AsianScientist (May 16, 2017) – In a study published in Nature Communications, researchers describe a solar cell design that can raise the energy conversion efficiency to over 50 percent by absorbing the spectral components of longer wavelengths that are usually lost during transmission through the cell.
Solar cells convert the sun’s energy into electricity by converting photons into electrons. In theory, 30 percent energy-conversion efficiency is the upper limit for traditional single-junction solar cells, as most of the solar energy that strikes the cell passes through without being absorbed, or becomes heat energy instead.
Experiments have been taking place around the world to create various solar cell designs that can lift these limitations on conversion efficiency and reduce the loss of energy. The current world record is at 46 percent for a four-junction solar cell. If the energy-conversion efficiency of solar cells surpasses 50 percent, it would have a big impact on the cost of producing electricity.
In order to reduce these large energy losses and raise efficiency, a team led by Professor Kita Takashi and Project Assistant Professor Asahi Shigeo at Kobe University, developed a new solar cell structure for generating photocurrents. They used two small photons from the energy transmitted through a single-junction solar cell containing a hetero-interface formed from semiconductors with different bandgaps.
In addition to demonstrating theoretical results of up to 63 percent conversion efficiency, the researchers experimentally achieved up-conversion based on two photons, a mechanism unique to this solar cell. The reduction in energy loss demonstrated by this experiment is over 100 times more effective compared to previous methods that used intermediate bands.
The team will continue to design solar cells, and assess their performance based on conversion efficiency, working towards a highly efficient solar cell for low-cost energy production.
The article can be found at: Asahi et al. (2017) Two-step Photon Up-conversion Solar Cells.
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Source: Kobe University; Photo: Shutterstock.
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