Towards phase pure CZTS thin films by SILAR method with augmented Zn adsorption for photovoltaic applications

Abstract

Abstract Cu2ZnSnS4 (CZTS) thin films were deposited from a single cationic bath by Successive Ionic Layer Adsorption and Reaction (SILAR) method. Regular SILAR route for CZTS had the drawback of preferential adsorption of copper and tin cations in comparison with zinc. This resulted in Cu3SnS4 (CTS) and Cu2S phases rather than phase pure CZTS films. A modified SILAR route, with a separate bath for Zn2+ ions, circumvented the difficulty and hence led to phase pure CZTS thin films. UV–visible absorption spectra of the CZTS thin films showed absorption coefficients of ~ 104 cm−1 and a band gap of 1.5 eV. Combined van der Pauw and Hall measurements of CZTS thin films showed a resistivity of approximately 1.51 × 102 Ωcm, carrier density of ~ 1.28 × 1017 cm−3, and mobility ~ 0.32 cm2 V−1s−1. A completely solution processed P–N junction was fabricated and characterized by forming glass/FTO/TiO2/CdS/CZTS multilayer.

Keywords

• SILAR
• Solar energy material
• Optical band gap
• Resistivity
• P–N junction