OLED Mixed Electron Transport Layers Temperature Stability

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Solution Overview

Problem

Organic light emitting devices (OLEDs) face challenges in maintaining efficiency and longevity due to significant changes in performance with temperature variations, leading to reduced emission efficiency and shorter lifespan.

Innovation Solution

The implementation of an organic light emitting device structure that includes a first electrode, a hole transport region, an emission layer, an electron transport region with a mixed electron transport layer, and a second electrode, where the electron transport region features a first mixed electron transport layer and a second mixed electron transport layer with specific ratios of electron transport compounds, optimizing the energy band gaps for efficient electron and hole injection and recombination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional electron transport layer structure is used, then the device structure is simple, but the efficiency changes significantly with temperature and the lifespan is reduced

Engineering Contradiction:

ImprovelifespanVSAvoidelectron transport region structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The electron transport region is divided into three distinct layers: an electron transport layer, a first mixed electron transport layer, and a second mixed electron transport layer. Each layer has specific thickness and composition ratios that segment the electron transport function into multiple stages, reducing efficiency changes with temperature and extending device lifespan.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first and second mixed electron transport layers use composite materials formed by mixing electron transport compounds with specific weight ratios (first mixed layer: 30-70 wt% first compound and 70-30 wt% second compound; second mixed layer: 40-60 wt% first compound and 60-40 wt% second compound). These composite material compositions optimize electron transport while maintaining stability across temperature variations.

Inventive Principle:

Principle #40Composite materials

2Productivity

If the electron transport layer uses a single compound, then the manufacturing process is simple, but the electron and hole injection efficiency is insufficient

Engineering Contradiction:

Improveelectron and hole injection efficiencyVSAvoidmanufacturing process complexity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

Different layers within the electron transport region have different material compositions and properties optimized for their specific functions. The electron transport layer, first mixed layer, and second mixed layer each have tailored compound ratios and thicknesses (electron transport layer: 50-150 nm, first mixed layer: 100-200 nm, second mixed layer: 100-200 nm) to create local quality variations that enhance overall injection efficiency.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the compositional parameters of the electron transport region by using multiple compounds in specific weight ratios across different layers. The first electron transport compound and second electron transport compound are mixed in varying proportions (30-70/70-30 in first mixed layer, 40-60/60-40 in second mixed layer) to optimize energy band gaps and improve electron and hole injection efficiency.

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

This configuration reduces efficiency changes with temperature and extends the lifespan of OLEDs by facilitating easier electron and hole injection, resulting in high efficiency and prolonged device life.

Implementation Method 1

The electron transport region includes an electron transport layer on the emission layer, a first mixed electron transport layer on the electron transport layer, and a second mixed electron transport layer on the first mixed electron transport layer

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 2

holes and electrons injected from a first electrode and a second electrode are recombined in an emission layer, and excitons obtained by the combination of the injected holes and electrons emit light during the transition thereof from an excited state to a ground state

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS10177334B2Organic light emitting device and display device having the same

Publication Date: 2019.01.08 SAMSUNG DISPLAY CO LTD

AI summary

An organic light emitting device includes a first electrode, a hole transport region provided on the first electrode, an emission layer provided on the hole transport region, an electron transport region provided on the emission layer, and a second electrode provided on the electron transport region. The electron transport region includes an electron transport layer provided on the emission layer, a first mixed electron transport layer provided on the electron transport layer, and a second mixed electron transport layer provided on the first mixed electron transport layer. The first mixed electron transport layer includes a first electron transport compound and a second electron transport compound different from the first electron transport compound mixed at a first ratio. The second mixed electron transport layer includes the first electron transport compound and the second electron transport compound mixed at a second ratio different from the first ratio.