Professor Shawn-Yu Lin of Rensselaer’s physics department has published findings this week after a year-long project that can potentially help the solar industry overcome some of the major hurdles involving the percentage of solar absorption. Working with his team, Lin has produced a new antireflective coating that increases the amount of sunlight captured by solar panels, while also allowing the panels to take in sun from almost every angle.
“To get maximum efficiency when converting solar power into electricity, you want a solar panel that can absorb nearly every single photon of light, regardless of the sun’s position in the sky,” said Shawn-Yu Lin, Professor of Physics at Rensselaer and a member of the University’s Future Chips Constellation, who led the research project. “Our new antireflective coating makes this possible.”
Published in his paper “Realization of a Near Perfect Antireflection Coating for Silicon Solar Energy”, Lin demonstrated that a current untreated silicon solar cell absorbs about 67.4 percent of sunlight. This means that almost one-third of the sunlight shone on the cell is reflected away and unusable. But after the silicon surface is treated with Lin’s reflective coating, the panel absorbs 96.21 percent of the sunlight shone on it, allowing only 3.79 percent of the sunlight to be reflected. Remarkably, the large percentage of solar absorption was constant throughout the entire spectrum of sunlight including UV, visible light and infrared.
Along with absorbing over 28 percent more sunlight, the coating helped the panels absorb light from several different angles. A current solar panel absorbs the most light when the sun is shining directly on it; not from a side or skewed angle. Because of this, some solar arrangements are made to slowly move through the day so that the panels are always aligned with the sun showing directly on them. While this helps the panels to absorb more light, it is offset by the cost of up-keeping the mechanized system and any potential errors from misalignment, for example. Lin’s antireflective coating absorbs the light from all angles, equally and evenly, thereby potentially eliminating the need for mechanized systems and the additional cost they require.
“At the beginning of the project, we asked ‘would it be possible to create a single antireflective structure that can work from all angles?’ Then we attacked the problem from a fundamental perspective, tested and fine-tuned our theory, and created a working device,” Lin said.
Lin’s coating differs from the current antireflective coating, that can only transmit light from one particular wavelength, by stacking seven of the layers on top of one another in a way that each layer increases the antireflective properties of the layer below it and curves the sunlight being captured to angles that enhance the coating’s antireflective properties and therefore allows each layer to transit and capture light that may have previously been reflected off. Each of the seven layers has a height between 50 to 100 nanometers and is made from silicon dioxide and titanium dioxide nanorods, which were affixed to a silicon substrate via chemical vapor disposition. Lin claims that the his new coating can be joined to almost any photovoltaic materials for use in solar cells, including III-V multi-junction and cadmium telluride.
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