Surface recombination is a critical parameter that determines the perfromance of thin silicon solar cells. We have developed a passivation process with very low recomination giving very high minority lifetimes in crystalline silicon exceeding 60 ms.
The paper is publlished online at Applied Physics Letters: ]S. Y. Herasimenka, C. J. Tracy, V. Sharma, N. Vulic, W. J. Dauksher, and S. G. Bowden, “Surface passivation of n-type c-Si wafers by a-Si/SiO2/SiNx stack with <1 cm/s effective surface recombination velocity,” Applied Physics Letters, vol. 103, no. 18, p. 183903, Oct. 2013..
At the solar power labs we have opportunities for students starting in Spring 2014. There are Engineering Dean's felllowships available for US Citizens with good grades. For more details on the Dean's fellowships please see the link:
Vivek Sharma is our most recent graduate. He successfully defended his PhD thesis in September, 2013 on the "Study of Chrages Present in SIlicon Nitride Films" During his PhD he demonstrated the ability of silicon nitride to hold both positive and negative charge and to hold that charge over extended periods. The work has important implications for advanced silicon solar cells where recombination at the surfaces is increasingly important and there is a wide range in electronic doping and type.
We are pleased that Vivek was hired by Intel even before graduation. He is presently traveling to Hillsboro Oregan and will work on advanced chip design.
A recent publication in Applied Physics Letters published a result showing a solar cell with an open circuit voltage of 753 mV. To date this is the highest published value of an open circuit voltage in a silicon solar device.
The article citation is:
S. Y. Herasimenka, W. J. Dauksher, and S. G. Bowden, “>750 mV open circuit voltage measured on 50 μm thick silicon heterojunction solar cell,” Applied Physics Letters, vol. 103, no. 5, pp. 053511–053511–4, Aug. 2013.
The direct link to the article is: http://link.aip.org/link/?APL/103/053511&aemail=author
The solar power lab is now powered by solar! The solarization project at ASU continues to expand with the latest addition being 1 MW of capacity covering the building and parking lot of MacroTechnologyWorks, which is the building that houses the Solar Power Labs. The system provides more than enough power to offset the usage of the solar power lab. As a grid tied system, the extra power on sunny days is fed back into the grid. An additional benefit of the system is that it provides shading for over 200 cars, which is a welcome relief during the hot Phoenix summer where temperatures regularly exceed 115 F.
More information is available at https://cfo.asu.edu/solar-installations
The Solar Power Laboratory runs undergraduate research projects, many of which are provided by the Fulton Undergraduate Research Initiative (FURI). Read more about the experiences of a recent undergraduate researcher here.
Natasa Vulic is helping improve the efficiency of solar cells to meet future energy demand. She began her research in ASU’s Solar Power Lab as an ASU undergraduate in the Barrett Honors College and is continuing as a graduate student. Her outlet from all that mental work is running up to 90 miles per week as a Sun Devil athlete on the cross-country team.
Arizona State University takes full advantage of being in the "Valley of the Sun" and has an agressive program to install photovoltaic generating systems with more installed PV capacity than any other university in the United States. The installations are starting to pay real dividends. On February 24 half the power used on campus in the middle of the day was provided by photovoltaic systems.
Twelve students just finished the latest course on the manufacture of solar cells at ASU. At the completion of the course the students were able to complete the manufacture of high efficiency solar cells on the pilot line at the solar power labs. Half the students came from across the US as part of the QESST engineering research center, and the other half were from the SUN IGERT program at ASU.
The performance of a solar cell depends on the intrinsically on the parameters of the junction. The goal of the class is to expand the understanding and analysis of junctions from the relatively ideal cases typically considered to include advanced concepts and approaches. The goals of the class are to first analyze pn junctions and include non-idealities such as surface recombination; injection-level or doping-dependence; and material parameters which are time, spatially or temperature dependent. The class then covers advanced topics in junctions, such as multi-junctions and the tunnel junctions between them; the physics of heterojunctions; and other junctions such Schottky diodes, Ohmic contacts and MIS approaches. Finally, the course examines new concepts in junction theory such as induced junctions, and carrier or energy selective contacts.