New World Record For Efficiency For Solar Cells; Inexpensive To Manufacture
ScienceDaily (May 17, 2008) — Physicist Bram Hoex and colleagues at Eindhoven University of Technology, together with the Fraunhofer Institute in Germany, have improved the efficiency of an important type of solar cell from 21.9 to 23.2 percent (a relative improvement of 6 per cent). This new world record is being presented on Wednesday May 14 at a major solar energy conference in San Diego.
The efficiency improvement is achieved by the use of an ultra-thin aluminum oxide layer at the front of the cell, and it brings a breakthrough in the use of solar energy a step closer.
An improvement of more than 1 per cent (in absolute terms) may at first glance appear modest, but it can enable solar cell manufacturers to greatly increase the performance of their products. This is because higher efficiency is a very effective way of reducing the cost price of solar energy. The costs of applying the thin layer of aluminum oxide are expected to be relatively low. This will mean a significant reduction in the cost of producing solar electricity.
Ultra-thin
Hoex was able to achieve the increase in efficiency by depositing an ultra-thin layer (approximately 30 nanometer) of aluminum oxide on the front of a crystalline silicon solar cell. This layer has an unprecedented high level of built-in negative charges, through which the -- normally significant -- energy losses at the surface are almost entirely eliminated. Of all sunlight falling on these cells, 23.2 per cent is now converted into electrical energy. This was formerly 21.9 per cent, which means a 6 per cent improvement in relative terms.
LINK
See also:
***
New World Record Achieved In Solar Cell Technology
ScienceDaily (Dec. 7, 2006) — U.S. Department of Energy (DOE) Assistant Secretary for Energy Efficiency and Renewable Energy Alexander Karsner has announced that with DOE funding, a concentrator solar cell produced by Boeing-Spectrolab has recently achieved a world-record conversion efficiency of 40.7 percent, establishing a new milestone in sunlight-to-electricity performance. This breakthrough may lead to systems with an installation cost of only $3 per watt, producing electricity at a cost of 8-10 cents per kilowatt-hour, making solar electricity a more cost-competitive and integral part of our nation's energy mix.
"Reaching this milestone heralds a great achievement for the Department of Energy and for solar energy engineering worldwide," Assistant Secretary Karsner said. "We are eager to see this accomplishment translate into the marketplace as soon as possible, which has the potential to help reduce our nation's reliance on imported oil and increase our energy security."
Attaining a 40 percent efficient concentrating solar cell means having another technology pathway for producing cost-effective solar electricity. Almost all of today's solar cell modules do not concentrate sunlight but use only what the sun produces naturally, what researchers call "one sun insolation," which achieves an efficiency of 12 to 18 percent. However, by using an optical concentrator, sunlight intensity can be increased, squeezing more electricity out of a single solar cell.
The 40.7 percent cell was developed using a unique structure called a multi-junction solar cell. This type of cell achieves a higher efficiency by capturing more of the solar spectrum. In a multi-junction cell, individual cells are made of layers, where each layer captures part of the sunlight passing through the cell. This allows the cell to get more energy from the sun's light.
For the past two decades researchers have tried to break the "40 percent efficient" barrier on solar cell devices. In the early 1980s, DOE began researching what are known as "multi-junction gallium arsenide-based solar cell devices," multi-layered solar cells which converted about 16 percent of the sun's available energy into electricity. In 1994, DOE's National Renewable Energy laboratory broke the 30 percent barrier, which attracted interest from the space industry. Most satellites today use these multi-junction cells.
LINK