Utilization of a composite hole transporting layer and novel homogeneous double emitting layers for performance improvement and low efficiency roll-off in organic light-emitting diodes

Inverted organic light-emitting diodes (IOLEDs) have a bottom cathode, making them convenient to integrate with the preferred n-type active matrix OLED driving technologies. Furthermore, inverted OLEDs show much better air-stability compared with conventional OLEDs, due to the very reactive and sensitive of alkali doped electron injection layer (EIL) towards ambient oxygen and moisture. For inverted OLEDs, the bottleneck to limit their efficiency and stability is the interface at cathode/EIL and light emitting layer (EML)/charge transporting layer. In this paper, we have investigated the effect of different electron/hole transporting layers on the turn-on voltage, efficiency roll-off and power consumption of inverted orange OLEDs. We found that the device exhibits extremely-low efficiency roll-off and a significant lifetime improvement.

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Efficient organic light-emitting diodes based on iridium(III) complexes containing indolo[3,2,1-jk]carbazole derivatives with narrow emission bandwidths and low efficiency roll offs

Journal of Materials Chemistry C ◽

10.1039/d1tc01449h ◽

2021 ◽

Author(s):

Xiang-Ji Liao ◽

Jin-Jun Zhu ◽

Li Yuan ◽

Zhi-Ping Yan ◽

Xu-Feng Luo ◽

...

Keyword(s):

Light Emitting Diodes ◽

Organic Light Emitting Diodes ◽

Light Emitting ◽

Carbazole Derivatives ◽

Highly Efficient ◽

Organic Light ◽

Low Efficiency ◽

Narrow Emission

In this work, two cyclometalated ligands 2-(pyridin-2-yl)indolo[3,2,1-jk]carbazole (pyidcz) and 2-(4-(trifluoromethyl)pyridin-2-yl)indolo[3,2,1-jk]carbazole (tfpyidcz) using indolo[3,2,1-jk]carbazole unit were synthesized for highly efficient iridium(III) complexes (pyidcz)2Ir(tmd) and (tfpyidcz)2Ir(tmd) (tmd = 2,2,6,6-tetramethyl-3,5-heptanedione). The two Ir(III)...

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High efficiency blue organic light-emitting diodes with below-bandgap electroluminescence

Nature Communications ◽

10.1038/s41467-021-25135-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Maria Vasilopoulou ◽

Abd. Rashid bin Mohd Yusoff ◽

Matyas Daboczi ◽

Julio Conforto ◽

Anderson Emanuel Ximim Gavim ◽

...

Keyword(s):

High Efficiency ◽

Light Emitting Diodes ◽

High Mobility ◽

Organic Light Emitting Diodes ◽

Triplet Energy ◽

Material Interface ◽

Light Emitting ◽

Thermally Activated ◽

Organic Light ◽

Hole Transporting

AbstractBlue organic light-emitting diodes require high triplet interlayer materials, which induce large energetic barriers at the interfaces resulting in high device voltages and reduced efficiencies. Here, we alleviate this issue by designing a low triplet energy hole transporting interlayer with high mobility, combined with an interface exciplex that confines excitons at the emissive layer/electron transporting material interface. As a result, blue thermally activated delay fluorescent organic light-emitting diodes with a below-bandgap turn-on voltage of 2.5 V and an external quantum efficiency (EQE) of 41.2% were successfully fabricated. These devices also showed suppressed efficiency roll-off maintaining an EQE of 34.8% at 1000 cd m−2. Our approach paves the way for further progress through exploring alternative device engineering approaches instead of only focusing on the demanding synthesis of organic compounds with complex structures.

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