Featured Reasearcher - Liming Ji

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Liming Ji came to the United States to pursue his PhD. in Electrical Engineering at the University of Arkansas, focusing his research on the area of renewable energy, specifically solar energy.  While solar energy is one of the leading sustainable energy options, it is not yet widely utilized by the general public because of the cost.  “The cost per watt of solar energy is still three times more expensive than fossil fuels,” says Ji.  He went on to say that in order to bring solar energy use into the mainstream and make it available to the general public, we must lower the cost of solar cells.  This is a central goal of the Generating Renewable Energy with Efficient Nanoplasmonic Solar Cells (GREEN) Research Team of which Ji is a part.

The most expensive aspect of solar cell production is the preparation of the semiconductor material, which absorbs light energy and converts it into electrical energy.  This semiconducting material represents 50% of the total cost to produce a solar cell, and because of this many researchers are directing their efforts toward improving this aspect of the cell.  To ensure sufficient energy absorption, conventional solar cells incorporate a thick wafer or mound of semiconductor material resulting in an efficient, yet very expensive solar cell.  Through the development of thin-film solar cells, which use only 1% of conventional semiconductor materials, production cost is now significantly lower.  However, by reducing the size of the semiconductor materials, researchers not only reduced cost, but they limited the efficiency of light absorption.  Herein lies the cusp of Liming’s research:  to improve light absorption of thin-film semiconductor materials, while keeping the cost low

If solar cell efficiency is to improve, light absorption by the semiconducting material must be increased.  To do this, GREEN is utilizing a unique approach in which they place a metastructure, or an engineered, complex metal structure, on either the top or bottom of plasmonic solar cells, a type thin-film solar cell.  When light particles hit the metastructure, they scatter across the cell, thus increasing the semiconducting material’s exposure to light.  The longer the light passes through the semiconductor, the more absorption occurs.  This metastructure application mimics the increased efficiency of a thicker, conventional semiconductor without the added size or cost.  While these applications are not yet ready for commercial implementation, they are producing favorable results with lots of developmental potential.  The implications of successful solar research include the alleviation of the global energy crisis and global warming, as well as economic development through job creation among various stages of solar cell production.

GREEN’s research is part of Arkansas’ Experimental Program to Stimulate Competitive Research (EPSCoR) grant, funded by the National Science Foundation.  This funding has allowed the team to purchase vital equipment otherwise inaccessible to them, and has propelled the capabilities of their research.  While expressing the gratitude he felt for such funding, Liming asserted, “Research is not limited by the researchers, but by their resources.”  As one of three poster contest winners at the Annual Advancing & Supporting Science, Engineering & Technology (ASSET) Conference this past July, Ji is presenting his findings at the National EPSCoR Conference October 24-27, 2011 and compete with other researchers for national research recognition.  After graduation, he plans to continue research in solar energy, either in Arkansas or abroad.  While Liming might not be able to stay in Arkansas in the immediate future, he is confident in this research and in the efforts of other Arkansas-based research projects.  He expects the solar energy industry will only grow and thrive in the state.   To find out more about this research, please contact Dr. Vasu Varadan at the University of Arkansas.


Please see our archive for a list of past featured researchers.