Investigation of photocatalytic activity (under visible light) of ultrathin CZTS films produced in different thicknesses by PLD method

Abstract

Cu2ZnSnS4 (CZTS) thin films in 61 nm, 112 nm, 242 nm and 313 nm thickness which have been produced by Pulsed Laser Deposition (PLD) on Soda Lime Glass substrates as a function of the number of laser pulses. As the deposition of ablated material has been augmented with increasing number of laser pulses, it has been noticed that CZTS-ultrathin film’s thicknesses and particle sizes have been increased, their crystalline structures have been improved. Larger particles limit the transmission of light and cause thin films to absorb photons. The band gaps of CZTS (61 nm), CZTS (112 nm), CZTS (242 nm) and CZTS (313 nm) thin film which have been determined to be 1.95 eV, 1.90 eV, 1.50 eV and 1.45 eV, respectively. CZTS (61 nm) ultrathin film with the thinnest one among the thin films produced in this work, which is Cu and S poor but Sn and Zn rich. By increasing the thickness of the film, it has been observed that the amount of Cu and S were increased, and the ratio of Sn and Zn were decreased. In addition, it has been systematically investigated that the photocatalytic activity of the ultra-thin CZTS films coated in different thicknesses by PLD method. Among all the photocatalysts, the CZTS (in 242 nm thickness) photocatalyst has exhibited the highest photocatalytic performance, managing to remove 96.1% of methylene blue (MB) in 240 min. Furthermore, the mechanism that performs photocatalysis has been investigated by scavenger experiments, and it was observed that \({}^{ \cdot }O_{2}^{ - }\) radical ions have an important role in the reaction, while holes have little effect.