CIGS solar cells on flexible ultra-thin glass substrates: Characterization and bending test

• Cu(In,Ga)Se2 solar cells were fabricated on flexible borosilicate ultra-thin glass.
• Performances were compared to those of cells fabricated on rigid soda-lime glass.
• Cu(In,Ga)Se2 layer properties were investigated notably by quantitative GD-OES.
• Differences are due to a lower Na supply in the case of ultra-thin glass substrates.
• The impact of cell bending on photovoltaic characteristics was studied.

The development of lightweight and flexible photovoltaic devices is highly desirable for integration in new applications and to reduce the manufacturing cost of modules. In this context, a lot of effort is put into the development of Cu(In,Ga)Se2 (CIGS) based solar cells on flexible substrates as alternatives to the standard soda-lime glass substrates. Flexible metallic and polyimide foils are frequently used, but in this work we investigated another substrate material presenting advantageous properties: flexible ultra-thin glass. In this article we demonstrated CIGS solar cells with 11.2% efficiency grown on flexible glass as thin as 100 μm. It was shown that the differences between solar cells fabricated on ultra-thin glass and standard cells fabricated on 1-mm-thick soda-lime glass lie in the lower Na supply in the first case. We also studied the evolution of solar cell performances when they are bent. This last point is rarely discussed in studies on CIGS on flexible substrates in spite of its importance for flexible device applications.