Hybrid OLED Interlayer for Triplet Quenching
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Solution Overview
Problem
Hybrid organic light-emitting diodes (OLEDs) with two emitting layers face challenges in achieving high efficiency and long operating lifetime while maintaining accurate white color location and stability, particularly due to the low triplet level of common blue-phosphorescent emitter materials, which lead to triplet exciton quenching and inefficient charge balance.
Innovation Solution
Incorporating a non-emitting interlayer between the phosphorescent and fluorescent emitter layers, where at least one of the emitting layers comprises a dopant in a mixture of two matrix materials, to prevent triplet exciton quenching and ensure balanced charge transport, allowing for adjustable and reproducible white color emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a non-emitting interlayer is introduced between the fluorescent and phosphorescent emitter layers to prevent triplet exciton quenching, then the efficiency is improved, but the device complexity increases
Solution Approach 1:
A non-emitting interlayer comprising a hole-transport material and an electron-transport material is introduced between the fluorescent blue emitter layer and the phosphorescent yellow-to-orange emitter layer. This interlayer acts as an intermediary that prevents direct contact between the emitter layers, thereby preventing triplet exciton quenching while maintaining efficient charge transport and balance.
2Loss of energy
If blue-phosphorescent emitters are used to achieve high efficiency, then the efficiency is improved, but the operating lifetime is reduced due to low triplet level causing triplet exciton quenching
Solution Approach 1:
The non-emitting interlayer with appropriate triplet energy level acts as a protective barrier that prevents triplet excitons from being quenched by the blue emitter layer, thereby extending the operating lifetime while maintaining the efficiency benefits of phosphorescent emitters.
Solution Approach 2:
The interlayer is designed with specific material properties (hole-transport and electron-transport characteristics) and appropriate thickness (typically 5-20 nm) to optimize both efficiency and lifetime performance without significantly impacting the overall device structure.
3Loss of energy
If an interlayer is introduced to prevent triplet exciton quenching, then the efficiency is improved, but the color location control becomes more difficult
Solution Approach 1:
By adjusting the thickness of the non-emitting interlayer and the doping concentrations of the hole-transport and electron-transport materials, the color location of the white-emitting OLED can be precisely controlled while maintaining high efficiency and preventing triplet exciton quenching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly enhances the efficiency and operating lifetime of the OLEDs while allowing for precise control of the color location, maintaining stability across varying luminances.
Implementation Method 1
one emitting layer comprises a phosphorescent compound
Implementation Method 2
the other emitting layer comprises a fluorescent compound
Implementation Method 3
white-emitting organic electroluminescent devices
Data Source
AI summary
The present invention relates to white-emitting organic electroluminescent devices which have a fluorescent emitter layer and a phosphorescent emitter layer.