Multi-Layer Emission Structure for OLED Stability and Efficiency

Solution Overview

Problem

Current light-emitting devices face challenges in achieving balanced performance metrics such as high luminance, low driving voltage, and long lifespan due to limitations in the stability and optical resonance efficiency of their emission layers.

Innovation Solution

A light-emitting device is designed with a structure that includes a first emission layer and a second emission layer, where each layer comprises specific hosts and dopants represented by Formulae 1, 2, and 3, respectively, optimizing the composition to enhance stability and optical resonance efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional emission layer structure is used, then the device structure is simple, but the stability and optical resonance efficiency are insufficient

Engineering Contradiction:

ImprovestabilityVSAvoidemission layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The emission layer is divided into multiple distinct emission layers (first emission layer, second emission layer, third emission layer) with different host-guest combinations. Each emission layer is segmented to emit specific wavelengths (blue, cyan, green, yellow, orange, red) through controlled dopant selection, resolving the contradiction by achieving high stability through functional segmentation while maintaining manageable structural complexity through systematic design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material systems by combining specific host materials (e.g., mCP, TCTA, TAPC) with guest dopants (e.g., BPhen, Alq3, Ir(ppy)3) in controlled ratios within each emission layer. This composite approach enhances optical resonance efficiency and stability through synergistic material interactions, while the standardized composite structure across multiple layers prevents excessive complexity

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If the emission layer composition is optimized for high luminance, then luminance efficiency improves, but driving voltage increases

Engineering Contradiction:

Improveluminance efficiencyVSAvoiddriving voltage

Core Design Contradiction:

Illumination intensityVSPower

Solution Approach 1:

Each emission layer is assigned specific host-guest material combinations optimized for its target wavelength range. For example, the blue emission layer uses BPhen dopant while the red emission layer uses Ir(ppy)3 dopant. This local optimization of material properties in each layer achieves high luminance efficiency at specific wavelengths without requiring high driving voltage across the entire device, as each layer operates at its optimal electrochemical potential

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent systematically varies key parameters including host-guest concentration ratios (typically 95:5 to 90:10), molecular weight of hosts, HOMO-LUMO energy levels, and layer thicknesses to optimize the balance between luminance efficiency and driving voltage. By adjusting these parameters across different emission layers, the device achieves high overall luminance while maintaining manageable driving voltage through progressive energy level tuning

Inventive Principle:

Principle #35Parameter changes

3Duration of action of stationary object

If stable host-guest combinations are used, then lifespan extends, but optical resonance efficiency decreases

Engineering Contradiction:

ImprovelifespanVSAvoidoptical resonance efficiency

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent employs composite material systems by combining specific host materials (e.g., mCP, TCTA, TAPC) with guest dopants (e.g., BPhen, Alq3, Ir(ppy)3) in controlled ratios within each emission layer. This composite approach enhances optical resonance efficiency and stability through synergistic material interactions, while the standardized composite structure across multiple layers prevents excessive complexity

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent systematically varies key parameters including host-guest concentration ratios (typically 95:5 to 90:10), molecular weight of hosts, HOMO-LUMO energy levels, and layer thicknesses to optimize the balance between luminance efficiency and driving voltage. By adjusting these parameters across different emission layers, the device achieves high overall luminance while maintaining manageable driving voltage through progressive energy level tuning

Inventive Principle:

Principle #35Parameter changes

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 device achieves improved stability, luminance efficiency, and optical resonance, resulting in a low driving voltage and extended lifespan.

Implementation Method 1

Holes provided from the first electrode move toward the emission layer through the hole transport region, and electrons provided from the second electrode move toward the emission layer through the electron transport region. The holes and the electrons, which are carriers, recombine in the emission layer to produce excitons. The excitons transition from an excited state to a ground state, thereby generating light.

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS20230200213A1Light-emitting device and electronic apparatus including the light-emitting device

Publication Date: 2023.06.22 SAMSUNG DISPLAY CO LTD

AI summary

A light-emitting device including an emission layer and an electronic apparatus including the light-emitting device. The emission layer includes a first emission layer and a second emission layer.