Deep-Blue OLEDs with Rec.2020 Blue Gamut Compliance and EQE Over 22% Achieved by Conformation Engineering
Hong-Ji Tan1, Guo-Xi Yang1, Ying-Lan Deng1
1Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Material of Guangdong Province, Shantou University, Guangdong, 515063, P. R. China.
Advanced Materials (Deerfield Beach, Fla.)
|March 2, 2022
Summary
Two novel thermally activated delayed fluorescent (TADF) emitters achieve high-efficiency deep-blue electroluminescence for Rec.2020 standards. Replacing carbon with silicon in TADF molecules suppresses spectral broadening and efficiency roll-off.
Area of Science:
- Organic Chemistry
- Materials Science
- Optoelectronics
Background:
- Achieving high-efficiency deep-blue electroluminescence that meets Rec.2020 standards is crucial for advanced display technologies.
- Thermally activated delayed fluorescence (TADF) emitters offer a promising pathway to overcome the efficiency limitations of traditional organic light-emitting diodes (OLEDs).
- Controlling spectral broadening and efficiency roll-off in deep-blue TADF emitters remains a significant challenge.
Purpose of the Study:
- To develop novel TADF emitters for high-efficiency deep-blue electroluminescence.
- To investigate the impact of structural modifications, specifically replacing a carbon atom with a silicon atom, on emitter performance.
- To achieve deep-blue emission within the Rec.2020 color gamut with suppressed efficiency roll-off.
Main Methods:
- Synthesis and characterization of two novel TADF emitters: TDBA-PAS and TDBA-DPAC, based on an organoboron multi-resonance core.
- Photophysical measurements including photoluminescence quantum yield (PLQY), emission lifetime, and spectral characteristics (FWHM).
- Fabrication and testing of OLED devices using the developed TADF emitters, evaluating external quantum efficiency (EQE) and efficiency roll-off.
Main Results:
- Both TDBA-PAS and TDBA-DPAC exhibit promising deep-blue emission with narrow FWHM (≈50 nm in solution) and high PLQY (up to 92.3%).
- The substitution of a silicon atom for a carbon atom in the TADF structure (TDBA-PAS vs. TDBA-DPAC) leads to enhanced conformational heterogeneities.
- OLEDs utilizing TDBA-PAS demonstrate high maximum EQEs (≈20%), suppressed efficiency roll-off, and color coordinates close to the Rec.2020 blue gamut over a wide doping range (10-50 wt%).
Conclusions:
- The developed TADF emitters show excellent potential for high-performance deep-blue OLEDs.
- Replacing sp3 C with sp3 Si in bulky-group-shielded TADF molecules is an effective strategy to mitigate spectral broadening and efficiency roll-off.
- This research presents a novel design approach for next-generation deep-blue TADF emitters for advanced display applications.
