Generally, when a substance is heated, the thermal motion of electrons inside the substance becomes intense, and light of various wavelengths is emitted (heat radiation).Sunlight, which is a type of thermal radiation, contains not only visible light but also various components such as ultraviolet rays and infrared rays.On the other hand, the light that can be efficiently converted into electricity by a general solar cell is only a small part of the wide wavelength component of sunlight, the light near the boundary between visible light and near infrared light, and other components cannot be effectively used.Therefore, the power generation efficiency of general solar cells remained around 20%.

　In this joint research, by forming a photonic nanostructure using silicon, which is a semiconductor material, we will develop a thermal radiant light source that emits only light of a wavelength that a solar cell can efficiently generate when it is heated to a high temperature. succeeded in.When the light source is heated by condensing sunlight, all of the collected light energy is converted into light that can be effectively used by the solar cell and emitted.Therefore, if the light is received by a solar cell to generate electricity, a very high efficiency of 40% or more is expected.Further, since the heat source is not limited to solar heat, high-efficiency power generation can be similarly performed by using combustion heat or the like.

　This achievement was published in "Science Advances," a sister paper of the American scientific journal "Science," on December 2016, 12.In February of the same year, he received the "Green Photonics Awards" for innovative research that contributes to the realization of a sustainable society at SPIE Photonics WEST, one of the world's largest international conferences related to optics.