UCLA researchers have developed a two-layer, transparent solar film for windows, sunroofs, tablet and smartphone displays to harvest energy from the sun. This group nearly doubled the efficiency of their record-breaking solar cell from last year in their latest accomplishment.
The research was published online July 26 by Energy & Environmental Science, a Royal Society of Chemistry journal; it will appear later in a published print edition of the journal.
The major improvement in efficiency was mainly due to the incorporation of an additional cell that allows more light to be absorbed than single-layer solar devices, since it can receive light from a larger array of the solar spectrum, in addition to the novel materials between the two cells that reduces energy loss.
The tandem-structure transparent flexible organic photovoltaic (TOPV) device developed at UCLA in 2012 converts only about 4 percent of the energy it receives from the sun into electric power; however, the new tandem device, which uses a combination of transparent and semi-transparent cells, achieves a conversion rate of 7.3 percent. On the dark side, this is still significantly less than the nearly 20 percent level of conventional crystalline silicon solar cells, constituting over 80 percent of the market. Transparent solar cells offer clear game-changing benefits over conventional solar products, but it will take at least another decade before they become mainstream.
The tandem polymer solar cells are composed of a photoactive plastic. A single-cell device absorbs only about 40 percent of the infrared light that strikes it, but the tandem device, including a cell composed of a new infrared-sensitive polymer, absorbs up to 80 percent of that light as well as a small amount of visible light. Applications for the new cells include dual-purpose power-generating layers on windows and mobile device displays without lessening the normal viewing quality of the surface. The cells can be produced in various tints such as light-gray, green or brown and ultimately mix with the color and design features of buildings and surfaces.
In more recent solar industry news, JA Solar, the world’s largest solar cell producer based in Shanghai, China, reported yesterday a record solar cell efficiency of 18.3 percent for a standard (156×156 mm2) multicrystalline solar cell, which is based on more mature technology than organic solar cells. Its record-breaking cell performance has been verified by the Yangzhou Opto-Electrical Products Testing Institute in China. The company noted that the improvements were the result of its R&D efforts to increase crystalline silicon quality, while reducing the dislocation defect density in multicrystalline casting and related wafer processes. The superior conversion efficiency achieved in this effort increases the power generated per square foot of a solar panel and lowers installation cost per watt, which are both key factors for the implementation of more solar projects globally.
Amid the recent accomplishments of numerous solar cell technology leaders this past year, the solar industry is only slowly recovering from its panel oversupply and downturn over the last several years, which continues to generate more consolidation and restructuring of many players throughout the supply chain.
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