The research group of Hiroo Yugami et al. Of Tohoku University is the world's top solar photovoltaic power generation system (Solar-TPV) that converts sunlight containing light of a wide range of wavelengths into thermal radiation of the optimum wavelength for solar cells to generate electricity. Achieved a level of power generation efficiency of 5.1%.
The light emitted from the sun (heat radiation) has a wide wavelength distribution (spectrum).Single-junction solar cells (one type of semiconductor material) can only convert short-wavelength light into electricity (Note), so long-wavelength light is wasted.On the other hand, a multi-junction solar cell in which a plurality of solar cells are stacked can convert light of a wide range of wavelengths into electricity by expanding the wavelength range that can be absorbed.However, multi-junction solar cells have problems that they are difficult to manufacture and the production cost is high.
Solar-TPV is a photon-to-photon wavelength conversion system that converts sunlight into heat with a solar selective absorption material and then converts it into heat radiation from a wavelength-selective emitter (a device capable of wavelength-selective heat radiation). ..Therefore, it is necessary to efficiently convert the light energy into electric power (photoelectric conversion) after transporting the absorbed solar energy only to the wavelength selection emitter without loss.
This time, we proposed the conversion and transport efficiency of sunlight based on new concepts ("spectral control of thermal radiation" and "transportation of thermal radiation in one direction"), and newly performed optical design and geometric design.As a result, we succeeded in designing and manufacturing a solar selective absorption material and a wavelength selective emitter that can be expected to have a thermal radiation transport efficiency of 54% and a photoelectric conversion efficiency of 28%, and achieved the world's top level power generation efficiency of 5.1%.
The results of this research are expected to realize high-efficiency photovoltaic power generation based on a concept different from that of multi-junction solar cells.In addition, the concept proposed this time can be applied to various fields related to the effective use of unused energy.
(Note) Crystals have a region (band gap) in which electrons cannot exist, and in ordinary semiconductor materials, they exist in the long wavelength region.
