Preparation Of Cation-doped CZTS/Bi₂S₃ Heterojunction By Pulsed Laser Deposition And Its Photoelectric Properties

Cu₂ZnSnS₄（CZTS）has attracted extensive attention and research due to its excellent photoelectric performance and low preparation cost in recent years.In this study,CZTS thin films were grown by room-temperature（RT）pulsed laser deposition（PLD）,and the antisite defects in CZTS were suppressed by cation doping.The heterojunction was formed by coupling CZTS with with the electron transport layer（ETL）Bi₂S₃,and its photoelectric properties were explored.The specific work has been done as following:CZTS target was synthesized by solid-state sintering method.CZTS films were prepared by PLD technique at room temperature with in-situ annealing at different temperatures.The photoelectric test results showed that the CZTS film in-situ annealed at 400°C had the best absorption of visible light（Vis）and the band gap was suitable for Vis absorption.At the same time,in-situ annealing technology can also avoid post-sulfidation process and optimize the film growth.Furthermore,ETL Bi₂S₃ was combined with CZTS to construct the CZTS/Bi₂S₃ heterostructure in order to improve its photoelectric performance.The chronoamperometry measurement showed that,compared with the single-layer CZTS film,the photoelectric response time constants of photocurrent rising and decay for the bilayer heterojunction in Vis can be reduced by one order of magnitude,reaching up to 0.34 s and 0.21 s,respectively.In order to suppress the ubiquitous antisite defects of Cu _Zn and Zn _Cu in pure CZTS,Cu₂(Zn_xFe_1-x)Sn S₄（CZFTS,x=0～1）films were synthesized by RT-PLD by using magnetic Fe element replacing Zn,and the optimal doping ratio x=0.75 was obtained by analysis.CZ_0.75F_0.25TS/Bi₂S₃ heterostructure was formed by coupling Bi₂S₃ with CZ_0.75F_0.25TS film;the in-situ PLD deposition process effectively optimized the CZ_0.75F_0.25TS-Bi₂S₃ interface.The photoelectric response speed of heterojunction was further improved than that of CZTS/Bi₂S₃ structure,and the rise and decay response time constants reached up to 0.12 s and 0.04 s,respectively.Further,(Cu_1-xAg_x)₂ZnSnS₄（CAZTS,x=0.1）thin films were synthesized by RT-PLD by using Ag element to replace Cu.On this basis,CAZTS/Bi₂S₃heterojunction was prepared and the chronoamperometry test showed that the photoelectric response speed of such heterojunction was faster than that of the CZTS/Bi₂S₃ structure,and the rise and decay response time constants reached up to0.03 s and 0.02 s,respectively.