INFLUENCE OF HEATING RATE ON THE STRUCTURAL AND OPTICAL PROPERTIES OF SILVER AND GERMANIUM CO-DOPED CZTS THIN FILM

Abstract

The effect of heating rate on the structural and optical properties of Ag+Ge co-doped CZTS thin film were investigated and compared with the undoped CZTS sample. The undoped and Ag+Ge co-doped CZTS samples obtained by two-stage technique consisting of the sequential deposition of the precursor stacks by sputtering systemand sulfurization of these layers at elevated temperature in the RTP system by employing heating rate of 1°C/s, 2°C/s and 3°C/s. Ag and Ge co-doped precursor stack as well as undoped stack demonstrated Cu-poor, Zn-rich composition. In addition, the dopant ratio of the Ag+Ge co-doped stack was close to the targeted content considering to EDS measurement. Regardless of the employed heating rate or the doping process, all of the samples crystallized in a kesterite structure. However, it was confirmed by XRD measurements that high heating rates caused phase separation in kesterite phase formation. On the other hand, The Raman peaks assigned to Cu-vacancy and CuZn antisite defects formation inhibited with incorporating Ag and Ge into the CZTS structure. Ag and Ge co-doped CZTS sample produced with a heating ramp rate of 1°C/s showed better structural and optical results among them.