Organic EL Element with Segmented Luminescent Layers

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Solution Overview

Problem

Existing organic EL elements face challenges in achieving balanced white-light emission and long-life operation at low voltage due to inefficiencies in luminescent layer stacking and host material selection, leading to increased driving voltage and reduced luminous efficiency.

Innovation Solution

The organic EL element is designed with a specific stacking order of luminescent layers, where the anode, red, blue, and green luminescent layers are adjacent, and each layer contains a distinct host material, optimizing energy transfer and reducing energy loss, with the red layer closer to the anode to trap electrons and enhance luminous efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional luminescent layer stacking is used, then manufacturing is simpler, but driving voltage increases and luminous efficiency decreases

Engineering Contradiction:

Improveluminous efficiencyVSAvoidenergy loss in luminescent layers

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The invention divides the white light-emitting luminescent layer into three separate color luminescent layers (red, green, and blue) with distinct host materials. Each layer is optimized for its specific wavelength range, preventing energy loss from mismatched energy levels and improving overall luminous efficiency while maintaining balanced color emission.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each luminescent layer is assigned a specific host material optimized for its color emission characteristics. The red layer uses host material A, the green layer uses host material B, and the blue layer uses host material C, allowing each layer to operate at optimal energy levels for its specific function, thereby reducing energy loss.

Inventive Principle:

Principle #3Local quality

2Power

If conventional luminescent layer stacking is used, then device structure is simpler, but operating voltage increases

Engineering Contradiction:

Improvedriving voltageVSAvoidluminescent layer structure

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

By segmenting the white light-emitting layer into three separate color layers with different host materials, the invention creates more favorable energy level gradients for charge carrier injection and transport. This segmentation enables lower driving voltage operation despite the increased structural complexity of having three distinct luminescent layers.

Inventive Principle:

Principle #1Segmentation

3Illumination intensity

If white light-emitting luminescent layer is used, then device structure is simpler, but emission balance is poor

Engineering Contradiction:

Improvewhite light emission balanceVSAvoidluminescent layer configuration

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The invention segments the white light emission function into three separate color-emitting luminescent layers, each with host materials optimized for its specific wavelength. This allows independent optimization of emission intensity for red, green, and blue colors, achieving balanced white light emission that cannot be achieved with a single white light-emitting layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each luminescent layer is given local quality through specific host material selection (host material A for red, host material B for green, host material C for blue), allowing each layer to emit its color at optimal intensity. This local optimization enables overall balanced white light emission across the visible spectrum.

Inventive Principle:

Principle #3Local quality

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 enables the organic EL element to operate at a low voltage while maintaining balanced white-light emission and improving durability by reducing energy loss and enhancing electron and hole transport, resulting in high luminous efficiency and extended lifespan.

Implementation Method 1

an organic EL element includes an anode acting as a light-reflective electrode, a first luminescent layer containing a red dopant, a second luminescent layer containing a blue dopant, a third luminescent layer containing a green dopant, and a cathode

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS10937979B2Organic el element, and display device, imaging apparatus, lighting device, and movable body including the same

Publication Date: 2021.03.02 CANON KK

AI summary

An organic EL element includes a first electrode, a first luminescent layer, a second luminescent layer, a third luminescent layer, and a second electrode, in this order. The second luminescent layer is in contact with the first luminescent layer and the third luminescent layer. The first luminescent layer contains a red dopant and a first host material. The second luminescent layer contains a blue dopant and a second host material, and the third luminescent layer contains a green dopant and the second host material. The second host material is different from the first host material.