Thursday, July 17, 2014

New Finding Could Increase Solar Efficiency By 30%

Solar industry is a non-stopping battle ground of price and performance. Now, scientists from University of California, Riverside, U.S.A., has found a way to use one photon to generate 2 electrons, which theoretical could boost solar efficiency.

What is photon? Photon is an elementary particle of light. When we see different color of light it is simply photon with different wavelength and energy. When light, or photon, strikes the solar cell, they will penetrate and be absorbed by the solar material. Electron will be generated and electricity will flow when the cell is connected to a load.

Conventionally, one photon will only generate one electron. But newly discovery could double the generation. The technique is called singlet fission, in which an initially excited singlet state spontaneously splits into a pair of triplet excitons, boosting the overall solar efficiency by as much as 30%.

Here’s the Bardeen lab’s diagram of how singlet fission works to spontaneously split into two triplets, effectively dodging the efficiency barrier of the Shockley-Queisser limit.

“The exact mechanism is unknown, but it does happen quickly—at the sub-nanosecond timescale—and with high efficiency,” said Prof. Bardeen, who led the research.

Prof. Bardeen cites recent work at MIT that has already demonstrated an organic photovoltaic cell with more than 100% external quantum efficiency based on this effect. Prof. Bardeen believes similar improvement can be observed in inorganic semiconductors.

The next move of the team is to find new materials that exhibit singlet fission, figuring out how to turn the triplet excitons into electricity.

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