Ultrathin Cu(In,Ga)Se2 based solar cells

The benefits of reducing the thickness of the Cu(In,Ga)Se2 absorber (CIGS) in thin film solar cells outweighs the reduced material costs and production time. It also lowers the minimum quality requirements for the CIGS layer since shorter pathways for electron extraction allow shorter electron diffusion length. However, the design of ultrathin solar cells raises specific issues in terms of absorber quality, light management, and electronic transport. The aim of this paper is to give an overview of the state of the art on ultrathin CIGS solar cells and to present some results and perspectives for the improvement of the opto-electronic properties of ultra-thin solar cells. The impact of the deposition techniques for CIGS such as coevaporation, reactive sputtering and electrodeposition on the properties of ultrathin absorbers will be discussed. Then the potential of replacing the molybdenum back contact by a Transparent Conducting Oxide or a metallic or nanostructured reflectors will be analysed.