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Normalized EL spectra of the yellow (dotted lines), orange (dashed lines), and red (solid lines) AlGaInP LEDs at three duty cycles (0.03, 0.5, and 1). The arrows indicate the blueshift of the peak wavelength of the LED with decreasing duty cycle.
(a) The peak wavelength shift and (b) bandwidth broadening of the studied AlGaInP LEDs as a function of the duty cycle. The bandwidths of the LEDs have been calculated on the basis of the full width at half maximum.
(a) The peak wavelength shifts in calibration measurement of the junction temperature and (b) the junction temperatures under the PWM control for the studied AlGaInP LEDs. Junction temperature coefficient of the peak wavelength and duty cycle coefficient of the junction temperature for each LED are shown.
(a) Illustration of the carrier temperature determination of the red AlGaInP LED at duty cycles of 0.03 and 1. The solid lines show fits to Eq. (2). Obtained values for the carrier temperature of the LED at given duty cycles are also displayed. (b) Change of the carrier temperature of the studied AlGaInP LEDs as a function of the duty cycle.
chromaticity coordinates of three AlGaInP LEDs at duty cycles of 0.03, 0.2, 0.5, 0.8, and 1.0 in CIE 1976 uniform chromaticity scale diagram. The arrows show the direction and magnitude of the chromaticity change of the studied LEDs as their duty cycle decreases. The inset illustrates the chromaticity change of the yellow and orange AlGaInP LEDs.
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