Internal quantum efficiency drop induced by the heat generation inside of light emitting diodes (LEDs)

Abstract

The reasons for low output power of AlGaInP Light Emitting Diodes (LEDs) have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies. Two kinds of LEDs with the same active region but different window layers have been fabricated. The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency (EQE) has serious impaction on the internal quantum efficiency (IQE), because the carrier distribution will change with the body temperature increasing due to the heat inside, and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.

56.5: High Temperature Operation Stability Optimization for Flexible Automotive AMOLED by Rational Design

“…We firstly analyzed the heat source of the OLED module. As known to all, the EQE for phosphorescent OLED device was about 20%-30% [2][3][4] while the value for fluorescent OLED device was lower (only about 5%-10%), and the main energy losses for OLED display module included the absorption of optical films with overall transmittance about 38% to 45%, the loss of non-radiation emission and the trap of light in internal of device, as well as the loss of power lines. According to the heat analysis of automotive AMOLED module in our previous work [6] , the emissive energy only took up about 3.7%~4.5% of the input power which meant the proportion of energy convert to heat was as high as more than 90%.…”

“…corresponding to different block as shown in Table 3, it could be seen that the temperature of white block was higher than green monochrome block for about 10 °C, which may cause the deteriorate of green OLED material in white block [2][3][4] . To further affirm this, we conducted long-term high temperature operation with same pattern at 95 °C same as that of white block at 85 °C long-term operation test, and got the luminance delay curve shown in Figure 7.…”

4: Study on the Heat Dissipation of Flexible Vehicle AMOLED Display

“…Mass production of organic light-emitting diode (OLED) had been achieved for consumer electronics such as smart phone, pad and laptop because of the advantages of self-emission, wide color gamut, high contrast ratio, fast response time as well as flexible [1][2][3][4][5][6] . However, due to the lifetime and reliability issues, a few of applications had been reported in vehicle display products [1] .…”

“…As known to all, the maximum internal quantum efficiency (IQE) can reach up to nearly 100% for phosphorescent organic emitters [2] . However, the external quantum efficiency (EQE) for most phosphorescent OLED was only about 20%-30% [3] which meant 70%-80% of the optical energy converted to heat [4] . The lifetime of OLED was decreased by the generated heat [5] , with about 60% shorter lifetime for increase of 10 K [6] .…”

Performance improvement of GaN-based light-emitting diode with a p-InAlGaN hole injection layer

“…InGaN/GaN-based high brightness light-emitting diodes (LEDs) are promising to replace the conventional incandescent and fluorescent lamps due to their inherent higher energy efficiencies and other advantages. [1][2][3][4][5] However, these devices are subjected to a rapid efficiency droop with the injection of an increased current, [6,7] many investigations have suggested that the polarization field is one of the main mechanisms of efficiency droop. [8][9][10][11][12][13] The polarization field leads to a severe reduction in electron-hole wave function overlap (Γ e hh ), consequently resulting in a reduction in the radiative recombination rate and the internal quantum efficiency of the optoelectronic device.…”