Highly efficient organic light emitting diodes formed by solution processed red emitters with evaporated blue common...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Solution-processed phosphorescent organic light-emitting diodes (PHOLEDs) offer a cost-effective alternative to vacuum deposition.
• Efficient confinement of triplet excitons within the emission layer (EML) is crucial for high-performance PHOLEDs.
• Small molecular hosts without flexible spacers are desirable for improved device stability.

Purpose of the Study:

• To develop highly efficient solution-processed red PHOLEDs.
• To achieve efficient triplet exciton confinement using a blue common layer and bipolar exciton blocking layer.
• To investigate the performance of PHOLEDs utilizing small molecular hosts without flexible spacers.

Main Methods:

• Fabrication of red PHOLEDs using solution processing techniques.
• Implementation of a blue common layer structure with a bipolar exciton blocking layer.
• Composition of the EML with a specific ratio of n-type host (NH) and p-type host (PH), doped with a red phosphorescent dopant (RD).

Main Results:

• Achieved record efficiencies for solution-processed small molecular red PHOLEDs: 23.4 cd/A (current efficiency), 13.6 lm/W (power efficiency), and 19% external quantum efficiency at 1000 cd/m².
• Demonstrated effective confinement of triplet excitons within the red EML.
• Utilized host molecules lacking flexible spacers, contributing to enhanced device stability.

Conclusions:

• The developed blue common layer structure effectively confines triplet excitons in solution-processed red PHOLEDs.
• The study presents a new benchmark for efficiency in small molecule red PHOLEDs fabricated via solution processing.
• The absence of flexible spacers in host molecules leads to improved device stability, paving the way for practical applications.