Modeling high power light-emitting diode spectra and their variation with junction temperature

Abstract

Spectral radiant flux is the primary optical characteristic of a light source, determining the luminous flux and color. Much research is dedicated to the modeling of light-emitting diode (LED) spectra and their temperature dependence, allowing for the simulation of optical properties in various applications. Most of the spectral radiant flux models that have been published so far are purely mathematical. For this paper, spectral radiant fluxes of commercial single color LED packages have been measured in a custom made integrating sphere at several junction temperatures by active cooling and heating with a Peltier element. A spectrum model at 300 K is constructed where the Boltzmann free carrier distribution and carrier temperature are included. Subsequently, the model is extended with the carrier temperature variation, the band gap energy shift, and the nonradiative recombination rate decrease with junction temperature. As a result, the skewness variation, peak frequency shift, and peak value change in the spectrum with temperature can be predicted. The model has been validated by comparing flux and color coordinates of measured and simulated spectra at 340 K junction temperature. In practice, only two spectral flux measurements at different junction temperatures are needed to accurately simulate a single color spectrum at any temperature.

Temperature invariant energy value in LED spectra

“…5 To use LEDs for accurate measurements, precise calibration of their optical and electrical characteristics is required. [6][7][8] The emission spectrum of an LED is generated by electron-hole recombination and can be modelled as a product of the joint density of states of electrons and holes and the Maxwell-Boltzmann distribution.…”

Physics related modeling of power LEDs

“…In a study by A. Keppens et al [7] an alternative approach has been presented for modeling the emission spectrum of a LED, using parameters related to the physical properties of the device. The Boltzmann exponential behavior with carrier temperature variation, bandgap energy shift, and the increase in the nonradiative recombination rate with junction temperature of the semiconductor materials have been explicitly included in the constructed spectrum model.…”

Temperature Effect on the Optical Properties of YAG and Silicate Phosphor-based White Light Emitting Diodes

“…특히 백색 LED의 발광스펙트럼이 온도 등의 외부 변 수에 어떻게 의존하는지를 정확히 분석하는 것은 백색 LED 의 광학적 성능을 개선하는데 있어서 매우 중요한 부분이다. 이러한 분석을 위해 다양한 수학적 함수들이 도입되었고 적 절한 함수의 적용을 통해 스펙트럼의 특징들, 즉 중심파장, 폭 및 비대칭성 등을 성공적으로 분석할 수 있음이 알려져 있다 [8][9][10] . 우리는 이전 연구에서 YAG 및 실리케이트 계 형광체가 적용된 두 종류의 백색 LED의 상온에서의 발광특성이 구동 전류에 따라 어떻게 변하는지를 보고한 바 있다 [11] .…”