Drew Fleming - Featured Researcher

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This December, Drew Fleming will graduate with his Master’s Degree in Mechanical Engineering from the University of Arkansas.  As part of the Vertically Integrated Center for Transformative Energy Research (VICTER) Team, Fleming works to adapt the nano materials and surface engineering of thin-film solar cells to produce a less expensive, better functioning product capable of aiding the transition from fossil fuel based energy to renewable solar energy.  As with any manufacturing process, solar cell production occurs over several development stages.  This group of researchers is unique in that they focus on improving the first and last of those stages:  the materials and the packaging.

In solar cell packaging, the last, outermost component is a piece of glass.  Like any surface exposed to the elements, the glass tends to get dirty which reduces the influx of light and potential energy generated by the cell.  This results in only 92% optical transmittance to the semiconducting material beneath the surface of the cell.  Semiconducting materials are the central and most vital part of any solar cell; their job is to absorb light and convert it into electrical energy.  And, in addition to the optical transmittance limitation, there is yet another challenge facing solar cell efficiency:  the reflectivity of semiconducting materials.  According to Fleming, the most effective and cost efficient semiconducting materials tend to be very reflective, at times up to 30%.  These two deficiencies leave the overall energy production of the cell reduced to about 60%.  To combat this during the materials stage, the VICTER team is working to develop anti-reflective coatings for the tiny, thin-film semiconducting materials.  “The materials we are using are much smaller than most people would realize.  [We have] particles & films with dimensions of 100 nanometers (nm).  That is a hundred to a thousand times smaller than the thickness of a human hair,” said Fleming.  Their materials work is still quite young, but it is already showing promise.

The most market-ready aspect of this VICTER team’s research pertains to packaging applications, called surface wetting modifications.   Surface wetting refers to modifying the way in which water interacts, or forms droplets, on a surface.  The team has been hard at work creating a surface that combines superhydrophilic (water loving) and superhydrophobic (water hating) properties.  On a superhyrdrophilic surface, the water preferentially spreads into a thin uniform sheet, but on superhydrophobic areas the water balls up into spherical droplets and will not adhere to the surface.  Additionally, these cell surfaces are engineered with a slight roll-off angle, so as water droplets form on the cell, they will roll down the incline picking up dirt and debris as they go right over the edge, essentially creating a self-cleaning façade.  Through these efforts, this VICTER research group is well on their way to producing a less expensive and better functioning solar cell.

Because of his poster entry this past July at the Annual Advancing & Supporting Science, Engineering & Technology (ASSET) Conference, Mr. Fleming is one of three graduate students representing Arkansas at the National EPSCoR Conference in Idaho October 24th through the 27th.  EPSCoR, or Experimental Program to Stimulate Competitive Research, is a nation-wide program funded by the National Science Foundation.  Through this grant and financial support, the VICTER team has secured unlimited access to the nano-fabrication laboratory at University of Arkansas, without which, they would have been unable to engineer their surface wetting modifications.  The increased emphasis on research actually brought Drew back to Arkansas to continue his education.  While he completed his undergraduate degree in Mechanical Engineering at U of A, he left for Illinois to pursue his Masters; that is until he learned about the research efforts developing after he left.  He returned one semester later and has since helped generate exciting advances in efficient, cost effective solar cells.  When reflecting on his experience, Fleming said, “At the end of the day, everyone on the VICTER team is genuinely concerned about improving solar cell technology…they want it to be successful, and there is a lot of potential.” To learn more about this research, please contact Dr. Min Zou at the University of Arkansas.