Improved Light Extraction for Solid State Lighting

SUMMARY

Lehigh University has developed a new, low-cost method to achieve enhanced light extraction efficiency for III-Nitride LEDs. Conventional LEDs with planar emission surface suffers from limited external quantum efficiency. The large refractive index difference in the semiconductor / air interface results in total internal reflection. This leads to narrow escape cone and low light extraction efficiency causing limited external quantum efficiency.

Specifically, this invention increases the light extraction of optoelectronic emitters by utilizing a SiO₂/ polystyrene (PS) microlens array deposited on the surface on the light emission area. The implementation of these microspheres leads to a low-cost and straight forward approach without using costly electron-beam lithography process. The diameter of the microspheres can be controlled accurately for repeatability in the microlens structure and optical properties. Additionally, because the SiO₂microspheres are deposited as the final step, this avoids any degradation on the electrical characteristics of the optoelectronic emitters.

Applications for this invention include SSL, biochemical sensing, and water purification.

Lehigh Tech ID# 122406-01

THE MARKET

The SSL market is predicted to reach $33 billion by 2013, growing annually at over 10%.[1] This market is an umbrella market for LEDs, OLEDs, and PLEDs. LED technologies make up a majority of this market ($5.08 billion), with a growth rate of over 24%.[2] Additionally, 22% of the United States electricity is consumed by lighting, which costs consumers over $50 billion each year. SSL technologies have the potential to reduce this consumption by up to six times less. This potential has led to increased market need, funding resources and science centers dedicated to SSL developments, such as the $46 million Energy Frontier Research Center (EFRC) for solid-state lighting science funded by the Department of Energy.[3]

[1] “Solid-State Lighting Market Will Reach $33 Billion Worldwide by 2013.” AZooptics.com web site. http://www.azooptics.com/Details.asp?NewsID=3867 (accessed September 28, 2010).

[2] About Us.” GE Lumination web site. http://www.lumination.com/overview.php (accessed September 28, 2010).

[3] Solid-state lighting's contributions to national energy efficiency discussed at AAAS meeting.” February 21, 2010. PHYSORG web site. http://www.physorg.com/news185943042.html (accessed

September 28, 2010).

THE OPPORTUNITY

Lehigh University is interested in identifying an industry partner to license this technology.