Ultrahigh Rate Fabrication of Thin Film Silicon Solar Cells Using Roll-to-Roll Hybrid CVD Technologies with RTSE Monitoring and Control
Develop a novel hybrid chemical vapor deposition (H-CVD) process for the roll-to-roll fabrication of high-efficiency thin film silicon solar cells at ultrahigh rates up to 100 angstroms per second.
Sponsor: Xunlight Corporation3145 Nebraska Avenue
Toledo, OH 43607
Radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) has been traditionally used for years to apply layers of amorphous silicon (a-Si) thin films during the manufacture of photovoltaic (PV) solar cells. The method has been plagued by numerous disadvantages: low deposition rates (approximately 2 angstroms per second); the need for large-sized production equipment; and high production costs. Another deposition method, hot wire chemical vapor deposition (HWCVD), has been shown to produce deposition rates up to 100 angstroms per second but yields poor quality layers. Xunlight has proposed a novel H-CVD process that will integrate the speed advantages of HWCD with the quality advantages of PECVD for roll-to-roll fabrication of high-efficiency nanocrystalline silicon thin films for solar cells. The process will be guided by real-time spectroscopic ellipsometry (RTSE) through the use of phase diagrams. Replacing a time consuming trial-and-error method, these diagrams enable a rational approach to the optimization of the complex CVD process required for highest solar cell performance. RTSE also will be implemented for the first time in roll-to-roll solar cell production for simultaneous control of quality and uniformity of the semiconductor material across the manufacturing web. The overall effort is projected to yield a 10-fold reduction in the cost of thin-film deposition equipment. This cost reduction could provide great benefit toward the adoption of renewable energy nationally and globally.