Multi-Junction Solar Cells and Solar-TPV System Features Northeastern University of Japan announced on October 25, 2016 that the solar-thermal power generation (Solar-TPV: Solar-thermophotovoltaic) system has achieved a power generation efficiency of 5.1%, reaching the highest level in the world. The principle of this kind of power generation system is to convert sunlight containing light of a wide range of wavelengths into heat radiation of a wavelength best suited to a solar cell and generate electricity. It is expected to realize high-efficiency photovoltaic power generation different from the concept of multi-junction solar cells. The light (thermal radiation) emitted by the sun has a wide wavelength distribution (spectrum). A single-junction solar cell can only convert light with a wavelength smaller than the bandgap of the semiconductor material used into electrical energy, and other wavelengths of light cannot be converted into electrical energy and become lossy. A multi-junction solar cell formed by overlapping a plurality of solar cells can convert the solar spectrum into electric energy without waste by expanding the absorbable wavelength region. However, there is a problem of high production cost compared with single junction solar cells. Solar-TPV heats the solar light selective material and the wavelength selective emitter by collecting sunlight, and then the photoelectric conversion unit uses the heat radiation emitted by the wavelength selective emitter and matched with the sensitivity wavelength region to generate electricity. The characteristic of sunlight is that it can be converted into heat first, and then converted to light of other wavelengths (thermal radiation) when the sum of the contained photon energy is constant. In this way, high-efficiency power generation can be achieved even with the use of inexpensive single-junction solar cells. In this study, Tohoku University proposed a new scheme based on the concepts of “heat radiation spectrum control†and “thermal radiation unidirectional transportation†to improve heat radiation conversion and transportation efficiency, and based on this concept Solar- The overall design of the TPV system. The Solar-TPV system converts sunlight into heat radiation and is a wavelength conversion system that converts photons into each other, unlike the traditional concentrating solar thermal power generation that converts sunlight into heat. Therefore, the focus of efficiency improvement is to deliver the absorbed solar energy to the wavelength selective emitter without loss so that the spectrum of thermal radiation emitted by the wavelength selective emitter matches the sensitivity wavelength region of the photoelectric conversion unit. That is, it is required to have a high "heat radiation conversion and transportation efficiency" and "photoelectric conversion efficiency." Both of these efficiencies can be enhanced by the optical design and geometric design of the solar selective absorber material and wavelength selective emitter. The requirement for selecting the absorbing material for sunlight is that it has a high absorptivity in a short wavelength region where the solar light has a large spectral intensity and a low emissivity (absorption) in a long wavelength region. The wavelength selective transmitter is required to have high emissivity in the sensitivity wavelength region of the photoelectric conversion unit and low emissivity in other wavelength regions. This time, the researchers designed an area ratio that can achieve higher heat radiation conversion efficiency and transport efficiency, suppress the reflection and radiation loss of solar light selective absorbing materials, and successfully designed and produced a heat radiation transport efficiency that is expected to reach 54%. , Opto-electronic conversion efficiency is expected to reach 28% of solar selective absorbers and wavelength selective emitters. In a power generation test using a trial-made solar selective absorbing material, a wavelength selective emitter, and a germanium photoelectric conversion unit, the power generation efficiency reached 5.1%. Relevant research results were published on Applied Physics Express on October 25, 2016, and were selected as Spotlights papers. (Special Contributor: Kudosuke) Specification PTFE Gasket Glass Fiber PTFE Gasket,PTFE Seal Gasket ,White PTFE Gasket,Black PTFE Nylon Gasket ZHENJIANG CHUNHUAN SEALING MATERIALS CO.,LTD(GROUP) , https://www.chsealing.com
Summary of Solar-TPV system 
(a) Solar Selective Absorbent Materials and (b) Optical Properties of Wavelength Selective Emitters
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