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

Abstract 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)Se 2 (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 In 2 S 3, 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 CuInSe 2 grains and the bottom layer with small Cu(In, Ga)Se 2 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/cm 2 and a fill factor of 0.66 with an active area of 0.14 cm 2 .