Improvement of Ga distribution with Sb incorporation for two-step low-temperature processing of CIGSe thin film solar cells

In this study, the application of Sb incorporation for low-temperature (<= 450 degrees C) processing of Cu(In,Ga)Se-2 (CIGSe) solar cells is explored. At low reaction temperature, most Ga remains at the back of the film adjacent to the Mo back contact. We observed that the incorporated Sb enhanced grain size and improved device performance compared with similarly processed CIGSe films made without Sb. From the energy-dispersive spectroscopy analysis and secondary ion mass spectrometry results, it was determined that elemental Ga accumulation at the back of the reacted film after the two-step selenization process was significantly alleviated owing to Sb incorporation. Significant Sb-induced grain size enhancement was confirmed using cross-sectional scanning electron microscopy. The electronic and optical properties of the Sb incorporated CIGSe films were examined with admittance spectroscopy and fluorescence lifetime imaging techniques.