OLED Emissive Region Using TADF Mediator for Exciton Harvesting
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Solution Overview
Problem
Existing OLED technologies face challenges in achieving efficient light emission with phosphorescent, TADF, and exciplex systems, often resulting in direct charge trapping, red-shifting issues, and poor spectral overlap, which affect the performance and efficiency of organic light emitting diodes.
Innovation Solution
An OLED architecture incorporating a phosphorescent emitter, a TADF or exciplex emitter, and a fluorescent emitter, where the phosphorescent emitter acts as a sensitizer, enhancing light emission efficiency and spectral characteristics by harvesting singlet and triplet excitons and transferring energy to the fluorescent emitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent emitters are used to harvest triplet excitons, then light emission efficiency is improved, but direct charge trapping occurs and spectral overlap becomes poor
Solution Approach 1:
The patent introduces a TADF emitter as an intermediary between the phosphorescent emitter and the fluorescent emitter. The TADF emitter receives energy from the phosphorescent emitter and transfers it to the fluorescent emitter, preventing direct charge trapping and improving spectral overlap. This mediator approach allows the system to benefit from high efficiency phosphorescent emission while avoiding its harmful direct interaction with fluorescent materials.
Solution Approach 2:
The patent segments the emissive function into three distinct components: phosphorescent emitter, TADF emitter, and fluorescent emitter. Each component performs a specific function in the energy transfer chain, with the phosphorescent emitter harvesting triplet excitons, the TADF emitter acting as an energy bridge, and the fluorescent emitter producing the final light output. This segmentation prevents harmful direct interactions while maintaining high efficiency.
2Use of energy by moving object
If phosphorescent emitters are used to harvest singlet and triplet excitons, then light emission efficiency is improved, but red-shifting issues occur
Solution Approach 1:
The TADF emitter serves as an intermediary that prevents the phosphorescent emitter from directly interacting with the fluorescent emitter, thereby preventing red-shifting. The energy transfer pathway goes through the TADF emitter, which maintains appropriate energy level relationships and prevents the harmful red-shift effect that would occur with direct phosphorescent-fluorescent interaction.
3Use of energy by moving object
If conventional OLED structures are used, then device simplicity is maintained, but light emission efficiency is insufficient
Solution Approach 1:
The patent merges three different emissive materials (phosphorescent, TADF, and fluorescent emitters) into a single emissive region, allowing them to work together in an integrated energy transfer system. This combining approach enables the system to harvest both singlet and triplet excitons while maintaining a relatively simple device structure, as all three components are incorporated into one emissive layer rather than requiring separate layers for each emitter type.
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 improves light emission efficiency, achieves a sharper emission onset, and narrower spectral line shape, with the fluorescent emitter producing at least 65% of the emission, leading to enhanced performance and efficiency in organic light emitting diodes.
Implementation Method 1
The first compound is capable of functioning as a phosphorescent emitter in an OLED at room temperature
Implementation Method 2
the second compound is capable of functioning as a TADF emitter in an OLED at room temperature
Implementation Method 3
the second compound is capable of forming an exciplex with the first compound in an OLED at room temperature
Implementation Method 4
The third compound is a fluorescent compound that functions as an emitter in the OLED of the present disclosure at room temperature
Data Source
AI summary
Provided is an OLED that includes in its emissive region a first compound, a second compound, and a third compound, where the first compound is capable of functioning as a phosphorescent emitter in an OLED at room temperature, the second compound meets at least one of the following conditions:(1) the second compound is capable of functioning as a TADF emitter in an OLED at room temperature; and(2) the second compound is capable of forming an exciplex with the first compound in an OLED at room temperature, and the third compound is a fluorescent compound that functions as an emitter in the OLED of the present disclosure at room temperature.