We demonstrated a 42% luminance enhancement by attaching MLF (Micro Lens Film) on the bottom emitting
OLED. Higher density of MLF extracted more substrate mode to air. We also investigated the compatibility of
MLF and Circular Polarizer (CP) on the bottom emitting OLED. It is found that the efficiency of bottom emitting
OLED with MLF and CP decreases comparing to the reference OLED device, which has CP alone. Simulation
shows that large portion of light is reflected back into CP at the surface of MLF and air. Back reflected light
from MLF is absorbed in CP layer. We have also shown that OLED blur image be enhanced by reducing
substrate thickness.
We report studies on blue and white organic light-emitting devices (OLEDs) based on the deep-blue electrophosphorescent
dye iridium(III)
bis(4',6'-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6). Using high triplet
energy charge transport layers and a dual-emissive-layer structure as well as the p-i-n device structure, we have achieved
external quantum efficiencies of 20% and maximum power efficiency of 36 lm/W in these deep-blue OLEDs. White
OLEDs with a CRI of 79 and a maximum power efficiency of 40 lm/W were also demonstrated by incorporating red and
green phosphorescent dopants together with FIr6.
Organic light emitting devices (OLEDs) have demonstrated the potential for solid state lighting as well as full color
display applications. Use of triplet harvesting phosphorescent materials has led to very high efficiency OLEDs especially
in green and red phosphorescent OLEDs. However in case of blue OLEDs the efficiency achieved is still room for
improvement. Charge balance is a very important factor for achieving high efficiency organic light emitting diodes. In
most OLED devices, hole mobility of hole transport layer is orders of magnitude higher than the electron mobility of
electron transport layer. We study how this affects the charge balance and hence the device performance in the blue
phosphorescent OLEDs with Iridium (III)bis
[(4,6-di-fluorophenyl)- pyridinato-N,C2´] picolinate (FIrpic) emitter.
Charge balance is studied in these devices and the devices are found to be hole dominant. Additionally, effect of charge
balance on device performance is demonstrated with different electron transport layers. Using this approach, a very high
efficiency of 60 Cd/A (50 lm/W) is achieved with
3,5´-N,N´-dicarbazole-benzene (mCP) host.
We have studied the effects of hole transporting layers and electron transporting layers on efficiencies of Iridium(III)bis
[(4,6-di-fluorophenyl)-pyridinato-N,C2'] picolinate (FIrpic) doped 3,5'-N,N'-dicarbazole-benzene (mCP) host blue
PHOLEDs. We found that the device efficiency is very sensitive to the hole transporting materials used and both the
triplet energy and carrier transport properties affect the device efficiency. On the other hand, there is no apparent
correlation between the device efficiency and the triplet energy of the electron transporting material used. Instead, the
device efficiency appears to be determined by the electron mobility of the electron transporting layer only.
In this paper, we demonstrate that the light extraction efficiency of an OLED is a strong function of the location of the
recombination zone and the ratio of the extracted mode to the substrate guided mode varies from 22% to 55%. The large
variation of the extraction efficiency in most OLEDs is the direct result of optical cavity effect present in the devices. In
addition, we show that the light intensity profile varies from a Lambertian shape to a non-Lambertian shape depending
of the device geometry.
Conference Committee Involvement (5)
Organic Light Emitting Materials and Devices XIX
9 August 2015 | San Diego, California, United States
Organic Light Emitting Materials and Devices XVIII
17 August 2014 | San Diego, California, United States
Organic Light Emitting Materials and Devices XVII
25 August 2013 | San Diego, California, United States
Organic Light Emitting Materials and Devices XVI
12 August 2012 | San Diego, California, United States
Display, Solid-State Lighting, Photovoltaics, and Optoelectronics in Energy
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