Compact Cu2ZnSn(S,Se)4 Thin Films Fabricated by a Simple Sol-Gel Technique

Cu2ZnSn(S1-xSex)4 (CZTSSe) thin films with a compact and crack-free morphology and large-grain are ob- tained via a green Sol-Gel process and post-selenization. The fabrication of CZTSSe films is simplified by predigest- ing preparation process of Cu2ZnSnS4 (CZTS) precusor solution and avoiding using sulfurization. Low-toxic ethylene glycol is selected as solvent, and Cu(CH3COO)2, Zn(CH3COO)2, SnCl22H2O and thiourea are used as raw materials. Energy dispersive X-ray analyzer (EDX), X-ray diffraction (XRD) and Raman spectra results indicate that all of CZTSSe thin films with the kesterite structure are of Cu-poor and Zn-rich states. Optical band gap (Eopt) of the CZTSSe thin films decreases from 1.51 to 1.14 eV with increasing Se content.