High Extraction Luminescent Material Structures for Solid State Light Emitting Diodes

75849-Solid state lighting is rapidly gaining momentum as a highly energy-efficient replacement technology for incandescent, and eventually fluorescent, lighting. However, current solid state devices suffer from poor-light-extraction efficiencies. This project will develop new, low-cost luminescent structures to greatly increase the light-extraction efficiency from standard light-emitting-diode (LED) structures by as much as a factor of three. The new concept maximizes output coupling through detailed control of the optical properties (refractive index, scattering, absorption, luminescence efficiency, etc.) of the materials surrounding the LED die. The approach will use an electrophoretic deposition technique suitable for high-volume production of LEDs and LED arrays. Phase I will concurrently investigate various sulfoselenide phosphor material systems to optimize their high refractive index properties to the LED die. This activity will be supported by the development of appropriate optical models to simulate their light extraction and down-conversion properties to white light. The goal of Phase II is the development of a white LED having a luminous efficiency greater than 100 lm/W. Commercial Applications and Other Benefits as described by the awardee: The high efficiency luminescent structures should have immediate application to markets where LEDs already are being used, such as portable electronics, automobiles, and traffic signaling. The increased efficiency also should open new markets where traditional light sources currently dominate, leading to significantly reduced energy requirements, lower levels of pollution, reduced toxic waste (e.g., Hg from fluorescent lamps), and a reduced dependence on foreign oil suppliers.