Effect Of Point Defects On The Photocatalytic And Electrical Properties Of ZnO:(S,Se,Te)

ZnO semiconductor is considered a promising photocatalysis material in the third-gen-eration list of semiconductor materials because of its high room-temperature exciton binding energy（60 me V）,high carrier mobility,and stable physical and chemical properties.How-ever,the wide band gap of ZnO restricts its solar absorption in the visible region,which is not conducive to improving the photocatalytic efficiency of ZnO-based photocatalysts.Fur-thermore,the high resistivity and asymmetric unipolar structure of ZnO cause the difficulty of p-type,which severely limits the application of ZnO-based optoelectronic devices.Re-sults showed that intrinsic defects and effective element doping are methods applied to im-prove the photocatalytic and p-type conductivity of ZnO.At present,reports about the re-search of non-metal doped ZnO are abundant,but theoretical studies on the O-homologue S/Se/Te-doped ZnO semiconductors are few.In addition,most of the existing studies have ignored the effects of intrinsic defects and H interstitial impurities unintentionally introduced in the semiconductor fabrication process on ZnO.Therefore,based on first-principles density functional theory,the effects of S/Se/Te-doped ZnO and point defects on the photocatalytic and p-type conductivity of ZnO have been investigated.The effects of group VI elements（S/Se/Te）and point defects on the photocatalytic prop-erties of ZnO system were studied.The Zn₃₆MO₃₅（M=S/Se/Te）model,Zn₃₅MO₃₅（M=S/Se/Te）model,Zn₃₆MO₃₄（M=S/Se/Te）model,Zn₃₆MH_iO₃₄（M=S/Se/Te）model,and Zn₃₅MH_iO₃₅（M=S/Se/Te）model were constructed,and the geometric structure of the sys-tem was optimized respectively.On this basis,the electronic structure and absorption spec-trum were calculated.The results showed that among S,Se and Te doped elements,S-doped ZnO has the smallest lattice change,the smallest supercell volume,the lowest formation energy and binding energy,the easiest doping and the most stable structure.The H interstitial effectively promoted the carrier migration and inhibits the recombination of electron-hole pairs,thereby improving the separation rate of carriers and improving the photocatalytic ac-tivity.The results showed that Zn₃₅SH_iO₃₅ system has the highest hole mobility and hole lifetime,the strongest carrier activity,obvious red shift absorption spectrum and strong re-duction reaction.Zn₃₅SH_iO₃₅ is a promising photocatalyst for hydrogen production from re-duced water.The effects of group VI elements（S/Se/Te）and V_Zn,H interstitial on the p-type con-ductivity of ZnO system were studied.The Zn₃₅MO₃₅（M=S/Se/Te）and Zn₃₅MH_iO₃₅（M=S/Se/Te）model were constructed to optimize the geometric structure and calculate the elec-tronic structure.The results showed that among the three doped elements of S,Se and Te,Te can not promote the conversion of ZnO from n-type semiconductor to p-type semiconductor.H interstitial decreases the conductivity of the doped system along the a direction and in-creases the conductivity of the doped system along the c direction,which indicates that the H interstitial can effectively improve the transport performance of the system along the c direction.The results showed that Zn₃₅SO₃₅,Zn₃₅Se O₃₅ and Zn₃₅SH_iO₃₅ are all p-type de-generate semiconductors.The hole mobility and conductivity of Zn₃₅SO₃₅ are the largest along the a-axis direction,which are 103.60 cm²V^-1s^-1 and 464.39×10² S·cm^-1,respectively;The hole mobility and conductivity of Zn₃₅SH_iO₃₅ system are the largest along the c-axis direction,which are 183.06 cm²V^-1s^-1 and 474.11×10² S·cm^-1,respectively.