The Electrical Transport Properties Of Cuprous Iodide Under High Pressure

Cuprous iodide(CuI),as an inorganic copper-based p-type semiconductor material,has attracted much attention in recent years due to its advantages of low cost and easy preparation.CuI is characterized by its wide optical direct band gap,high hole mobility and visible light transparency of thin film,and therefore has been widely used in the preparation and research of perovskite solar cells,semiconductor thin film transistors,light-emitting diodes and other optoelectronic devices.As we all know,the crystal structure and the band structure of semiconductor materials usually change under pressure.,as a result,the materials may show new properties and phenomena that they do not have before.Pressure can also induce the occurrence of structural transition of semiconductors,and the change of internal structure leads to the abnormal conductive behavior of materials.In this paper,CuI was tested by in-situ high pressure Raman spectroscopy,resistivity and hall effect based on diamond anvil device.The electrical transport properties of CuI under pressure within 30 GPa was studied systematically,the relationship between various electrical parameters and the structural transition was discussed,the intrinsic conductive mechanism of material was explained by combining with the structural transition.The results are as follows:(1)According to the analysis of the Raman test results,the Raman vibration peak representing TO horizontal optical mode has an inflection point near 1.6 GPa,a second inflection point at 5 GPa and a wide peak at 117.5 wave number at 2.1 GPa,.Combined with the X-ray diffraction results under high pressure,we suppose that the change of Raman vibration peak within this pressure range is caused by the structural transition of the sample under high pressure.(2)We got the resistivity of cuprous iodide within 30 GPa by means of in-situ resistivity measurement under high pressure.the resistance rate increased with the increase of pressure three times change obviously,from the test results,sample resistivity increases with pressure decreases obviously;In the range of 1.5-4 GPa,the resistivity of the sample increased significantly with the increase of pressure.In the range of 4-18 GPa,the resistivity of the sample decreases significantly with the increase of pressure,and then decreases gradually,and finally becomes flat.After 18 Gpa,the resistivity of the sample was no longer obvious with the pressure trend.(3)To further reveal the change of electrical transport properties of CuI under pressure,we measured in-situ hall effect of high pressure,and studied the transport behavior of carriers of CuI under high pressure from the perspective of internal mechanism.The hall coefficient is always positive during the compressed process,which indicates that the conductive type of carriers in the sample is always dominated by holes.Before 1.5GPa,the sample carrier concentration increased sharply with the increase of pressure.After 1.5 GPa,the mobility remained unchanged,and the carrier concentration suddenly decreased.After 4 GPa,carrier concentration and mobility both increased.When the pressure increased to 18 GPa,the carrier concentration increased slowly with the increase of pressure,and the mobility decreased with the change of pressure.Combined with the variation trend of resistivity under pressure,we explain the internal mechanism of the change of carrier concentration and mobility under pressure modulation in detail.