Capturing more light for solar cells by ‘taming the physics’
By Ann Steffora Mutschler, Senior Editor -- EDN, October 10, 2007
Oulu, Finland-based optoelectronic materials supplier Braggone today unveiled a materials-based approach to increasing the efficiency of solar cells, also aimed at allowing manufacturing facilities to cost-effectively increase their capacity.
Braggone says that incorporating its materials into the manufacturing process can allow the costs of manufacturing solar cells to be dramatically reduced.
The company reminded that the basic building block of solar cells – silicon -- is very shiny and reflects about 30 percent of sunlight back into the sky. Solar companies trap this light by putting down very thin anti-reflective coatings to reduce the reflected light, and to help trap as much photo energy and convert it into as much electricity as possible, the silicon must be either of very high purity or have very few defects, Braggone explained.
Over the years, the company said, the conversion process has been accomplished by introducing hydrogen into manufacturing, and until now, the anti-reflective and hydrogenation for advanced cells has been done with a chemical vapor deposition (CVD) process.
Dr. Yrjö Ojasaar, CEO of Braggone noted that the optical and electrical layers were previously integrated into components through expensive and high maintenance CVD tools but that the company can now introduce the same anti-reflective and hydrogenation techniques with a simple and cost efficient spray coat, bake and repeat process.
"We are tuning the optics of the cell by introducing nanometer-thick layers of our molecularly tailored materials. Now, for the first time, solar cell makers can have truly affordable passivation and anti-reflective solutions available and thus create a boost for their megawatt production capacities,” he explained in a statement.
Braggone maintains its process is a very low cost barrier to entry for newly constructed solar cell factories, whereas existing lines that already include CVD tools can increase their capacity with low capital investment costs.
Older factories that do not use anti-reflectives can simply increase the efficiency of their output cells and modules by introducing this process at low investment costs.
The material is spray coated on to the solar cell, or glass, then cured at an elevated temperature, marking a breakthrough not only for crystalline silicon makers, but also for use in thin film photovoltaics and in solar module manufacturing to further improve power output.
The company says it is essentially minimizing the optical loss in solar cells and modules and capturing as much light as possible in the cells by taming the physics.
Braggone says with the new materials, it is possible to reduce optical loss in the cell or module, as well as improve the efficiency of electrical conversion within the cell, which has the real benefit of driving down production cost per megawatt output.
More specifically, the company’s material technology allows a flexible modification of the inorganic-organic polymer material properties to suit specific applications. These flexible yet stable materials coat or print onto substrates at greater efficiency, lower temperatures and higher yields.
Finally, the company said its materials have been applied in digital displays for mobile phones and televisions, advanced semiconductors digital cameras, photovoltaic panels, and memory for PCs and MP3 devices.
