We have studied the effects of the hole transporting layers and electron transporting layers on the device efficiencies of iridium(III) bis[(4,6-di-fluorophenyl)-pyridinato-N,C2′] picolinate (FIrpic) doped 3,5′−N,N′-dicarbazole-benzene (mCP) host blue phosphorescent organic light emitting diodes. 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 is affected by the electron mobility of the electron transporting layer only.

We have demonstrated a substantial enhancement in the efficiency of iridium (III) bis[(4,6-di-fluorophenyl)-pyridinate-N,C2′]picolinate based blue phosphorescent organic light-emitting devices (PHOLEDs). The efficiencies of PHOLEDs with conventional electron transport materials are low due to their low electron mobilities as well low triplet energies. High triplet energy electron transporting material with high electron mobility was used as a hole blocker to achieve efficient exciton confinement and good charge balance in the device thereby achieving a high current efficiency of 49cd∕A and an external quantum efficiency of 23%.

We report a significant improvement in the efficiency of deep-blue phosphorescent organic light-emitting devices based on the electrophosphorescent dye bis(4′,6′-difluorophenylpyridinato)tetrakis (1-pyrazolyl) borate (FIr6). Using 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) as the hole transport layer (HTL), we achieved a maximum external quantum efficiency of ηEQE=(18±1)%, which is approximately 50% higher than ηEQE=12% in a previously reported device with bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl as the HTL. The maximum luminous power efficiency was also improved from (14±1)lm∕W to (18±1)lm∕W. We attribute this efficiency improvement to the enhanced electron and exciton confinement provided by TAPC.

The light extraction efficiency in organic light-emitting devices (OLEDs) is enhanced by up to 2.6 times when a close-packed, hemispherical transparent polymer microlens array (MLA) is molded on the light-emitting surface of a top-emitting device. The microlens array helps to extract the waveguided optical emission in the organic layers and the transparent top electrode, and can be manufactured in large area with low cost.

We demonstrate high efficiency white organic light-emitting devices with two adjacent emissive layers each doped with three phosphorescent emitters (blue, green, and red). Efficient charge and exciton confinement is realized by employing charge transport layers with high triplet energy, leading to a maximum external quantum efficiency of (19±1)%. Using the p-i-n device structure, we have achieved a peak power efficiency of (40±2) lm/W and (36±2) lm/W at 100 cd/m2, a color rendering index of 79, and Commission Internationale de L’Eclairage coordinates of (0.37, 0.40) for the white light emission.