed to[Te Cl6]2-octahedral distortion under pressure.The experimental results in this thesis can indicate that the high-pressure technique has an excellent modulating effect on the optoelectronic properties of A/B-site doped metal halide based chalcogenide materials,which provides a new idea for the design of semiconductor materials with excellent optoelectronic properties. |
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