Influence of carrier gas pressure on the characteristics of nebulizer-sprayed Cu₂ZnSnS₄ absorber thin films

The current work reports the synthesis of the Earth-abundant Copper Zinc Tin Sulfide (CZTS) absorber thin films at low temperature through modified spray pyrolysis technique without high-temperature annealing. The impact of carrier gas pressure during the synthesis of this potential solar absorbing material in the form of thin film is studied within the range of 0.10 to 0.20 Pa at a substrate temperature of 350˚C to understand the variation in its inherent characteristics. The deposited films were analyzed subsequently using X-ray diffraction, Raman spectroscopy, Scanning electron microscopy, Energy dispersive X-ray spectroscopy, Atomic force microscopy, and a UV–Vis spectrophotometer. The influence of the carrier gas pressure on the electrical property of the deposited films is also studied by analyzing its I–V characteristics. Structural and morphological analysis exhibits the formation of highly crystalline CZTS absorber film with good adherence on SLG substrate. The Raman analysis establishes the kesterite structure and the phase purity in the grown CZTS films except 0.15 Pa sample which shows the presence of a trace of Cu₂S binary phase. The grain size as well as roughness of the deposited films is observed to increase with the gas pressure up to 0.15 Pa and decreased thereafter. The band gap of the film is found to decrease from 1.42 to 1.30 eV under the testing limits. The I–V characteristics of the deposited film at 0.15 Pa show higher current value than the rest of the samples. Apart from the study of influence of carrier gas pressure, this study also confirms the usage of the modified nebulizer-assisted spray pyrolysis technique as one of the economical fabrication methods for mass production of nontoxic CZTS absorber thin films that can be used in the development of environment-friendly low-cost solar cells.