LED Research Group

A Light Emitting Diode (LED) is a solid state light source that emits light by the electroluminescence effect. LEDs utilize the radiative recombination process of electrons and holes to generate light through photon emission. Electrons and holes are pumped into the space charge region in multiple quantum wells (QWs) under forward bias and they recombine to emit light.

The increasing demand for light emitting diodes (LEDs) has been driven by a number of application categories, including display backlighting, communications, medical services, signage, and general illumination. One barrier to the acceptance of LEDs in these applications is the relatively sparse information available on their reliability. There are many areas in need of improvement and study regarding LEDs, including the internal quantum efficiency of the active region, light-extraction technology, current-flow design, the minimization of resistive losses, electrostatic discharge stability, increased luminous flux per LED package, and purchase cost.

The construction of LEDs is somewhat similar to microelectronics, but there are functional requirements, materials, and interfaces in LEDs that make their failure modes and mechanisms unique. This means that comprehensive industry and academic research are required on LED failure mechanisms and reliability to help LED developers and end-product manufacturers focus resources in an effective manner. The reliability information provided by the LED manufacturers is not at a mature enough stage to be useful to most consumers and end-product manufacturers.

CALCE LED research group is providing the groundwork for an understanding of the reliability issues of LEDs across failure causes and their associated failure mechanisms, issues in thermal management, and critical areas of investigation and development in LED technology and reliability.

The goals of the CALCE LED research group are to improve the reliability and the qualification of LEDs for the LED manufacturers and LED lighting companies to better understand the LED failure mechanisms and useful lifecycle dynamics.

  • Knowledge-based qualification methods to develop data-driven, physics of failure (PoF) based, and fusion prognostic techniques for LEDs
  • Development of reliability improvement methods for LEDs utilizing prognostics and health management techniques:
    • To facilitate faster product development
    • To identify reliability risks under application conditions and mitigate them
    • To improve integration of PHM in LED lighting systems.