Spin-coated CZTS films prepared by two different precursor mixing regimes, at room temperature and at 150 °C

Abstract

In this paper, we examine the impact of the precursor's mixing temperature and mixing protocol on the crystal structure and morphological and optical properties of Cu 2 ZnSnS 4 (CZTS) thin films. Four samples of CZTS thin films were synthesized with the sol-gel spin coating technique by previously mixing precursors at (a) 150 °C and (b) room temperature (RT), either (i) all at once or (ii) through sequential adding the individual chemicals 30 min apart. SEM-EDX, XRD, Raman and Visible spectroscopy analysis showed that sample 150°C-ST (chemicals mixed at the same time at 150 °C) fulfilled all the theoretical stoichiometric criteria (poor in Cu, rich in Zn) for the high-quality CZTS absorbers. The larger grain size (850 nm) and crystallite size (73.96 nm), lower strain ( 0.49 × 10 − 3 ) and band gap E g = 1.44 e V which is closest to the Shockley–Queisser limit for single junction solar cells (1.34 eV).