Effects of compression and controlled selenization on powder-fabricated Cu (In,Ga)Se2 thin films

Cu(In,Ga)Se-2 thin films have been used as a light absorbing layer in high-efficiency solar cells. Among many methods, the powder process for fabricating Cu(In,Ga)Se-2 thin films is advantageous, due to its simplicity and minimal usage of materials. However, Cu(In,Ga)Se-2 layers produced by the powder process often result in high porosity and small grain sizes, which has been a significant barrier to wide application. In this report, we demonstrate that simple compression of the Cu(In,Ga)S-2 powder coat and a cost-efficient selenization using a mixture of Se and Al2O3 can reduce porosity and enlarge the grain size. It is surmised that improved particle packing density in the powder coats, in addition to sintering with a steady supply of Se vapor, synergistically enhances highly sintered Cu(In,Ga)Se-2 thin films.