High efficiency thin-film Cu(In,Ga)Se2-based photovoltaic devices: progress towards a universal approach to absorber fabrication

The formation chemistry of Cu(In,Ga)Se₂ by several reaction paths has been considered, and growth models of these processes have been developed. The results suggest a simple, reproducible approach to the formation of the multinary compound. The foundation of a universal process for the fabrication of Cu(In,Ga)Se₂-based solar cells is presented. Several embodiments of the process make it self-limiting with moderate compositional tolerances and simple endpoint detection. It is applicable to different device structures, and scalable to a variety of hybrid deposition technologies. A growth model is presented that correctly describes this process and related ones. Novel CuInSe₂ single-layer and Cu(In,Ga)Se₂/CuGaSe₂ multilayer absorber structures have been fabricated by physical vapor deposition using this process. Laboratory-scale photovoltaic devices demonstrate a total-area efficiency of 13.3%