Thermal treatments and characterization of CZTS thin films deposited using nanoparticle ink

Abstract

The structural, optical, and optoelectronic properties of copper zinc tin sulfide (CZTS) films, deposited by a nonvacuum nanoparticle based approach were studied as a function of different annealing temperatures. The CZTS films for photovoltaic applications were deposited using the doctor blading method using an ink prepared with nanoparticles synthesized using the solvothermal method. Deposited films were annealed at different temperatures in N2–S atmosphere. The films were characterized using different tools such as X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), ultraviolet–visible spectroscopy, Raman spectroscopy, and photoconductivity. The results showed that the kesterite phase was formed in the temperature range between 400 and 550 °C. At temperatures beyond 500 °C, many peaks of binary and ternary phases were detected, probably because of the decomposition of the kesterite layer. The cross section SEM images showed that the film is compact; however, there are isolated voids. The EDXS estimated chemical composition was found to vary with annealing temperature; the nearly stoichiometric film was obtained when annealed at 450 °C. The optical band gap of the stoichiometric film was 1.6 eV, and it showed photoconductivity.