Low-cost Solar through Fast Production
2014 R&D 100 Winner
Crystalline silicon has continued to lead the market in the worldwide adoption of solar energy with over 85% market share. Much of this growth has happened in the past few years. Photovoltaic modules have dropped in price to below $1/W due to massive vertical integration largely driven by Chinese manufacturers.
However, the cost to manufacture panels has not scaled down, resulting in losses for manufacturers. Crystal Solar Inc.’s Direct Gas to Wafer Epitaxial System, developed with the National Renewable Energy Laboratory, is designed to help reduce these costs by increasing throughput. Each mini-batch of wafers is vertically loaded in the reactor in a configuration where the substrate wafers are held in silicon-carbide sleeves facing each other. The spacing between the wafers has been optimized to achieve maximum average growth rate when the sleeves are heated and reactant gases—hydrogen (H2) and trichlorosilane (TCS)—flow between them. The kerfless system operates in a TCS-depleted regime, which allows greater than 40% TCD conversion efficiency, more than 10 times better than conventional reactors. A high growth rate of more than 4.5 µm/min is enhanced by periodically reversing reactant flow, which boosts uniformity to better than 90%. Finally, 12 of these chambers may be clustered together to achieve a total system throughput of about 320 wafers per hour, increasing throughput to more than 100 times the closest competitor and reducing costs 50%.
Wafer epitaxial system
|Crystal Solar Inc.'s Direct Gas to Wafer Epitaxial System development team (l-r): T.S. Ravi, V. Siva and J. Vatus.|
|National Renewable Laboratory's Direct Gas to Wafer Epitaxial System development team (l-r): Harin Ullal, Steve Johnston and Bhushan Sopori.|
The Direct Gas to Wafer Epitaxial System Development Team
T.S. Ravi, Principal Developer, Crystal Solar Inc.
Harin Ullal, Principal Developer, National Renewable Energy Laboratory