Deposition of Cu2ZnSnS4 films by doctor blade printing using a one-step microwave heated ink as an absorber layer for solar cells

Abstract

Kesterite (Cu2ZnSnS4, CZTS) semiconductors are known as the most suitable compounds for the synthesis of absorber layers. These compounds are used in solar cells due to their high solar energy absorption coefficient and ideal band gap. In the present work, the microwave-assisted process and doctor blade printing were used to prepare Cu2ZnSnS4 films. To this aim, ink solution was used, which consisted of copper, zinc acetate, tin chloride and thiourea as copper, zinc, tin and sulfur precursors, respectively. Ethylene glycol was used as a non-toxic solvent. The CZTS ink was prepared using microwave heating for 10 min. The CZTS layers were printed on soda lime silica glass substrates and heat treated at 150, 200, 250, 300, and 350°C. The microstructure, phase analysis, morphology, optical properties, and absorption ratio of the samples were evaluated using X-ray diffraction analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, transmittance spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray, and UV–Vis spectrophotometry. The formation of the Kesterite structure was confirmed using X-ray diffraction and Raman spectroscopy. The FESEM micrographs and DLS (dynamic light scattering) revealed that the films contained equated grains with the diameter range of 350–650 nm. According to the X-ray analysis and Raman spectrum, the highest crystallization and purity of the Kesterite phase as well as the best microstructure property and morphology (smooth spherical particles with good adhesion) of the CZTS films were found in the synthesized specimen at 300°C. The band gap of the samples was measured to be about 1.5 eV using UV–Vis spectrophotometry.