Recent research conducted at Natcore Technology has revealed uses of its liquid phase deposition (LPD) process in making black silicon solar cells surface more passive.
The silicon wafer surface looks dark after being etched with nano-pores. The etching process occurs within minutes in a liquid at room temperature. The surface looks dark because light is not reflected from the porous surface. Black silicon solar cells could enhance the cell performance.
The polished surface reflects about 40% of light making the wafer shine. An antireflective coating further lowers the reflective capacity to almost 6% making the cells appear dark blue in color. The research conducted jointly by Natcore, the Barron Group funded by Natcore at Rice University, and scientists at the National Renewable Energy Laboratory (NREL) could lower the reflectivity to below 1.5%.
An enhanced area of silicon on the side walls of the pores and the on the nano mesas left on top of the wafer do not allow the enhanced light absorption in a solar cell to yield more power. The enhanced surface must either be made passive or treated to stop it from capturing the electric charges produced by the solar light as they move in the direction of the solar cell, since that could prevent the cell from yielding power.
Professor Andrew Barron's group collaborated with Natcore scientists at the Ohio State University to increase the minority carrier lifespan for the LPD-coated black silicon. The National Renewable Energy Laboratory (NREL) research says this discovery could allow for increased power yield. Filling the suspended atomic ties at the solar cell surface and minimizing flaws in the top part is called passivation. It allows manufacture of long-lasting silicon solar cells.
Chuck Provini, Natcore president and chief executive officer, says the LPD process could passivate black silicon making thermal oxidation unnecessary. An all-liquid phase procedure could help develop ultralow reflective silicon solar cells in bulk quantities, thus lowering overall costs.
Source: http://www.natcoresolar.com