Growth and characterization of dual ion beam sputtered Cu2ZnSn(S, Se)4 thin films for cost-effective photovoltaic application

A systematic growth optimization of Cu2ZnSn(S, Se)(4) (CZTSSe) thin films by dual ion beam sputtering system from a single CZTSSe target is presented. It is observed that the ratio of Cu/(Zn + Sn) varies from 0.86 to 1.5 and that of (S + Se)/metal varies between 0.62 and 0.97 when substrate temperature (T-sub) is increased from 100 to 500 degrees C. The crystal structure of all CZTSSe films are identified to be preferentially (1 1 2)-oriented, polycrystalline in nature, and without the existence of secondary phases such as Cu2(S, Se) or Zn(S, Se). The full-width at half-maximum of (1 1 2) diffraction peak is the minimum with a value of 0.12 and the maximum crystallite size 75.11 nm for CZTSSe grown at 300 C. Morphological investigation reveals the achievement of the largest grain size at T-sub = 300 degrees C. The band gap of CZTSSe thin films at room temperature, as determined by spectroscopic ellipsometry, varies from 1.23 to 1.70 eV, depending on T-sub. The optical absorption coefficient of all CZTSSe thin films is >10(4) cm(-1). (C) 2016 Elsevier Ltd. All rights reserved.