Pulsed potential co-electrodeposition of Cu₂CoSnS₄ absorber layer on fluorinated tin oxide (FTO)-coated glass

Thin films of Cu₂CoSnS₄ (CCTS) are electrodeposited onto fluorine tin oxide substrate using pulsed electrodeposition mode for various time periods followed by sulfurization treatment at 500 °C. The pulse potential (V1) is held constant at 0 V vs. Ag/AgCl, while (V2) is set at − 1.1 V vs. Ag/AgCl. The effect of pulse duration on the CCTS proprietress is being investigated. Cyclic voltammetry was used to study the electrochemical behaviors of Cu–Co–Sn–S precursors, while in situ electrochemical impedance spectroscopy investigated the electrical properties of the system during electrodeposition of CCTS at − 1.10 V. The impedance spectra revealed a capacitive loop pattern along with Warburg diffusion. The samples were analyzed by X-ray diffraction (XRD), Raman spectroscopy, and UV–visible spectroscopy. Both XRD data and Raman spectra indicated that the CCTS thin films have a stannite structure. The films deposited for 20 min and 30 min exhibit a predominantly pure CCTS phase. Moreover, deposition for 20 min exhibits a homogeneous morphology with a nearly stoichiometric composition along with an optical band gap energy of 1.54 eV. Apart from the CCTS phase, noticeable secondary phases are present in films deposited at both low and high pulse durations, and they have been observed to slightly affect the gap energy.