OLED Emitting Layer Spectral Overlap for High Efficiency and Color Purity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic light emitting diodes (OLEDs) face limitations in emitting efficiency due to the involvement of only singlet excitons in fluorescent materials, leading to reduced performance.
Innovation Solution
Incorporation of a delayed fluorescent material and a fluorescent material in a single emitting material layer or adjacent layers, with optimized spectral overlap to enhance energy transfer and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If only fluorescent material is used in the emitting material layer, then the emission spectrum can be narrow, but the emitting efficiency is limited due to involvement of only singlet excitons
Solution Approach 1:
The emitting material layer comprises a composite system of delayed fluorescent material and fluorescent material. The delayed fluorescent material generates both singlet and triplet excitons, while the fluorescent material converts triplet excitons to singlet excitons through energy transfer, enabling both materials to contribute to light emission and improving overall emitting efficiency.
Solution Approach 2:
The delayed fluorescent material acts as an intermediary that generates triplet excitons which are then transferred to the fluorescent material. This intermediary mechanism allows triplet excitons to be utilized indirectly for light emission, converting what would be energy loss into useful emission.
2Use of energy by moving object
If delayed fluorescent material is used to improve emitting efficiency, then triplet excitons can be utilized, but the full width at half maximum (FWHM) increases reducing color purity
Solution Approach 1:
The fluorescent material is introduced to provide a localized narrow emission spectrum in the composite system. While the delayed fluorescent material provides broad emission, the fluorescent material contributes a narrow emission band, resulting in a composite emission spectrum that maintains both high efficiency and acceptable color purity.
Solution Approach 2:
The composite emitting material layer combines the broad emission characteristics of delayed fluorescent material with the narrow emission characteristics of fluorescent material, creating a synergistic system that achieves both high emitting efficiency and improved spectral precision.
3Loss of energy
If the emission spectrum of the first compound and absorption spectrum of the second compound have poor overlap, then the energy transfer efficiency is low, but improving overlap may require compromising other performance parameters
Solution Approach 1:
The molecular structures of the delayed fluorescent material and fluorescent material are optimized to adjust their emission and absorption spectra. By modifying structural parameters such as substituents and conjugation length, the emission spectrum of the delayed fluorescent material is tuned to achieve maximum overlap with the absorption spectrum of the fluorescent material, thereby maximizing energy transfer efficiency.
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 improved emitting efficiency and reduced full width at half maximum (FWHM), resulting in enhanced color purity and performance of OLEDs.
Implementation Method 1
increasing an overlapping ratio between an emission spectrum of the first compound and an absorption spectrum of the second compound
Data Source
AI summary
An organic light emitting diode includes a first electrode; a second electrode facing the first electrode; and a first emitting material layer including a first compound and a second compound and positioned between the first and second electrodes. The emission spectrum of the first compound and the absorption spectrum of the second compound has a relatively large overlapping ratio. An organic light emitting device includes the organic light emitting diode and can be a display device or a lighting device.