Evaluation of the internal quantum efficiency in light-emitting diodes

Abstract

A new evaluation method for the internal quantum efficiency (IQE) in light-emitting diode (LED) packages is presented. In order to derive this IQE model, we introduce the thermal resistance concept composed of the effective internal optical power in LED packages. This IQE evaluation method needs precise measurements of the thermal properties, as well as the electrical and the optical properties in the LED packages. Also, numerical simulations of the internal thermal gradients in the LED packages, based on computational fluidic dynamics, should be included to evaluate the IQEs in LED packages. A high-power ceramic LED package was developed for the experiment on the IQEs, and we measured the IQEs of LED packages at various operation conditions and compared the results with those obtained by the conventional electroluminescence (EL) method. Our method is a simple EL-based method with thermal insight onto LED packages. Contrary to conventional EL methods, our method makes no assumption of the carrier injection efficiency and does not require a very low current injection level in the LED packages.