Improving the uniformity of top emitting organic light emitting diodes using a hybrid electrode structure

Mina Riahi, Kou Yoshida, Hassan Hafeez, Ifor D. W. Samuel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Some applications of organic light-emitting diodes (OLEDs) require large area, high light output, and high uniformity. It is difficult to achieve these attributes simultaneously because of voltage drops in the contacts, which cannot easily satisfy high optical transparency and electrical conductivity simultaneously. In large area OLEDs, thin electrodes with high sheet resistance induce voltage drops across the devices, leading to non-uniform distribution of light. However, thick electrodes with low sheet resistance decrease the light output due to low transmittance. To overcome this trade-off, a multilayer hybrid electrode based on Ag (20 nm)/WO3/Ag (20 nm)/WO3 is designed to obtain high electrical conductance with low optical loss. Compared to conventional devices using a single Ag (40 nm) top electrode, there is a considerable increase in the external quantum efficiency (EQE) of the device using this electrode (from 11.5% to 25.5% at 1000 cd m−2), while maintaining similar sheet resistance. In addition, a large area (≈57 cm2) OLED with the hybrid electrode demonstrates a luminance uniformity of 77% as compared to a device using single silver electrode with uniformity of 66%. Therefore, the proposed Ag/WO3/Ag/WO3 hybrid electrode is a promising choice for the fabrication of efficient and uniform large-area OLEDs.
Original languageEnglish
Article number2300675
Number of pages7
JournalAdvanced Electronic Materials
Volume10
Issue number1
Early online date31 Oct 2023
DOIs
Publication statusPublished - Jan 2024

Keywords

  • Transparent conductor
  • Large area OLED
  • Sheet resistance

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