Quantum Dot Device Non-Emissive Layer Electron Mobility

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Solution Overview

Problem

Conventional quantum dot devices face performance limitations due to unbalanced mobility of holes and electrons, leading to reduced luminous efficiency and shortened lifespan, primarily because of electron accumulation at the interface between the quantum dot layer and the hole transport layer.

Innovation Solution

Incorporating a non-emissive quantum dot with a lower LUMO energy level into the quantum dot layer, which acts as a barrier to control electron mobility, thereby balancing hole and electron mobility and preventing electron accumulation, is achieved by using a quantum dot device structure with an emissive quantum dot layer and a non-emissive quantum dot layer, where the non-emissive quantum dot has a LUMO energy level difference of at least 0.5 eV with the electron transport layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional quantum dot layer structure is used, then device structure is simple, but electron accumulation occurs at the interface leading to reduced luminous efficiency and shortened lifespan

Engineering Contradiction:

Improvedevice lifespan and luminous efficiencyVSAvoidquantum dot layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The quantum dot layer is segmented into multiple sub-layers: a first quantum dot layer containing emissive quantum dots, and a second quantum dot layer containing non-emissive quantum dots with higher LUMO energy levels. This segmentation allows different regions to perform different functions - the first layer for light emission and the second layer for electron blocking - thereby resolving the contradiction between maintaining simple structure and improving device reliability by preventing electron accumulation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different quantum dots with specific energy level characteristics are placed in specific locations within the quantum dot layer. The non-emissive quantum dots with higher LUMO energy levels are positioned in the second quantum dot layer adjacent to the hole transport layer, creating a local electron barrier precisely where electron accumulation occurs. This local quality adjustment targets the interface problem without complicating the overall device structure.

Inventive Principle:

Principle #3Local quality

2Productivity

If non-emissive quantum dots are added to balance electron mobility, then luminous efficiency improves, but device structure becomes more complex

Engineering Contradiction:

Improveluminous efficiencyVSAvoidquantum dot layer composition

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The second quantum dot layer containing non-emissive quantum dots serves multiple functions simultaneously: it blocks electron accumulation at the interface with the hole transport layer, maintains charge balance in the device, and preserves the emission characteristics of the first quantum dot layer. This multi-functionality approach improves luminous efficiency without requiring separate components for each function, thereby limiting the increase in device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The quantum dot layer is formed as a composite structure combining emissive quantum dots in the first layer and non-emissive quantum dots in the second layer. Each type of quantum dot contributes specific properties - the emissive ones for light generation and the non-emissive ones for electron transport control. This composite material approach enables improved luminous efficiency through better charge balance while maintaining a relatively integrated and manageable device structure.

Inventive Principle:

Principle #40Composite materials

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 enhances luminous efficiency and extends the lifespan of the quantum dot device by balancing electron and hole mobility, reducing electron accumulation and improving the overall performance.

Implementation Method 1

a difference between an absolute value of a lowest unoccupied molecular orbital (LUMO) energy level of the non-emissive quantum dot and 2. an absolute value of a LUMO energy level of the electron transport layer is greater than or equal to about 0.5 electronvolts (eV)

Methodology Applied

Scientific EffectEnergy level difference (LUMO):

Implementation Method 2

semiconductor nanocrystals also known as quantum dots are supplied with photoenergy or electrical energy and may emit light in a wavelength corresponding to sizes of the quantum dots

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentEP3537491B1Quantum dot device and electronic device

Publication Date: 2022.04.13 SAMSUNG ELECTRONICS CO LTD

Figure 1
Figure 2A~2B
Figure 3

AI summary

A quantum dot device including an anode (11) and a cathode (12) facing each other, a quantum dot layer (14) disposed between the anode and the cathode, and an electron transport layer (13) disposed between the cathode and the quantum dot layer, wherein the quantum dot layer includes an emissive quantum dot (14a) emitting light in at least one part of a wavelength region in a visible region and a non-emissive quantum dot (14b) configured to not emit light in a visible region, and a difference between a lowest unoccupied molecular orbital (LUMO) energy level of the non-emissive quantum dot and a LUMO energy level of the electron transport layer is greater than or equal to about 0.5 electronvolts (eV).