High Efficiency Amorphous Solar Cells on Polyimide Web

"Thin film photovoltaic (PV) modules fabricated on polymer substrates have a number of very attractive features for space use. Flexible a-Si modules: 1) have shown minimum degradation due to radiation; 2) can have low fabrication costs; 3) havedemonstrated very high power to weight ratios; 4) have high tolerance to vibration and shock; 5) can be monolithically integrated to give very flexible design options. Iowa Thin Film Technologies (ITFT) presently manufactures ultra lightweight amorphoussilicon solar cells using a polyimide web substrate for the terrestrial market. Typical efficiency for the terrestrial product is approximately 5%. Finished solar cells of this type are presently capable of a specific power of 750 W/Kg. With a fullfocus on developing maximum efficiency for space use, laboratory results indicate that efficiency could approach 10%. Under this effort, ITFT proposes a systematic program to transition our existing production-based terrestrial flexible monolithicintegrated a-Si to a low cost space-rated PV. Since ITFT has already developed the core manufacturing processes of depositing on a flexible polymeric substrate and monolithic integration, we are in the unique position of being able to concentrate solelyon the issues associated with converting a low-cost terrestrial PV into a space PV. In Phase I we demonstrated the feasibility of depositing a back surface reflection enhancing layer on our roll to rol