Estimating the average junction temperature of AlGaInP LED arrays by spectral analysis

This study proposes a practical method to estimate the junction temperature of AlGaInP LED arrays based on the shift of the center wavelength at full width at half maximum (FWHM). For AlGaInP LEDs, the peak wavelength will shift with increases in junction temperature. The shift rate depends on the Al doping level, which means for different AlGaInP LEDs with various peak wavelengths, the shift rate of the peak wavelengths will be different. When the light output of several LEDs with different peak wavelength is mixed, the peak area of the spectrum broadens and flattens and it is difficult to accurately estimate the peak wavelength shift. The center wavelength at FWHM, however, shows good linearity with junction temperature; moreover, this linearity is much better compared with the mixed peak wavelength for the AlGaInP array. ► Peak wavelength-to-junction temperature linearity is weak for AlGaInP LED arrays. ► There is a linear relationship between junction heating and increasing FWHM. ► For FWHM, higher wavelength side shifts faster than lower side with increased heat. ► Center wavelength of FWHM can predict junction temperature of AlGaInP LED arrays.