A relatively new type of semiconductor, superimposed on a mirror-like structure, can mimic the way leaves move energy from the sun over relatively long distances before using it to power chemical reactions. The approach could one day improve the efficiency of solar cells.
“Energy transport is one of the crucial steps in the harvesting and conversion of solar energy in solar cells,” said Bin Liu, postdoctoral researcher in electrical and computer engineering and first author of the study. in Optica magazine.
“We have created a structure capable of supporting hybrid light-matter mixing states, enabling efficient and exceptionally long-distance energy transport.”
One of the ways solar cells lose energy is through leakage currents generated in the absence of light. This happens in the part of the solar cell that takes negatively charged electrons and positively charged “holes”, generated by the absorption of light, and pulls them apart at a junction between different semiconductors to create an electric current.
In a conventional solar cell, the junction area is as large as the light-collecting area, so electrons and holes don’t have to travel far to reach it. But the disadvantage is the energy loss of these leakage currents.
Nature minimizes these losses in photosynthesis with large light-gathering “antenna complexes” in chloroplasts and much smaller “reaction centers” where electrons and holes are separated for use in sugar production. However, these electron-hole pairs, called excitons, are very difficult to transport over long distances in semiconductors.
Liu explained that photosynthetic complexes can handle it thanks to their highly ordered structures, but man-made materials are usually too imperfect.
The new device circumvents this problem by not completely converting the photons into excitons – instead they retain their luminous qualities. The photon-electron-hole mixture is called polariton. In polariton form, its light-like properties allow energy to quickly travel relatively large distances of 0.1 millimeters, which is even further than the distances traveled by excitons inside sheets.
The team created the polaritons by superimposing the thin, light-absorbing semiconductor onto a photonic structure that looks like a mirror, then illuminating it. This part of the apparatus acts like the antennae complex in chloroplasts, gathering light energy over a large area. Using the mirror-like structure, the semiconductor funneled the polaritons to a detector, which converted them into electric current.
“The advantage of this arrangement is that it has the potential to significantly improve the power generation efficiency of conventional solar cells where the light-gathering and charge-splitting regions coexist on the same area,” said Stephen Forrest, Professor Emeritus Peter A. Franken. of Engineering, who conducted the research.
Although the team knows that energy transport occurs in their system, they are not completely sure that the energy is constantly moving in the form of a polariton. It could be that the photon is somehow surfing a series of excitons on its way to the detector. They leave this fundamental detail for future work, along with the question of how to build efficient light-harvesting devices that exploit photosynthesis-like energy transfer.
The study was funded by the Army Research Office and Universal Display Corporation, and Universal Display Corporation licensed the technology and filed a patent application. Forrest and the University of Michigan have a financial interest in Universal Display Corp.
Forrest is also the Paul G. Goebel Professor of Engineering and Professor of Electrical Engineering and Computer Science, Materials Science and Engineering, and Physics.
Research report:Generation of photocurrents following the long-range propagation of organic exciton-polaritons
Related links
University of Michigan
All about solar power at SolarDaily.com
|
We need your help. The SpaceDaily news network continues to grow, but revenue has never been harder to sustain. With the rise of ad blockers and Facebook, our traditional sources of revenue through quality network advertising continue to decline. And unlike so many other news sites, we don’t have a paywall – with those boring usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful, consider becoming a regular supporter or, for now, making a one-time contribution. |
||
|
SpaceDaily Contributor $5 charged once credit card or paypal |
 |
SpaceDaily Monthly Supporter $5 billed monthly paypal only |
A major breakthrough for stable, high-efficiency perovskite solar cells
Linkoping, Sweden (SPX) 07 Sep 2022
Solar cells made from materials known as “perovskites” are catching up with the efficiency of traditional silicon-based solar cells. At the same time, they have the advantages of low cost and short energy payback time. However, these solar cells have stability issues – something that researchers at Linkoping University, together with international collaborators, have now managed to solve. The results, published in Science, are a major step forward in the search for next-generation solar cells. … Read more