Micro-pixel light emitting diodes with wavelength-tunable output

Abstract

A novel design and implementation of a single-chip wavelength tunable light emitting diode (LED) is introduced in this paper, with varying emission spectral characteristics ranging between 470 nm (blue) and 525 nm (green). The emission wavelength of green fluorescent microspheres (525 nm), acting as a colour conversion agent, is chosen to be efficiently excited by a GaN LED of 470 nm. It is selectively-coated onto designated micrometer-scaled pixels, which are interconnected via metal lines. As a result, the LED allows separate control of optical output either 470 nm, 525 nm or even a mixture of both wavelengths. Since the pixels are of micronscale which are non-resolvable by the unaided human eye, the output appears optically mixed. This type of device, combining the application of micro-light-emitting diode and fluorescent microsphere technologies, offers a colour tunable output suitable for a wide range of applications including such as outdoor panel displays. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.