Stacked Light-Emitting Device N/P Layers for Efficient Carrier Transfer

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Solution Overview

Problem

Existing stacked light-emitting devices face challenges in ensuring efficient electron and hole transfer due to improperly designed N-type and P-type charge generation layers, leading to reduced light-emitting efficiency and service life.

Innovation Solution

The stacked light-emitting device incorporates a doped binary structure for the N-type and P-type charge generation layers, with specific energy level differences between host and guest materials to prevent reverse transfer of carriers, ensuring stable carrier supply to adjacent light-emitting units.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional charge generation layers are used in stacked light-emitting devices, then device structure is simple, but carrier transfer efficiency is poor and service life is reduced

Engineering Contradiction:

Improveservice lifeVSAvoidcharge generation layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The charge generation layer is segmented into multiple distinct layers (N-type charge generation layer and P-type charge generation layer) with different material compositions and energy levels. Each layer is specifically designed to handle different types of charge carriers (electrons and holes), enabling efficient and selective carrier transport while preventing reverse transfer, thus improving device reliability and service life

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the charge generation layer are assigned different local qualities through the use of N-type and P-type doped materials with distinct energy level characteristics. The N-type layer has higher LUMO energy level to facilitate electron transport, while the P-type layer has lower HOMO energy level for hole transport. This localized differentiation optimizes carrier transfer efficiency in each region while maintaining overall device performance

Inventive Principle:

Principle #3Local quality

2Power

If energy level differences between host and guest materials are not optimized, then material selection is easy, but reverse carrier transfer occurs and light-emitting efficiency decreases

Engineering Contradiction:

Improvelight-emitting efficiencyVSAvoidenergy level design

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The energy level parameters of the host and guest materials are precisely controlled and differentiated. The N-type charge generation layer uses materials with a higher LUMO energy level difference (>0.1 eV) to prevent electron reverse transfer, while the P-type layer uses materials with a lower HOMO energy level difference (>0.3 eV) to prevent hole reverse transfer. These parameter optimizations ensure unidirectional carrier flow and improve light-emitting efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The charge generation layers act as intermediary structures between the electrodes and light-emitting units, mediating the transfer of charge carriers. By introducing N-type and P-type intermediate layers with specific energy level profiles, the device achieves efficient carrier injection and transport while preventing harmful reverse transfer, thus improving overall power efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

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 design enhances light-emitting efficiency and extends the service life of the stacked light-emitting device by maintaining effective electron and hole transfer, thereby improving performance.

Implementation Method 1

the stacked connection layer includes an N-type charge generation layer and a P-type charge generation layer disposed in a stack... an absolute value of a difference between a highest occupied molecular orbital energy level of the second host material and a highest occupied molecular orbital energy level of the first host material is greater than 0.3 electron volts; and an absolute value of a difference between a lowest unoccupied molecular orbital energy level of the second host material and a lowest unoccupied molecular orbital energy level of the first host material is greater than 0.1 electron volts

Methodology Applied

Scientific EffectCharge generation and carrier transfer:

Implementation Method 2

at least two light-emitting units are stacked between the first electrode and the second electrode... the light-emitting units each including a light-emitting layer

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS20250275348A1Light-Emitting Device, Stacked Light-Emitting Device, and Display Substrate

Publication Date: 2025.08.28 BOE TECHNOLOGY GROUP CO LTD

AI summary

A stacked light-emitting device includes a first electrode, a second electrode, at least two light-emitting units, and at least one stacked connection layer. A stacked connection layer is between every two adjacent light-emitting units and includes an N-type charge generation layer and a P-type charge generation layer. The N-type charge generation layer is of a doped binary structure including a first host material and a first guest material; and the P-type charge generation layer is of a doped binary structure including a second host material and a second guest material. An absolute value of difference between HOMO energy level of the second host material and HOMO energy level of the first host material is greater than 0.3 electron volts; and an absolute value of difference between LUMO energy level of the second host material and LUMO energy level of the first host material is greater than 0.1 electron volts.