Materials for the next-generation display and illumination
LCDs with a back light of white LED are widely used for TV and computers as a low-environment-impact displays. The white LED is realized by combination of GaN-based blue LED and yellow fluorescent; however this system is not perfect because the present white LED does not contains deep red color. The next-generation high-color-gamut display needs new material.
To reproduce the color with higher fidelity, new fluorescents which convert blue light of LED into red and green light are required. The nano-scale compound semiconductor, quantum dots, which we also introduced in the page of next-generation solar cell, have unique property that the emission color changes depending on their size. So we can obtain the various emission colors by single material and improve the color purity by controlling their size. The display using quantum dots are already getting on the market like Kindle Fire and Sony Triluminos display. The material used for quantum dot display is generally CdSe, which contains cadmium and subjected to the legal limitation in Japan and EU. The new material for quantum dots containing no toxic elements are required.
In our lab, we selected some cadmium-free semiconductors which are expected as visible light fluorescent by simulations. So far, we succeeded in fabrication of CuInSe2-based quantum dots ahead of other labs in the world. Quantum dots are applicable for a light source of UV or IR as well; we also succeeded in fabrication of ZnO-based quantum dots which emits UV light. In the present, we design and develop higher quality, eco-friendly quantum dots.