Monolithically integrated flexible Cu(In,Ga)Se2 solar cells and submodules using newly developed structure metal foil substrate with a dielectric layer

Monolithically integrated Cu(InxGa1−x)Se2 (CIGS) submodules having a certified efficiency of as high as 15.9% (16 cells, a designated area of 69.6 cm2) were successfully fabricated on flexible substrates with a newly developed structure. This proved not only to achieve high efficiencies, but also to enable implementation of a low-cost manufacturing technique: roll-to-roll processing and monolithical integration. The newly developed substrates have a laminated structure with an Al2O3 dielectric layer formed by anodization on stainless steel, and satisfy the crucial requirements for manufacturing flexible CIGS submodules, including thermal stability over 500 °C, a well-matched coefficient of thermal expansion for CIGS, an absence of impurities in the CIGS, sufficient dielectric properties, flexibility for roll-to-roll processing, low weight, and low material costs. Therefore, fabrication of modules on this flexible substrate offers the following attractive merits: high efficiency, low cost, and easy installation. Until now, no flexible substrates have satisfied these requirements all at once, our substrate is the most promising candidate for attractive flexible CIGS modules instead of conventional rigid CIGS modules.