Coating and interconnect development for a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells on polymer substrate for space and stratospheric applications

A top coating has been developed for a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells on polymer substrate for space and stratospheric applications. Several candidate coatings were screened for potential use in the space and stratospheric environments. A proprietary coating performed well; however, the coating exhibited darkening after UV exposure in high vacuum or inert atmosphere. The darkening was reversed with a postexposure treatment. An effective pre-treatment technique has been developed to prevent darkening in UV/vacuum, such as in high-orbit space applications. A method has been developed to interconnect lightweight thin film cells on polymer into strings. Strings have been tested for mechanical robustness and have been repeatedly rolled and unrolled with no degradation in cell performance.