Spectral dependence of light extraction efficiency of high‐power III‐nitride light‐emitting diodes

Abstract

Using the recently suggested method of processing the data on external quantum efficiency as a function of output optical power, we have estimated the dependence of light extraction efficiency of high‐power light‐emitting diodes (LEDs) on their emission wavelength varied between 425 nm and 540 nm. The extraction efficiency is found to increase with the wavelength from ∼80% to ∼85% in this spectral range and to correlate with the wavelength dependence of reflectivity of the large‐area p‐electrode being the essential unit of the LED chip design. The correlation found identifies the incomplete reflection of emitted light from the electrode as the major mechanism eventually controlling the spectral dependence of the efficiency of light extraction from the LEDs. Spectral dependence of light extraction efficiency of the UX:3TM LED chip: comparison of experiment and modelling results. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Efficiency of True-Green Light Emitting Diodes: Non-Uniformity and Temperature Effects<strong> </strong>

“…The AR of the green LED differs from those studied in [6] in two aspects. First, it consists of five 293 InGaN QWs, which makes band-to-band light absorption quite critical for achieving high LEE.…”

“…As one can see from Figure 6, LEE of the green LED is lower 285 than that of the blue one at all the temperatures. This finding disagrees with the increase in RT LEE 286 from blue to green spectral range observed on SQW-based LEDs [6]. The LEE increasing with wave-287 length was attributed in [6] to temperature dependent optical properties of silver-based p-electrode 288 providing dominant optical losses of the emitted light via its incomplete reflection from the electrode.…”

“…Nevertheless, in LED structures of similar designs, the optical losses have been shown not to 291 change the general trend of LEE to rise with the emission wavelength [6].…”

“…with the ABC-model [6] becomes applicable, providing the LEE value of about 66%. The method used in our study, which implies two ARs to co-exist, gives the value of 68% which is quite close to the above cruder estimate.…”

Superior color rendering with a phosphor‐converted blue‐cyan monolithic light‐emitting diode

“…Using state-ofthe-art chip design developed for high-power LEDs, LEE can be additionally improved, at least, up to ∼82-83% in the spectral range of the dual-wavelength LED operation [36]. Moulding the chip package with silicone lens can give further improvement of LEE, up to 90% [37].…”