Efficacy Limits for Solid-State White Light Sources
Several recently published road maps for solid-state light have called for systems with efficacies of 200 to 240 lm/W. Luminous efficiency, or efficacy, is a common performance metric for light sources. It is the ratio of the perceived brightness to the input power and, because the brightness of a light source is measured in lumens and electrical power is measured in watts, the units of efficacy are lumens per watt. Several assumptions were made to arrive at the 200 to 240 target, with only...
Photonics Spectra, March 2007