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Investigating the Role of Selenium-Ion Concentration on Optoelectronic Properties of the Cu2ZnSn(S1–xSex)4 Thin Films

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journal contribution
posted on 01.06.2020, 19:34 authored by Satish S. Patil, Kishorkumar V. Khot, Sawanta S. Mali, Chang Kook Hong, Popatrao N. Bhosale
Recently, deposition of Cu2ZnSn­(S1–xSex)4 (CZTSSe) thin films directly onto substrates via a cost-effective hydrothermal route has become a promising approach for their further development. We investigated the influence of the Se2– ion content on the growth and optoelectronic properties of CZTSSe thin films. The synthesized CZTSSe nanocrystalline films showed considerable refining in their optoelectronic and photovoltaic properties. The optical absorption of CZTSSe films revealed that the band gap energy decreases from 1.5 to 1.42 eV with increment in the Se2– ion concentration. Structural analysis confirms the improvement in the crystallinity with the kesterite crystal structure, which was also validated by (112) plane shifting with varying Se2– ion concentration. Surface morphological and structural analyses confirm the formation of a highly uniform, well-crystalline, and compactly interconnected nanosphere-like morphology. Compositional analysis confirms that the CZTSSe film shows desired stoichiometric ratios with Cu, Zn, Sn, S, and Se in +1, +2, +4, −2, and −2 oxidation states, respectively, in Cu2ZnSn­(S1–xSex)4 compositions. The promising composition is observed for Cu2ZnSn­(S1–xSex)4 films with x = 0.075 Se-ion concentration. Photoelectrochemical solar cells assembled for the CZTSSe photoelectrode exhibited a current density (Jsc) of 4.64 mA/cm2 and an open-circuit voltage (Voc) of 542 mV, leading to a photoconversion efficiency of 3.62%. Our electrochemical impedance spectroscopy suggests lower values of charge-transfer resistance (Rct) generated at the photoelectrode–electrolyte interface, which is in well agreement with photoelectrochemical solar cell performance.