Synthesis and Crystallization of CuIn1-xGaxSe2 Compounds Formed via Co-Sputtering with Se Vapor

Abstract

Cu(In,Ga)Se-2 (CIGS) thin films (2.5 mu m thick) were prepared via a two-stage process. First, CuInGa (CIG) precursor films were prepared from a CuGa (7: 3) alloy and an first, CuInGa precursor films were prepared from the CuGa (7: 3) alloy and the In single target by co-sputtering. To control the CIG chemical composition ratio, weights of the Cu, Ga, and In atoms were estimated in the CuGa and In films, respectively. The samples were selenized in a two-zone furnace at 550 degrees C for 90 mins under Se vapor, developed at 330 degrees C using N-2 carrier gas, followed by heating at 600 degrees C for 30 mins. Grain sizes of the CIGS film obtained via selenization of the CuInGa precursor film became larger and smoother than that of the CuInGa precursor. The single phase exhibited high efficiency, whereas cells with multiphase layers exhibited low efficiency. The open-circuit voltage, short-circuit current density, fill factor, and photoconversion efficiency values of the best performing CIGS solar cells were: 0.552 V, 27.8 mA/cm(2,) 51.2%, and 7.84% from CIGS absorbers via selenization at 550 degrees C on a CuInGa precursor (CuGa 50 W, In 52 W).