OLED Emissive Region Segmentation for Quenching Reduction
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Solution Overview
Problem
Conventional OLEDs face challenges in achieving high internal quantum efficiency due to non-radiative decay mechanisms, particularly with triplet excitons, which result in lower luminescent efficiencies and operational stability, especially at room temperature.
Innovation Solution
The use of a plurality of sets of organic layers, each comprising a phosphorescent emissive layer and a neat non-emissive layer, where the emissive layer is not continuous and the energy gaps are not nested, allowing for controlled charge transport and reduced quenching, thereby enhancing phosphorescent emission and maintaining performance comparable to doped devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a doped emissive layer is used to achieve high internal quantum efficiency, then luminescent efficiency is improved, but manufacturing complexity increases due to the need to control doping ratios and deposition rates
Solution Approach 1:
The emissive region is segmented into multiple discrete sets of layers, where each set contains an emissive layer and a non-emissive layer. This segmentation eliminates the need for doping while maintaining high internal quantum efficiency, as each emissive layer can be independently optimized and deposited without complex ratio control.
Solution Approach 2:
Different regions of the emissive structure have distinct properties: emissive layers contain phosphorescent dopants for light emission, while non-emissive layers are neat host materials for charge transport. This local differentiation allows optimization of each layer's function without the complexity of uniform doping throughout the entire emissive region.
2Reliability
If the emissive layer is made continuous to improve charge transport, then electrical conductivity is improved, but quenching increases which reduces luminescent efficiency
Solution Approach 1:
The emissive layer is segmented into discrete, non-continuous layers separated by non-emissive layers. This segmentation prevents quenching by isolating emissive centers while maintaining charge transport through the non-emissive host materials that connect the segmented emissive regions.
Solution Approach 2:
Non-emissive layers act as intermediaries between emissive layers, providing a medium for charge transport while preventing direct interaction between emissive centers that would cause quenching. The non-emissive host materials facilitate charge movement without enabling energy transfer that leads to non-radiative decay.
3Loss of energy
If triplet excitons are utilized to improve internal quantum efficiency, then energy utilization is improved, but non-radiative decay mechanisms increase which reduces operational stability
Solution Approach 1:
The energy gap between the triplet exciton state and the ground state is engineered to be larger than in conventional doped systems. This parameter change reduces the probability of non-radiative decay pathways while maintaining efficient triplet exciton utilization for phosphorescent emission, thereby improving operational stability.
Solution Approach 2:
The emissive layers use composite phosphorescent materials with specific host-guest combinations that optimize triplet exciton management. The non-emissive layers use neat host materials with energy levels designed to prevent non-radiative decay, creating a composite structure that simultaneously achieves high energy utilization and operational stability.
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 achieves comparable performance to conventional doped OLEDs while minimizing quenching and improving manufacturing simplicity by allowing independent control of deposition rates, leading to enhanced luminescent efficiencies and stability.
Implementation Method 1
each comprising an emissive layer and a neat non-emissive layer... allowing for controlled charge transport and reduced quenching, thereby enhancing phosphorescent emission
Implementation Method 2
controlled charge transport
Data Source
AI summary
The present invention provides an OLED with an emissive region comprising a plurality of sets of organic layers, each set comprising a non-continuous emissive layer and a neat non-emissive layer. The present invention also provides an OLED with an emissive region comprising a plurality of sets of organic layers, each set comprising an emissive layer and a neat non-emissive layer, wherein the energy gaps of the emissive layer and the non-emissive layer are not nested. The present invention also provides a method for making OLEDs by depositing on a substrate an anode, a plurality of sets of organic layers, each set comprising an emissive layer and a non-emissive layer wherein each layer is deposited sequentially, and a cathode.