OLED Charge Transport Layer Layout for Low Voltage and Color Purity
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Solution Overview
Problem
Existing organic light-emitting elements face issues with increased driving voltage and unintended light emission due to high hole mobility in transport layers, leading to reduced display color gamut.
Innovation Solution
The organic light-emitting element is designed with a charge transport layer comprising three layers, where the first layer has the highest mobility, the second layer has lower mobility than the first, and the third layer has the lowest mobility, with the total thickness of the first two layers being less than the third, reducing charge leakage and unintended light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the hole mobility of the hole transport layer is increased to reduce driving voltage, then the driving voltage is reduced, but current is supplied to adjacent organic light-emitting elements causing unintended light emission
Solution Approach 1:
The charge transport layer is divided into three distinct layers (first, second, and third charge transport layers) with different charge mobility characteristics. This segmentation allows each layer to perform specific functions: the first layer reduces driving voltage through high mobility, while the second and third layers prevent charge leakage through lower mobility, thereby eliminating unintended light emission in adjacent elements.
Solution Approach 2:
Different regions of the charge transport layer are assigned different charge mobility properties. The first charge transport layer has high charge mobility to reduce driving voltage, while the second and third layers have progressively lower mobility to contain charges within the intended pixel region. This local differentiation of properties resolves the contradiction between voltage reduction and preventing charge leakage.
2Power
If a single thick hole transport layer with high hole mobility is used to reduce driving voltage, then the driving voltage is reduced, but charge leakage to adjacent pixels increases
Solution Approach 1:
Instead of using a single thick hole transport layer, the invention segments it into three layers with different thicknesses and mobility characteristics. The first layer (thinner, high mobility) handles voltage reduction, while the second and third layers (thicker, lower mobility) provide charge containment, thereby maintaining reliability while reducing driving voltage.
Solution Approach 2:
The charge transport layer is constructed as a composite structure with three different materials or material compositions, each optimized for specific functions. This composite approach enables simultaneous achievement of low driving voltage and high charge containment reliability that cannot be achieved with a single homogeneous material.
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 effectively reduces driving voltage while minimizing charge leakage and unintended light emission, maintaining color purity in high pixel density displays.
Implementation Method 1
a charge transport layer between the first electrode and the first light-emitting layer, wherein the charge transport layer includes a first charge transport layer, a second charge transport layer, and a third charge transport layer
Data Source
AI summary
The present disclosure provides an organic light-emitting element including a first electrode, an organic compound layer, and a second electrode, wherein the organic compound layer includes a charge transport layer, and the charge transport layer includes a first charge transport layer, a second charge transport layer, and a third charge transport layer in this order, and the first charge transport layer, the second charge transport layer, and the third charge transport layer satisfy Formulas (1) and (2) below:μ1>μ2>μ3 (1)d1+d2<d3 (2)in Formula (1), μ1, μ2, and μ3 are charge mobilities of the first to third charge transport layers, andin Formula (2), d1, d2, and d3 are layer thicknesses of the first to third charge transport layers.