Ultra-Lightweight Photovoltaic Cells on Flexible Substrtaes for Energy Conversion Applications

Portable devices that can generate electricity from solar power are very attractive for many defense applications, in particular for mobile defence units. Light and durable solar cell panels would greatly simplify the logistics of military operations, such as by eliminating heavy and cumbersome electricity generators and personal battery packs. Advances in amorphous silicon (a-Si) deposition and patterning have led to the development of ultra-light thin-film photovoltaic cells that can be rolled up for efficient storage. The main drawback of currently available devices is the low intrinsic mobility of a-Si, which leads to lower energy conversion efficiency. These drawbacks have thus far prevented thin-film photovoltaic cells from displacing the heavier and more rigid conventional solar cell devices that are based on single-crystal Silicon (c-Si). Standard methods for crystallizing a-Si require high temperatures that are incompatible with thin-film materials, which are often polymeric in nature. One of the most promising techniques for crystallizing silicon on flexible substrates is excimer laser crystallization, which involves using short pulses of ultraviolet (UV) emission from an excimer laser to locally heat a small area of an a-Si substrate. By scanning the laser beam in an appropriate manner over the entire substrate, large areas of single-crystal silicon can be formed. We propose to use our capabilities in excimer laser crystallization as well as our expertise in high-throughput lithography and direct batch photoablation to develop efficient, large-area, lightweight, thin-film photovoltaic devices.