Influence of Substrate Temperature and Sulfurization on Sputtered Cu2SnGe(S,Se)3Thin Films for Solar Cell Application

Abstract

This work presents the influence of substrate temperature (Tsub) and post-sulfurization on compositional, structural, electrical, and optical properties of dual-ion beam sputtering (DIBS)-grown Cu2(Sn,Ge)(S,Se)3 (CTGSSe) thin films grown on a soda-lime glass (SLG) substrate using a single target. Post-sulfurization of CTGSSe thin films is carried out in a quartz tube chemical vapor deposition (CVD) system. X-ray diffraction (XRD) analysis reveals that the crystal structure of CTGSSe thin films is preferentially tetragonal with (112) and (204) lattice planes at 2θ values of 27.3° and 47.3°, respectively. Field-emission scanning electron microscopy (SEM) has emphasized that the high Tsubgrowth resulted in a larger grain size of 87 nm and better thin-film morphology. Spectroscopic ellipsometry (SE) analysis shows the bandgap values of 1.46-1.62 eV by varying Tsub from room temperature (RT) to 300 °C. Furthermore, the bandgap widens from 1.56 to 1.64 eV in the CTGSSe thin films due to post-sulfurization. © 1963-2012 IEEE.