Ambient CdCl2 treatment on CdS buffer layer for improved performance of Sb2Se3 thin film photovoltaics

Antimony selenide (Sb2Se3) is appealing as a promising light absorber because of its intrinsically benign grain boundaries, suitable band gap (similar to 1.1 eV), strong absorption coefficient, and relatively environmentally friendly constituents. Recently, we achieved a certified 5.6% efficiency Sb2Se3 thin film solar cell with the assistance of ambient CdCl2 treatment on the CdS buffer layer. Here, we focused on investigating the underlying mechanism from a combined materials and device physics perspective applying current density-voltage (J-V) fitting analysis, atomic force microscope, X-ray photoelectron spectroscopy, fluorescence, and UV-Vis transmission spectroscopy. Our results indicated that ambient CdCl2 treatment on CdS film not only improved CdS grain size and quality, but also incorporated Cl and more O into the film, both of which can significantly improve the heterojunction quality and device performance of CdS/Sb2Se3 solar cells. (C) 2015 AIP Publishing LLC.