A typical solar cell, at max, converts <33% of light into electricity, so researchers have been working to find ways to surpass this limit. In the past, scientists have put an extra photon upconversion filter before or after the cell to catch the low energy, unused light and convert it into usable, high-energy light. But, FSU Assistant Prof Hanson wanted to integrate this process directly into the cell.
The researchers did this by using self-assembly. Through a soaking procedure, they assembled 2 molecules, an acceptor and sensitizer, on a surface which work in concert to perform photon upconverion, ie via triplet–triplet annihilation (TTA-UC) combining 2 low energy, green photons to generate a higher energy, blue photon, which can then be used to generate electricity. Using this process in an optimized solar cell can increase efficienty to 45%. The team is also confident they can generate even better numbers in the future.
“It’s definitely a stepping stone toward making more efficient solar cells,” Hanson said. “Our current work demonstrates a feasible method.” A recent Department of Energy study estimates that solar energy, which is 0.05 of the current power supply, will grow to 14% by 2030 and 27% by 2050.
This strategy is simple, modular and offers unprecedented geometric and spatial control of the donor–acceptor interactions at an interface. These results are a key stepping stone toward the realization of an efficient TTA-UC solar cell that can circumvent the Shockley–Queisser limit. http://pubs.acs.org/doi/10.1021/acs.jpclett.5b02120
Photon Upconversion and Photocurrent Generation via Self-Assembly at Organic–Inorganic Interfaces
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