Licensable Technologies : Materials : Polymers

Colloidal Quantum Dot Light Emitting Diode (CQDLED)

Abstract
Numerous technologies including solid-state lighting, displays, and traffic signals can benefit from efficient, color-selectable light sources that are driven electrically. Semiconductor nanocrystals (nanocrystal quantum dots) are attractive chromophores that combine size-controlled emission colors and high emission efficiencies (potentially 100 %) with excellent photostability and chemical flexibility. Applications of nanocrystals in light-emitting technologies, however, have been significantly hindered by difficulties in achieving direct electrical injection of carriers. LANL scientists have developed a nanocrystal-based light-emitting diode in which semiconductor nanocrystals are incorporated into a p-n junction formed from GaN injection layers. The critical step in the fabrication of these nanocrystal/GaN hybrid structures is the use of a novel deposition technique (energetic neutral atom beam lithography/epitaxy) that allows for the encapsulation of nanocrystals within a GaN matrix without adversely affecting either the nanocrystal integrity or emission efficiency. Biasing the junction above the threshold voltage (currently 3V) results in charge injection into nanocrystals from both p-type and n-type GaN layers. Electron-hole recombination events within nanocrystal quantum dots release photons. The energy of output photons and therefore the color of light can be easily tuned by changing nanocrystal size. By using multilayers of nanocrystals of different sizes it is possible to produce multicolor emission or white light. LANL researchers have constructed and tested light sources using this technology.

Application(s)

• General Illumination Displays
• LED Signs Automotive
• Lighting Traffic signs
• Tunable Laser Diodes 

Advantages

• Emission wavelengths (color) can be controlled by nanocrystal size or by using mixtures of sizes
• Low-voltage operation from infra-red through visible to ultraviolet Improved efficiencies compared to traditional devices utilizing phosphor materials
• Improved stability compared to organic LEDs High output powers (estimated at 10 W per square cm in nanocrystal monolayers)  

IP Status: Available both Exclusively and Non Exclusively

Reference Number: 292

S Number: DOE reference no.(s): 102,303

Patents & Applications:
Application(s) Pending

Posted: 02-18-2005

Contact
Laura Barber
Technology Transfer Division
Los Alamos National Laboratory
P.O. Box 1663, MailStop C334
(505) 667-9266
ljbb@lanl.gov