Passivating and transparent selective contact for Cu(In,Ga)(Se,S)2 solar cells – PASTEL

CuInGaSe2 solar cells are expected to reach a global market of $8.5 billion by 2024. The state of art solar cell features a 23.4% efficiency using a 2.5µm absorber grown on Molybdenum (Mo). Increasing the efficiency and reducing the absorber thickness (fabrication throughput bottleneck) are the current priorities for industry. Major improvements are expected by replacing the Mo back contact with a more suited one. In the PASTEL project, we propose to develop a novel passivated and transparent selective back contact based on metal oxides and compatible with industrial fabrication processes. Our preliminary results show the compatibility of this approach with a highly reflective back mirror. We target (1) a 20% ultrathin (=400 nm) CuInGaSe2 solar cell, (2) a 10% semi-transparent CuInGaSe2 solar cell, and (3) as a preliminary step towards a Si based tandem, a 15% wide-bandgap CuInGaS2 solar cell directly grown on Si via this novel passivated and transparent selective contact.