Cu(In,Ga)Se₂ thin-film solar cells based on a simple sputtered alloy precursor and a low-cost selenization step

High-efficiency thin-film solar cells based on Cu(In,Ga)Se2 are often formed by depositing precursor films and using a subsequent selenization step. We demonstrate a simple and cost-efficient approach simplifying both process steps by using a ternary Cu-In-Ga alloy target for sputter deposition of the precursor layer and by using a simple nonvacuum selenization reaction based on elemental selenium. In this contribution we examine in detail the characteristics of the precursor layers. The sputter growth is governed by a segregation of In-rich islands on top of a closed Cu-rich base. With optimized layers we could achieve conversion efficiencies well above 13% without the use of antireflective coating or metallic grids. The influence of the selenization duration on morphology and performance is discussed.