U.S. Department of Energy - Energy Efficiency and Renewable Energy

Building Technologies Office – R&D Projects

Cree Sets New Benchmarks for LED Efficacy and Brightness

Photo of an LED: a bright semi-globe atop a square substrate.

Cree XLamp® XP-E LED provides lighting-class performance in a small-footprint, low-profile LED package.

Cree has successfully created a cool white LED prototype that delivers 107 lm/W at 350mA. This achievement builds on the Cree EZBright® LED chip platform, developed in part with prior funding support from DOE. Cree made the prototype LED under their DOE project focused on developing LED chips incorporating photonic crystal elements for improved light extraction and novel package technology for higher down-conversion efficiency compared to conventional LEDs. Based on a 1 millimeter-square chip, the new prototype LED produces white light with a CCT of 5500K and a CRI of 73. Integration of four of these prototype LEDs can produce luminous flux of more than 450 lumens.

 

Prototype LED Component "Instant-on" Integrating Sphere Test

Key Performance Metrics at 350 mA
Device Lumens Vf(V) LPW CCT(K) CRI
1 119.7 3.21 106.5 5600 72.7
2 120.5 3.20 107.6 5450 72.6
3 119.8 3.22 106.4 5550 74.8

Cree's investigation of the performance of three lab-sample cool white LEDs used an integrating sphere calibrated against LEDs tested at the National Institute of Standards and Technology (NIST)

Initiated in October 2007, the goal of this project is to create a novel warm white lamp module for insertion into high efficiency SSL luminaires. The project will address LED chip and package efficiency improvements to establish a technology platform that is capable of scaling into low cost, high efficiency commercial luminaires. The ultimate goal will be to replace halogen, fluorescent and metal halide lamps.

Cree sees the greatest improvement potential in blue chip external quantum efficiency, with part of the challenge being to move the efficacy curve up at a reasonable cost, toward an aggressive goal of 120 lm/W in the near future.

A horizontal bar chart entitled "Neutral White Component - Efficiency Breakdown:Q4 '07 Status—95 lm at 84 lm/W", with Percent on the horizontal axis. The top bar, Phosphor Stokes shift, is near 80. The next bar down, Conversion Efficiency Excluding Stokes, is at 70. The next bar down, 1QE, is a little more than 80. The next bar down, Chip Light Extraction Efficiency, extends to 70. The bottom bar, Chip Resistive Efficiency, extends a little past 80. The top two bars, representing down-conversion efficiency, is ~ 56%.  The bottom three bars, representing Chip wall-plug efficiency, is ~ 48% (460 nm, 3.25 V, 350 mA).

Cree's DOE project is targeting a 40% overall gain in efficacy at 350mA by focusing on chip light extraction efficiency and down-conversion efficiency excluding Stokes loss, the current main losses.