Flexible Cd-free Cu(In, Ga)Se2 solar cells with non-vacuum process

Non-vacuum processing combining with roll-to-roll manufacturing technology is available to fabricate large-area and low-cost flexible thin film solar cell. In this work, Cu(In, Ga)Se2 (CIGS) solar cells were fabricated on flexible stainless steel substrates with the CIGS absorber layer prepared using ink-printing technique and selenization process. A Cr diffusion barrier layer was sputtered onto the substrate before the deposition of Mo back contact to prevent the diffusion of detrimental elements like Fe from the substrate. The Cd-free buffer layer of In2S3, instead of the traditional CdS, was deposited on the surface of CIGS absorber layer for non-toxic and environmentally friendly consideration. The CIGS absorber layer exhibits a bilayer structure with the upper layer with large CuInSe2 grains and the bottom layer with small Cu(In, Ga)Se2 grains. The best performance of flexible CIGS solar cell achieves to an efficiency of 11.1%, a Voc of 0.45 V, a Jsc of 37.7 mA/cm2 and a fill factor of 0.66 with an active area of 0.14 cm2.