Final Report: Highly Bright, Heavy Metal-Free, and Stable Doped Semiconductor Nanophosphors for Economical Solid State Lighting AlternativesEPA Contract Number: EPD07037
Title: Highly Bright, Heavy Metal-Free, and Stable Doped Semiconductor Nanophosphors for Economical Solid State Lighting Alternatives
Investigators: Battaglia, David
Small Business: Nanomaterials & Nanofabrication Laboratories
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2007 through August 31, 2007
Project Amount: $69,988
RFA: Small Business Innovation Research (SBIR) - Phase I (2007) RFA Text | Recipients Lists
Research Category: SBIR - Water and Wastewater , SBIR - Pollution Prevention , Small Business Innovation Research (SBIR)
By using D-dot™ nanophosphors, white LEDs can be made significantly more efficient than bulk phosphors, which suffer from backscattering losses. The photoluminescence quantum yield (PL QY), a measure of light conversion efficiency, of yellow and orange D-dots™ was increased to nearly 70 percent during the project, positioning D-dots™ well within range of the intrinsic PL QY of bulk phosphors. However, because there is approximately a 50 percent loss in overall device efficiency from optical scattering, the effective PL QY of bulk phosphors falls to 20– 30 percent below that of D-dots™. In addition, D-dots™ were successfully incorporated into LED encapsulants with close to 100 percent optical clarity without loss of PL QY, displaying nearly 100 percent chemical stability. Currently, the main technical issues preventing immediate use of D-dots™ in SSL were less than desirable photostability under high illumination intensities, which is expected from high brightness LEDs, and a lack of other emission colors, such as red and green. Judging by the overall progress made in this Phase I program, both of these issues could be resolved in the Phase II program.
A commercial feasibility study was conducted to determine if selling D-dot™ nanophosphors for use in SSL devices could become a profitable enterprise. It was found that D-dots™ could, in fact, enable SSL devices to reach the levels of high efficiency and low cost necessary so that SSL devices could overtake both incandescent and fluorescent lamps within 3– 5 years. Even with a moderate projected market share, revenue from D-dot™ sales could reach over $100 million in 5 years.
Prototype nanophosphor- based LEDs were fabricated and tested using orange and yellow D-dots™ . Overall device wall plug efficiencies ranged from 25 lm/W to 43 lm/W, and total lumen output was 33 lm at 25 lm/W. The limiting factor was the lower efficiency of the LED chips rather than the D-dot™ nanophosphors. Conservative projections of improvements to the LEDs and to the D-dots™ show single chip SSL devices with a total lumen output of 1130 lm at wall plug efficiencies of 113 lm/W. The cost of such a device would be about $0.004 per lumen, allowing D-dot™-enabled white LEDs to compete with fluorescent lamps.
This SBIR Phase I research focused on demonstrating the technical and commercial feasibility of a business enterprise to sell doped semiconductor nanophosphors for use in SSL devices, enabling them to become efficient and inexpensive, and to out-compete mercury-containing fluorescent lamps and inefficient incandescent bulbs. The focus of the Phase II program will be on product development and synthesis scale-up of a full spectral range of doped semiconductor nanocrystal phosphors with high PL QY , as well as more focus on commercial aspects. This technology will have far-reaching environmental impact. The overriding vision is to replace billions of mercury-containing fluorescent lights with non toxic nanophosphor SSL units, which will effectively eliminate a major source of mercury release into the environment.