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A high performance inverted green emission organic light emitting diode with a maximum external quantum efficiency of 20% and a maximum power efficiency of 80 lm/W was realized by properly selecting an electron transporting material to have no energy barrier for electron injection between the n-doped electron transporting layer (n-ETL) and the ETL. Based on the energy levels and the current density–voltage characteristics of electron only devices, we demonstrate that the interface between an n-ETL and an ETL even in homo-junction is as important as the interface between the cathode and the n-ETL for efficient electron injection into an emitting layer.

Corrugated organic light emitting diodes are fabricated on photonic crystal substrates patterned using UV nanoimprint lithography process at room-temperature and low-pressure. Forty-nine percentage enhancement of light extraction was achieved even with the very low corrugation depth of 50 nm. The power efficiency of the corrugated OLEDs was even further improved by 93% compared to the OLED with a planar structure. Finite difference time domain (FDTD) analyses indicated that the Bragg-reflection by the corrugated metallic mirror plays dominant role in the enhancement of extraction efficiency in the corrugated structure and extraction efficiency can be further improved if corrugation depth is increased to 100 nm.

A host material containing tetraphenylsilane moiety, 9-(4-triphenylsilanyl-(1,1′,4,1′′)-terphenyl-4′′-yl)-9 H -carbazole (TSTC), was synthesized for green phosphorescent organic light emitting diodes. The tetraphenylsilane moiety was introduced to provide high triplet energy level, thermal and chemical stability, and glassy properties leading to high efficiency and operational stability of the devices. Ir(ppy) 3 based OLEDs using the TSTC host and DTBT (2,4-diphenyl-6-(4′-triphenylsilanyl-biphenyl-4-yl)-1,3,5-triazine) hole blocking layer (HBL) resulted in the maximum external quantum efficiency of 19.8% and the power efficiency of 59.4 lm/W. High operational stability with a half lifetime of 160,000 h at an initial luminance of 100 cd/m 2 was achieved from an electrophosphorescent device using TSTC host and BAlq HBL.