Increasing U.S. Market Share in Solar Photovoltaic Manufacturing
From 2000 to 2010, global shipments of solar cells and modules grew 53%, a wave that China and Taiwan rode to increase their combined market share from less than 2% to 54%. Meanwhile, U.S. market share slipped from 30% to 7%. Cutting-edge manufacturing and reduced costs can help the United States regain its share of the solar photovoltaic market.
As solar cells move through the production line, they must be oxidized, annealed, purified, diffused, etched, and layered. Heat is indispensable for each step, and that's why manufacturers use large furnaces. Until now, the state of the art has been furnaces that use radiant or infrared heat to quickly boost the temperature of silicon wafers.
In contrast, NREL's Optical Cavity Furnace (OCF) uses only light, enclosing an array of lamps within a highly reflective chamber to achieve an unprecedented level of temperature uniformity. The OCF operates efficiently, gives manufacturers more control, and can help produce more efficient solar cells. It can also save money by eliminating mechanically inferior wafers early in the manufacturing process.
As solar cells move through the production line, they must be oxidized, annealed, purified, diffused, etched, and layered. Heat is indispensable for each step, and that's why manufacturers use large furnaces. Until now, the state of the art has been furnaces that use radiant or infrared heat to quickly boost the temperature of silicon wafers.
In contrast, NREL's Optical Cavity Furnace (OCF) uses only light, enclosing an array of lamps within a highly reflective chamber to achieve an unprecedented level of temperature uniformity. The OCF operates efficiently, gives manufacturers more control, and can help produce more efficient solar cells.
Black Silicon Absorbs More Light
Solar cells work best when they absorb sunlight rather than reflect it. To that end, NREL developed an etching process that quickly turns silicon black. The efficiency gains of this process, combined with savings from not applying conventional antireflection coatings, are expected to cut solar costs by $5–$10 per module.
NREL's etching bath, shown in the photograph, quickly turns silicon black.
Researchers at NREL invented a solid-state optical system that measures solar cell quantum efficiency (QE) in less than a second. QE is a measurement of how cells respond to light across the solar spectrum, but traditional methods for measuring QE were too slow. NREL's technique was licensed and further developed by Tau Science Corporation as FlashQE using light-emitting diodes, high-speed electronics, and mathematical algorithms to measure the QE of a solar cell up to 1,000 times faster than previously done and allowing its use on every solar cell passing through a production line.
Shooting for the Sun
NREL supports the Energy Department's SunShot initiative, which seeks to make solar energy cost-competitive with other forms of electricity by 2020. The first awards under the initiative went toward further developing U.S. manufacturing supply chains. At the same time, NREL invested $7 million in its successful PV Incubator program, which helps to shorten the commercialization timeline for promising emerging solar technologies.
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