Different heat treatment effects on the microstructure and optoelectronic characteristic of Cu2ZnSn(S Se)4 thin films

Abstract

The Cu2ZnSnS4 (CZTS) nanocrystallites were synthesized by the heating-up process The ligands exchange process was used to reduce the residual carbon on the CZTS particle surface CZTS thin films with a thickness of about 500 nm were deposited onto the Mo/SLG substrate by using spin coating process In this study two methods were used to densify and promote CZTS grain growth: direct selenization and two-stage heat treatment The direct selenization process is to selenize CZTS thin films in a graphite box with selenium vapor at 500 ℃ to promote the grain growth The two-stage sintering is to pre-sinter CZTS thin films under nitrogen atmosphere for 1 h to promote the densification before the selenization The different selenization time pre-sintering temperature and coating times effects on the electric properties densification microstructures and chemical composition uniformity of CZTSSe films were investigated A p-type CZTSSe film with the hole concentration of 7 89×1019 cm-3 the mobility of 24 3 cm2 V-1 s-1 and the resistivity of 3 27×10-3 ?-cm can be obtained by direct selenization of the twice spin-coated CZTS film at 500 ℃ for 15 min The CZTSSe thin film prepared by two-stage heat treatment (pre-sintering temperature: 250oC and selenization temperature: 500oC/15 min) had electrical properties with the hole concentration of 1 21×1019 cm-3 the mobility of 27 5 cm2 V-1 s-1 and the resistivity of 1 88×10-2 ?-cm The electrochemical process of cyclic voltammetry can effectively remove Cu2-xSe particles on the CZTSSe surface leading to a higher photocurrent (1 02 mA)

Date of Award	2020
Original language	English
Supervisor	Hsing-I Hsiang (Supervisor)