Abstract: A color tunable light emission diode in which the color tone of the emission color changes by controlling the injection current, which has an active layer sandwiched between a p-type layer and an n-type layer on a substrate, and the active color layer is formed by doping Eu and Mg to an AlGaInN-based material which is GaN, InN, AlN or a mixed crystal of any two or more of them; and a micro LED display, wherein its display unit is formed by integrating image pixels having the above color tunable light emission diode are provided; and a light emitting semiconductor device technology capable of providing an ultra-small and high definition micro LED display can be provided.

Abstract: A photovoltaic device is provided comprising an energy conversion material. The energy conversion material comprises nanosized semiconductor quantum structures comprising a first quantum dot and a second quantum dot. The first quantum dot has a first size, and the second quantum dot has a second size. The separation of the first and second quantum dots is of the same order of magnitude as the first or second size or smaller, such that, by irradiating the first quantum dot with a photon for producing one or more excitons in the first quantum dot, one or more further excitons are also produced in the second quantum dot.