Deposition of Cu2ZnSnS4 (CZTS) prepared by a solution route for solar cells applications
Résumé
As a promising candidate as absorber layer in thin film solar cells, the Cu2ZnSnS4 (CZTS) material has gained a broad interest over recent years for the production of low-cost solar cells due to its direct and tunable band gap energy, high optical absorption coefficients and also due to the abundance and the non-toxicity of all its constituents. In addition, to solve the problem of expensive and complicated vacuum-based synthesis methods, simple and low-cost methods have been developed for the preparation of this material. In this present work, the CZTS thin films have been prepared using a solution route namely sol-gel, which is a simple and low cost method for a large production of thin films materials and spin coated onto glass substrates. The sol-gel precursor solution was made from metal salts of copper (II) chloride (CuCl2), zinc (II) chloride (ZnCl2), Tin (IV) chloride (SnCl4), and thiourea (CS (NH2)2) dissolved into a mixture of ethanol/water as solvent. The X-ray diffraction studies showed the formation of a kesterite structure with peaks corresponding to (112) and (220) directions. The Raman spectrum indicated the presence of the principal kesterite peak at 336 cm-1 and the existence of a strange peak at 424 cm-1 which could be attributed to the binary compound Cu2S. The absorbance spectrum has been recorded for the estimation of the band gap. The CZTS thin film can be made using a simple spin coating technique, but improvements in the film properties by a suitable annealing time and temperature as well as annealing environment and post deposition needs have to be done for making a quality photovoltaic absorber.