Effect of evaporated CdS layer on formation and performance enhancement of flexible Cu2ZnSn(S, Se)4 solar cells. (May 2021)

• Record Type: Journal Article
• Authors: Sun, Luanhong; Shen, Honglie; Hao, Lingyun; Wang, Wei
• Is Part Of: Vacuum. Volume 187(2021)
• Publication Date: 2021-05
• Subjects: CZTSSe -- CdS -- e-beam evaporation -- Conduction band offset; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2021.110098
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Antisite defects induced undesirable open-circuit voltage (Voc) and fill factor (FF) have always been considerable factors that plagued the efficiency enhancement of Cu2 ZnSn(S, Se)4 (CZTSSe)-based photovoltaic devices. Accordingly, sputtered Cu–Zn–Sn–S precursor with e-beam evaporated CdS layer on its top and bottom followed by selenization process was firstly proposed to obtain Cd-alloyed flexible CZTSSe thin film solar cells. The introduced CdS significantly improved crystalline quality and promoted grain growth of CZTSSe absorber. Besides, captured conduction band offset (CBO) exhibited a "cliff-like" structure with the maximum value of −0.15 eV when CdS layer was evaporated on top of Cu–Zn–Sn–S precursor, which largely relieved the band alignment issue in CZTSSe/CdS heterojunction. Interestingly, for CZTSSe prepared with CdS on top, Cd element shows a better uniform distribution in absorber than that with CdS on bottom. Finally, thanks to the evaporated CdS layer on precursor top, the efficiency of flexible CZTSSe thin film solar cell was improved from 2.31% to 4.52%, featuring a Voc of 343.53 mV, Jsc of 27.94 mA/cm 2 and FF of 47.70%. Highlights: Cd-alloyed CZTSSe was obtained by evaporating CdS layer on CZTS precursor. The evaporated CdS layer largely relieved band mismatching of CZTSSe/CdS. CBO exhibited a maximum value of −0.15 eV when CdS was on precursor top. Evaporated CdS on top of precursor can better guarantee the device performance.