Researchers at Massachusetts Institute of Technology (MIT) have developed a new online tool for optimizing materials and production for solar cells.
Assistant Professor of Mechanical Engineering Tonio Buonassisi. Photo: Patrick Gillooly
“Impurities to Efficiency” (I2E), the online tool, allows researchers and manufacturers who are studying alternative methods of manufacturing solar cells to enter details about the materials and processing steps that they have planned. The tool simulates the process and then provides an indication of the conversion efficiency of the solar cell.
Tonio Buonassisi, an assistant professor of mechanical engineering at MIT led the research team comprising graduate students David Fenning and Douglas Powell and other partners at the Solar Energy Institute in Technical University of Madrid, Spain.
Highly purified silicon crystal is used to manufacture silicon solar cells. A crystal slice is processed through multiple stages that involve heating and cooling. The level of purity and the manufacturing process has not been defined and has been varying. The duration, fastness and how to heat or cool the crystal slice has been a trial and error process. The I2E tool helps address these issues.
Silicon used in solar cell production has a purity of 99.9999%. The remaining impurity of iron is a major obstacle to flow of electrons. The size and amount of iron and also its distribution plays a major role. These factors are difficult to predict and measure. The tool helps tackle these factors.
The research team utilized basic physics and computer simulation to predict the behavior of iron atoms during the silicon wafer-manufacturing process. An X-ray beam from Argonne National Laboratory’s synchrotron was used to reveal the actual iron particle distribution in the silicon wafers. The simulation was compared and confirmed with the synchrotron’s results.
Varian Semiconductor Equipment Associates utilized I2E and improved the efficiency and speed of producing silicon wafers.
Research centers from all over the globe have utilized the free I2E website, which has provided around 2000 simulations since July. Trade journal Photovoltaics International will publish the details of the tool.