OLED Emissive Layer with Narrowband Emitter Energy Transfer
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Solution Overview
Problem
Existing organic electroluminescent devices struggle to combine high efficiency, long lifetime, and good color purity, particularly in achieving the BT-2020 and DCPI3 color gamut, due to broad emission spectra and high costs associated with transition metal-based phosphorescence materials.
Innovation Solution
Incorporating a light-emitting layer composed of sublayers containing a host material, a phosphorescence material, a small full width at half maximum (FWHM) emitter, and optionally a thermally activated delayed fluorescence (TADF) material, with each emitter having specific energy levels and narrow emission spectra, to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphorescence materials based on transition metals (e.g., iridium) are used, then high efficiency and long lifetime are achieved, but cost increases due to low abundance and expense of transition metals
Solution Approach 1:
The patent replaces expensive transition metal-based phosphorescence materials with organic fluorescence or TADF emitters that are cheaper and more abundant, accepting that individual emitter molecules have shorter operational lifetimes but achieving device-level longevity through efficient energy management
Solution Approach 2:
The patent introduces an energy pump material (TADF or phosphorescence) as an intermediary that absorbs electrical energy and transfers it to the fluorescence emitter, enabling the cheap organic emitter to achieve high efficiency and long lifetime indirectly through the mediating energy transfer process
2Use of energy by moving object
If phosphorescence materials are used, then high efficiency is achieved, but emission spectrum broadens (FWHM typically larger than 0.25 eV) leading to high losses in out-coupling efficiency for top emitting devices targeting BT-2020 and DCPI3 color gamut
Solution Approach 1:
The patent segments the emission function into two distinct components: an energy pump material that handles energy absorption and transfer, and a separate fluorescence emitter that is specifically optimized for narrow emission spectrum and color purity, allowing each component to be independently optimized for its specific function
Solution Approach 2:
The patent changes the emission mechanism from phosphorescence (broad spectrum) to fluorescence (narrow spectrum), and adjusts the FWHM parameter to be smaller than or equal to 0.25 eV, enabling compatibility with BT-2020 and DCPI3 color gamut requirements while maintaining high efficiency
3Ease of manufacture
If fluorescence or TADF emitters with narrow emission spectrum (FWHM smaller than or equal to 0.25 eV) are used, then color purity and suitability for BT-2020 and DCPI3 color gamut are achieved, but efficiency decreases due to roll-off behaviour at higher luminance and lifetime decreases due to exciton-polaron annihilation or exciton-exciton annihilation
Solution Approach 1:
The patent uses an energy pump material as an intermediary that absorbs electrical energy efficiently and transfers it to the fluorescence emitter, bypassing the efficiency limitations and annihilation losses that would occur if electrical energy were directly converted to light by the fluorescence emitter alone
Solution Approach 2:
The energy pump material performs preliminary energy conversion and preparation, converting electrical energy to excitonic energy in a controlled manner before transferring it to the fluorescence emitter, thereby preventing direct exciton-polaron and exciton-exciton annihilation losses in the emitter
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 proposed configuration achieves a long lifetime, high quantum yield, and narrow emission suitable for the BT-2020 and DCPI3 color gamut, reducing the reliance on expensive transition metals.
Implementation Method 1
Herein, a phosphorescence material and/or an optional TADF material might transfer energy to a small full width at half maximum (FWHM) emitter displaying emission of light.
Implementation Method 2
Incorporating a light-emitting layer composed of sublayers containing a host material, a phosphorescence material, a small full width at half maximum (FWHM) emitter
Implementation Method 3
a thermally activated delayed fluorescence (TADF) material
Implementation Method 4
When a voltage (and electrical current) is applied to an organic electroluminescent device, holes and electrons are injected from an anode and a cathode, respectively. Excitons of high energy are then generated by recombination of the holes and the electrons in a light-emitting layer.
Data Source
AI summary
The present invention relates to a an organic electroluminescent device comprising at least one light-emitting layer B composed of one or more sublayers, wherein the one or more sublayers of the light-emitting layer B as a whole comprise at least one host material HB, at least one phosphorescence material PB, at least one small FWHM emitter SB, and optionally at least one TADF material EB.