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Efficient red electroluminescent devices with sterically hindered phosphorescent platinum(II) Schiff base complexes
Liang Zhou1, Chun-Lam Kwong, Chi-Chung Kwok
1State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (P.R. China).
Chemistry, an Asian Journal
|August 23, 2014
Summary
Sterically hindered platinum(II) Schiff base complexes enable efficient red organic light-emitting diodes (OLEDs). A novel device design with an iridium(III) codop significantly reduces efficiency roll-off, achieving a long operational lifetime.
Area of Science:
- Materials Science
- Organic Electronics
- Photochemistry
Background:
- Platinum(II) Schiff base complexes are investigated for their photoluminescent properties.
- Organic light-emitting diodes (OLEDs) face challenges with efficiency roll-off and limited operational lifetimes.
- Steric hindrance in ligands can influence the photophysical properties and solid-state packing of metal complexes.
Purpose of the Study:
- To synthesize and characterize sterically hindered platinum(II) Schiff base complexes for red light emission.
- To fabricate and optimize OLED devices utilizing these complexes as emissive materials.
- To investigate strategies for mitigating efficiency roll-off and enhancing device stability.
Main Methods:
- Synthesis and characterization of platinum(II) Schiff base complexes, including complex 4.
- Fabrication of OLED devices with single or double emissive layers (EMLs).
- Codoping of an iridium(III) complex into the electron-dominant EML as a deep electron trapper.
- Evaluation of device performance, including current efficiency, power efficiency, external quantum efficiency (EQE), and operational lifetime (LT50).
Main Results:
- Complex 4 exhibits red emission with a quantum yield of 0.29 in thin films and a low self-quenching rate constant.
- The fabricated red-emitting OLEDs achieved high efficiencies: 20.43 cd/A (current), 18.33 lm/W (power), and 11.7% (EQE).
- High efficiencies were maintained at high brightness (1000 cd/m²), with current efficiency of 14.69 cd/A and EQE of 8.3%.
- A projected lifetime (LT50) of 18,000 hours was achieved, attributed to the bulky 3D structure of the ligand and the device design.
Conclusions:
- Sterically hindered platinum(II) Schiff base complexes are promising for efficient red OLEDs.
- The proposed device architecture, incorporating an iridium(III) codop as an electron trapper, effectively suppresses efficiency roll-off.
- The bulky ligand structure contributes to improved device stability and longevity, paving the way for practical applications.
