2010 R&D 100 Winner
In solar cells that absorb sunlight, any photons reflected from the cell surface can’t be converted to electricity. Conventional photovoltaics (PV) absorb between 93% and 95% of solar radiation, the remainder is reflected away. To reduce waste from reflection and increase cell efficiency, National Renewable Energy Laboratory (NREL), Boulder, Colo., scientists have invented the Black Silicon Nanocatalytic Wet-Chemical Etch, a process that turns silicon wafers black so they absorb 98% of solar radiation.
The one-step, wet-chemical etch process changes the standard PV process of etching the silicon then applying anti-reflective coatings. In NREL’s method, the etch is catalyzed by gold nanoparticles and completed by an acid and peroxide solution, leaving a network of nanoscale cylinders or voids that reduce reflectance, boosting final cell performance by 2.9%. The etch requires less than three minutes at room temperature—and less than one minute at 40°C.
Avoiding the antireflective coating step saves manufacturing costs of $0.021 to $0.028 per watt, a 16% reduction in cell-line expenditures. Etching chemicals for this process are inexpensive, and the gold residuals are easily recyclable. In addition, the non-vacuum process can boost overall PV performance more than 2% and reduce overall cost of energy from silicon solar cells.
Technology
Photovoltaic etching process
Developer
National Renewable Energy Laboratory
Development Team
|
| Front row (l-r): Anna Duda, Howard Branz, Vern Yost. Back row: Matt Page, Scott Ward, and Hao-Chih Yuan. |
The Black Silicon Nanocatalytic Wet-Chemical Etch Development Team from National Renewable Energy Laboratory (NREL):
Howard Branz
Anna Duda
Don Gwinner
Matthew R. Page
Janice Rooney
Scott Ward
Vernon E. Yost
Hao-Chih Yuan
