Novel hydrothermal route for synthesis of photoactive Cu 2 ZnSn(S,Se) 4 nanocrystalline thin film: efficient photovoltaic performance

This work reports single-step deposition of Cu2ZnSn(S,Se)4 (CZTSSe) nanocrystalline film via simple and non-toxic hydrothermal route. The hydrothermal growth of CZTSSe multinary nanocrystalline film formation based on Ostwald ripening law which results in highly oriented nanocrystalline nanoflakes. The UV–Vis spectroscopy illustrates that maximum absorption was observed in the range of 650–700 nm with band gap energy of 1.48 eV. Structural studies confirm the formation of pure-phase kesterite crystal structure. Further, Raman shift at 174 cm−1, 196 cm−1 and 236 cm−1 shows A1 mode of vibration corresponding to kesterite structure. Densely packed and compact nanoflake formation was observed in SEM studies. Compositional analysis confirms the stoichiometric film formation with expected valence states of CZTSSe stoichiometry: Cu+, Zn2+, Sn4+, S2− and Se2−. The photoelectrochemical cell performance of CZTSSe film photoelectrode was investigated using simple two-electrode system. In dark condition, J–V measurement demonstrates semiconductor behavior and under illumination shows generation of photocurrent of 3.64 mA/cm2 at a photovoltage of 400 mV. The CZTSSe films show photoconversion efficiency (η) of 3.41%, indicating that the hydrothermally grown CZTSSe photocathode is a promising material for film solar cell technology. Electron impedance spectroscopy illustrated generation of charge transport resistance of 465 Ω.