An electron microscopy image of tin-doped indium oxide nanoparticles (source: Kyoto University)
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A glass substrate to which tin-doped indium oxide nanoparticles have been applied (source: Kyoto University)
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A Japanese research group announced Feb 13, 2019, that it has developed a colorless, transparent material capable of converting infrared light into electricity, signals, etc.

The new material is expected to be used for the development of cutting-edge devices such as invisible solar cells, communication devices and optical sensors. The group consists of researchers from Kyoto University, Toyota Technological Institute, Tokushima University, National Institute of Advanced Industrial Science and Technology (AIST), etc.

There have already been colorless, transparent materials that can convert ultraviolet light into energy, signals, etc. However, ultraviolet light is not suited for communications or energy conversion. So, there had been a need to develop a material that can convert infrared light, which has a long wavelength and is invisible, into electricity, signals, etc.

This time, the research group used an inorganic nanoparticle that shows localized surface plasmon resonance (LSPR) with light in the infrared region. It aimed to realize both electron transfer by infrared light and transparency by using (1) tin-doped indium oxide nanoparticles, which show LSPR with light in the infrared region and can control the absorption wavelength by controlling the amount of doping, as a light-harvesting material and (2) tin oxide as an electron acceptor.

A tin-doped indium oxide nanoparticle film formed on a glass substrate became a colorless, transparent material that has a transmittance of 95% with visible light and a high absorption rate with infrared light. After making oxide carriers (titanium oxide, tin oxide and silica), which are electron acceptors, carry tin-doped indium oxide nanoparticles, a connection with oxide carriers was formed by sintering.

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