Hybrid warm-white organic light-emitting device based on tandem structure

Area of Science:

• Organic electronics
• Solid-state lighting
• Materials science

Background:

• Organic light-emitting devices (OLEDs) are crucial for displays and lighting.
• Achieving stable, efficient, and pure white emission in OLEDs remains a challenge.
• Tandem device architectures offer potential for improved performance.

Purpose of the Study:

• To develop an efficient hybrid tandem warm white OLED.
• To achieve extremely stable color purity in the forward direction.
• To investigate the mechanisms behind efficiency roll-off and color stability.

Main Methods:

• Fabrication of a charge generation unit (CGU) using 1, 4, 5, 8, 9, 11-Hexaazatriphenylene-hexacarbonitrile with LiF/Al bilayers.
• Characterization of the tandem white OLED's efficiency and color coordinates at various luminance and current densities.
• Optical simulations and application of the triplet-polaron quenching (TPQ) model to analyze performance.

Main Results:

• The hybrid tandem white OLED achieved maximum efficiencies of 37.3 cd/A and 23.3 lm/W.
• High efficiencies of 34.4 cd/A and 17 lm/W were maintained at 1000 cd/m² luminance.
• Minimal variation in Commission Internationale de l'Eclairage (CIE) coordinates (0.007, 0.003) was observed with increasing current density.
• The study identified the origin of alleviated efficiency roll-off using the TPQ model.

Conclusions:

• An efficient and stable hybrid tandem warm white OLED was successfully realized.
• The proposed charge generation unit facilitates easy fabrication and excellent device performance.
• Understanding color variation and efficiency roll-off mechanisms is key for future OLED development.