News: LEDs
2 September 2024
Lumileds addresses micro-LED efficiency through EQE and directionality
LED product and lighting maker Lumileds LLC of San Jose, CA, USA says that, in the past few years, it has realized significant external quantum efficiency (EQE) performance for micro-LEDs. However, for micro-LEDs, and display applications in particular, EQE on its own is not a sufficient measure of performance.
To properly assess the efficiency of a micro-LED, one must also be able to measure the directionality of the light, says Lumileds. The directionality of light is critical for micro-LED displays, and displays are hence often characterized by radiant or luminous intensity, as seen from an angle.
“Most LEDs emit the majority of light from their top surface. This is especially true for thin-film LEDs,” notes Brendan Moran, Lumileds’ senior director of micro-LED development. “When we shrink the size of thin-film LEDs to become micro-LEDs, the side-emitting surfaces become a significantly greater portion of the overall light-emitting surfaces,” he adds.
“The thickness of what we described as a thin film for a larger-size LED now becomes substantial relative to the length and width of the micro-LED. This is a key reason why micro-LEDs emit a large portion of light from their sides, resulting in a wide viewing angle distribution and a reduction of intensity emitted from the top surface. For display applications, even high-EQE micro-LEDs can have relatively low on-axis intensity.”
The Lumileds R&D team has now developed micro-LEDs with a highly desirable light distribution that approximates Lambertian distribution. The team’s innovation is said to result in brighter displays that consume less energy.
Moran is presenting on micro-LED advances and efficiencies at the PlayNitride MicroLED Technology Forum in Taipei, Taiwan (3 September).
