High-Efficiency Amorphous Solar Cells on Polyimide Web

Thin film photovoltaic 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) have demonstratedvery 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 presently manufactures ultra lightweight amorphous silicon solar cells using apolyimide 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 full focus on developing maximumefficiency 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 monolithic integrated a-Si to a low costspace-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 solely on the issues associated withconverting a low-cost terrestrial PV into a space PV. The primary goal of Phase I is to develop and demonstrate the feasibility of a new deposition process for a back surface reflection enhancing layer on our roll to roll fabricated, polymer baseddevices.In addition to lightweight power for space use, polymer based flexible photovoltaics have significant other DOD uses. These include lightweight portable fold-up or roll-up modules for field communications and modules integrated into tents or othertemporary structures to power communications, lighting and filtering systems. Commercial uses include photovoltaics integrated into building structures for grid and non grid power as well as power for portable electronic devices. Power integrated intoemergency shelters is another use.