Eliminating cracking morphology of solution-processed CZTSSe absorbers by Sn-rich composition engineering. (1st June 2023)

• Record Type: Journal Article
• Authors: Mao, Yang; Guo, Jiajia; Cao, Chun; Ao, Jianping; Liu, Fangfang; Zhang, Yi
• Is Part Of: Materials science in semiconductor processing. Volume 159(2023)
• Publication Date: 2023-06-01
• Subjects: CZTSSe solar cells -- Sn content -- Cracking -- SnSe2 -- MoSe2; CZTSSe Cu2ZnSn(S, Se)4 -- PCE power conversion efficiency -- JSC short-circuit current density -- VOC open-circuit voltage -- FF fill factor -- RS series resistance -- RSh shunt resistance -- Rq root-mean-square roughness -- Wd depletion region width -- NCV free carrier concentration -- Ea the activation energy of the recombination -- Eg band-gap -- Фb blocking contact barrier height -- SEM scanning electron microscope -- XRF X-ray fluorescent spectrometer -- XRD X-ray diffractometer -- AFM atomic force microscopy -- KPFM Kelvin probe force microscope -- J-V current-voltage -- EQE external quantum efficiency; Semiconductors -- Periodicals; Integrated circuits -- Materials -- Periodicals; Semiconducteurs -- Périodiques; Circuits intégrés -- Matériaux -- Périodiques; Electronic journals; 621.38152
• DOI: 10.1016/j.mssp.2023.107388
• Languages: English
• ISSNs: 1369-8001

Abstract

Abstract: Sol-gel method has attracted widespread attention for fabricating highly efficient Cu2 ZnSn(S, Se)4 (CZTSSe) solar cells. However, the volume shrinkage of the gel during the baking process will cause severe cracking of CZTSSe films, which results in shunt paths and significantly deteriorates device performance. Herein, an Sn-rich CZTS precursor is proposed to produce high-quality CZTSSe films, which could relieve the shrinkage forces in CZTS precursor film and compensate for Sn loss of CZTSSe absorbers during selenization process. The effects of Sn content on CZTS precursor compactness and the post-selenization process on the crystallization quality of CZTSSe films are thoroughly investigated. Furthermore, the formation of the MoSe2 interfacial layer and the SnSe2 secondary phase can be regulated efficiently. As a result, the separation and collection of carriers are greatly improved as the depletion region width ( W d ) of the CZTSSe solar cell is broadened. And the difference between the activation energy ( E a ) and band gap ( E g ) has decreased, indicating that the carrier recombination loss caused by the deviated Sn content in CZTSSe films has been effectively reduced. Consequently, the efficiency of the CZTSSe device increased from 7.6% to 9.3% through Sn-rich composition engineering. This study elucidates the role of Sn content in the fabrication of high-quality CZTSSe films and advances the development of ambient air-processed CZTSSe solar cells. Graphical abstract: Image 1 Highlights: Cracking morphology of solution-processed CZTS precursors during the baking process is eliminated by Sn-rich composition. Excess Sn elements in Sn-rich CZTSSe films can be removed through the evaporation of SnSe x vapor at high temperature. To achieve high quality CZTSSe film contact, the MoSe2 interfacial layer and SnSe2 secondary phase are effectively regulated.