OLED Emissive Layer Doping for Blue Efficiency and Lifespan
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Solution Overview
Problem
Existing blue light emitting layers in organic light emitting diode (OLED) displays suffer from low efficiency and reduced lifespan, making it difficult to achieve both improved efficiency and lifespan in full color displays.
Innovation Solution
An organic light emitting device with a light emitting layer containing different kinds of dopants, where energy is transferred to a thermally activated delayed fluorescence (TADF) dopant, facilitating both fluorescence and thermally activated delayed fluorescence (TADF) emissions, thereby enhancing efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fluorescent or phosphorescent dopants are used in blue light emitting layers, then color emission is achieved, but efficiency and lifespan are reduced
Solution Approach 1:
The dopant system is segmented into multiple components: a primary dopant (fluorescent or phosphorescent) and a TADF dopant with specific energy level relationships. This segmentation allows each dopant to perform specialized functions - the primary dopant provides initial emission while the TADF dopant recycles triplet excitons, resolving the contradiction between efficiency and lifespan by distributing functional responsibilities across different dopant species.
Solution Approach 2:
The invention uses a composite dopant system combining materials with different luminescence characteristics (fluorescent, phosphorescent, and TADF materials) in a single light emitting layer. This composite approach enables simultaneous achievement of high efficiency (through TADF triplet recycling) and long lifespan (through reduced triplet exciton accumulation) that cannot be achieved with single-material dopants alone.
2Use of energy by moving object
If energy is transferred to a TADF dopant, then internal quantum efficiency reaches 100%, but device complexity increases
Solution Approach 1:
The invention optimizes specific energy level parameters - particularly ensuring the T1 energy level of the TADF dopant is lower than or equal to the S1 energy level, and the T1 level is lower than the primary dopant's T1 level. These parameter changes enable spontaneous energy transfer and triplet exciton recycling without requiring complex external control mechanisms, achieving 100% internal quantum efficiency through carefully selected material parameters rather than complex device architecture.
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
The solution achieves high internal quantum efficiency of 100% and extended lifespan by minimizing triplet exciton recombination and annihilation, resulting in stable, efficient, and uniform color emission across the visible spectrum.
Implementation Method 1
a first dopant to which energy is transferred from the host and a second dopant to which energy is transferred from the host and the first dopant
Implementation Method 2
A thermally activated delayed fluorescence (TADF) may be generated through a reverse intersystem crossing transfer from the triplet excited state to the singlet excited state in the second dopant
Implementation Method 3
A thermally activated delayed fluorescence (TADF) may be generated through a reverse intersystem crossing transfer from the triplet excited state to the singlet excited state in the second dopant
Implementation Method 4
minimizing triplet exciton recombination and annihilation
Implementation Method 5
minimizing triplet exciton recombination and annihilation
Data Source
AI summary
Disclosed are display devices including a substrate having a plurality of subpixels, a thin film transistor in each of the subpixels, an organic light emitting device including at least one light emitting layer in each of the subpixels connected to the thin film transistor, and a color filter corresponding to each of the subpixels and disposed on a second electrode of the organic light emitting device, wherein the at least one light emitting layer as a single layer includes at least one host, a first dopant as a phosphorescent dopant and a second dopant as a fluorescent dopant. In the light emitting layer, energy is transferred from a host and other dopants to one dopant by energy transfer system, thus it is possible to increase luminous efficacy of a single color and to increase lifetime of emission.