QLED Hole Injection Layer Energy Alignment for Charge Balance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current QLED device structures based on OLED theoretical systems struggle to simultaneously improve photoelectric efficiency and lifetime performance, as they often lead to reduced device lifetime due to charge accumulation and inefficiencies in hole injection.

Innovation Solution

A photoelectric device structure is designed with specific energy level differences between hole transport and hole injection layers, such as |ΔEHTL-HIL| ≤ 0.2 eV, to reduce energy barriers and prevent charge accumulation, and a core-shell quantum dot structure with ΔEEML-HTL ≥ 0.5 eV to balance hole and electron injection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional QLED device structures based on OLED theoretical systems are used, then photoelectric efficiency can be improved, but device lifetime is significantly reduced due to charge accumulation and hole injection inefficiencies

Engineering Contradiction:

Improvephotoelectric efficiencyVSAvoiddevice lifetime

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the energy level difference between hole transport layer and hole injection layer to be ≤0.2 eV. This specific parameter adjustment optimizes hole injection efficiency while preventing charge accumulation, thereby simultaneously improving photoelectric efficiency and device lifetime without relying on conventional OLED-based structures

Inventive Principle:

Principle #35Parameter changes

2Reliability

If energy level difference between hole transport layer and hole injection layer is large, then charge accumulation is reduced, but hole injection efficiency deteriorates

Engineering Contradiction:

Improvecharge accumulation preventionVSAvoidhole injection efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent resolves this contradiction by establishing an optimal parameter range for the energy level difference (≤0.2 eV) between hole transport layer and hole injection layer. This precise parameter control ensures sufficient hole injection efficiency while preventing excessive charge accumulation, achieving balance between the two opposing requirements

Inventive Principle:

Principle #35Parameter changes

3Productivity

If quantum dot light-emitting layer is directly connected to hole transport layer with large energy difference, then electron-hole recombination efficiency improves, but interface damage occurs due to charge accumulation

Engineering Contradiction:

Improveelectron-hole recombination efficiencyVSAvoidinterface damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a hole injection layer as an intermediary between the anode and hole transport layer. This intermediate layer acts as a buffer that facilitates smooth charge transition, improving electron-hole recombination efficiency while preventing direct interface damage between quantum dot light-emitting layer and hole transport layer

Inventive Principle:

Principle #24Intermediary (Mediator)

4Loss of energy

If high efficiency QLED structure is designed following OLED principles, then luminous efficiency increases, but device stability and lifetime are compromised

Engineering Contradiction:

Improveluminous efficiencyVSAvoiddevice stability

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The patent deviates from conventional OLED-based QLED structures by implementing specific parameter changes: energy level difference between hole transport and hole injection layers ≤0.2 eV, and energy level difference between quantum dot light-emitting layer and hole transport layer ≥0.5 eV. These parameter adjustments achieve high luminous efficiency while maintaining device stability and longevity

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 approach enhances hole injection efficiency, reduces irreversible damage, and prolongs the device's lifetime by maintaining a stable and balanced carrier injection, leading to improved luminous efficiency and extended operational life.

Implementation Method 1

an absolute value of a difference between a maximum energy level of valence band of a hole transport material in the hole transport layer and a work function of a first hole injection material in the first hole injection layer is smaller than or equal to 0.2 eV

Methodology Applied

Scientific EffectEnergy level alignment:

Implementation Method 2

a quantum dot light-emitting layer arranged on the hole transport layer

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS20240040816A1Photoelectric devices

Publication Date: 2024.02.01 TCL TECHNOLOGY GROUP CORPORATION

AI summary

A photoelectric device, which includes an anode, a first hole injection layer, a hole transport layer, a quantum dot light-emitting layer, and a cathode arranged in sequence, and an absolute value of a difference between a maximum energy level of valence band of a hole transport material in the hole transport layer and a work function of a first hole injection material in the first hole injection layer is smaller than or equal to 0.2 eV.