Researchers at the Leibniz Institute for New Materials (INM) have developed a barrier layer for flexible CIGS solar cells which separates the metal substrate from the absorber layer and so increases the efficiency of the metal-based flexible thin-film solar cells. A wet chemistry spray process can then be used to apply it to flexible and rigid substrates with a variety of shapes. This includes new developments for corrosion protection coating and low-friction coating as well as antimicrobial coatings and printed electronics.
The glass-like layer increases the efficiency of the solar cells in a different way. “It acts as an iron diffusion barrier, preventing the unwanted penetration of iron ions into the absorber layer. Exactly that would lead to the loss of the efficiency”, explains Peter William de Oliveira, Head of the Optical Materials Program Division. “At the same time, the barrier works as an insulating layer and reduces unwanted electrical currents from the absorber to the substrate”, he adds. In addition, the coating is a source for the doping element sodium which increases the efficiency of flexible, metal-based CIGS thin-film solar cells to 13%. The new barrier layer also makes it possible to monolithically connect several cells on one and the same substrate to modules.
The glass-like diffusion barrier is applied to the metal substrate using the sol-gel process. It is transparent, flexible and only two to five micrometers thick. Flexible A3-size films can be produced by dip coating and slot coating. For the further upscaling process, researchers at the INM then developed a method with which they can apply the coating via a spray process to large substrates with a variety of shapes. In addition, films up to 50 meters long and 1.5 meters wide can also be coated using classic roll-to-roll processes.