Liming Ji

Liming Ji came to the United State to pursue his Ph.D. 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 lowe the cost of solar cells. This is a central goal of the GREEN Research Center for Nanoplasmonic Solar Cells team of which Ji is a part.

The most expensive aspect of a solar cell production is the preparation of the semiconductor material, which absorbs light energy and converts it into electrical energy. This semiconfucting 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, researchers no 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 engineerd, complex metal structure, on either the top or bottom of plasmonic solar cells, a type of 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 incrased efficiency of a thicker, conventional semiconductor without the added size or cost. While these applications are not yet ready for commercial impementation, 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 though 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 gratitutde 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 competing 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 expexts the solar energy industry will only grow and thrive in the state. To find out more about this research, please contact Dr. Vasundara Varadan at the University of Arkansas.


Update: Liming was awarded the 2012 Institute of Electrical and Electronics Engineers (IEEE) AP Graduate Student Scholarship for his proposal on Solar Nano Antennas. He is a candidate for August 2012 graduation from the University of Arkansas with a Ph.D. in Electrical Engineering.