LED with Composite Dopants and Rotating Substrate Deposition

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Solution Overview

Problem

The use of short-wavelength light-emitting materials as dopants in OLED devices leads to deterioration of viewing angle properties, color change properties, and sharp changes in luminance, while also increasing the size of deposition apparatuses and resulting in waste of organic thin film substances due to non-uniform deposition methods.

Innovation Solution

A light-emitting diode structure with a reflective metal layer and a transparent conductive material layer, incorporating a host and two dopants with specific wavelength relationships between their photo luminescence (PL) and electroluminescence (EL) spectrums, and a deposition apparatus with angled furnaces to ensure uniform deposition of materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If short-wavelength light-emitting materials are used as dopants to improve luminous efficiency, then luminous efficiency is improved, but viewing angle properties deteriorate

Engineering Contradiction:

Improveluminous efficiencyVSAvoidviewing angle properties

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent uses a composite light-emitting layer containing both short-wavelength dopant (for high luminous efficiency) and long-wavelength dopant (for good viewing angle properties). This composite material approach allows combining the advantages of both dopant types, achieving high efficiency while maintaining reliable viewing angle characteristics.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If short-wavelength light-emitting materials are used as dopants to improve luminous efficiency, then luminous efficiency is improved, but color change properties deteriorate

Engineering Contradiction:

Improveluminous efficiencyVSAvoidcolor change properties

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The composite light-emitting layer with both short-wavelength and long-wavelength dopants stabilizes the color output. The long-wavelength dopant compensates for the color instability caused by the short-wavelength dopant, maintaining consistent color properties across different viewing angles while preserving high luminous efficiency.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If conventional deposition methods are used, then deposition process is simple, but uniformity of organic material layer deteriorates

Engineering Contradiction:

Improvedeposition process simplicityVSAvoiduniformity of organic material layer

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent employs a rotating substrate stage during the deposition process. This dynamic approach ensures uniform distribution of organic materials across the substrate surface, achieving consistent layer uniformity while maintaining the simplicity of the deposition process through automated rotation rather than complex manual positioning.

Inventive Principle:

Principle #15Dynamics

4Ease of manufacture

If conventional deposition methods are used, then deposition process is simple, but waste of organic thin film substances increases

Engineering Contradiction:

Improvedeposition process simplicityVSAvoidwaste of organic thin film substances

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The rotating substrate stage optimizes material utilization by ensuring uniform deposition across the entire substrate surface. This prevents material waste through non-uniform distribution, adhesion issues, or redeposition, thereby reducing organic thin film substance loss while keeping the deposition process simple and automated.

Inventive Principle:

Principle #15Dynamics

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 solution enhances luminous efficiency, maintains excellent viewing angle performance, and reduces waste by achieving uniform deposition and improved luminance stability across different viewing angles.

Implementation Method 1

charges are injected into a light-emitting layer formed between a cathode electrode which is an electron injection electrode, and an anode electrode which is a hole injection electrode to form electron-hole pairs, and light is emitted when the electron-hole pairs disappear

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

The organic light-emitting layer is formed by a thermal deposition method of heating a source material in a chamber, and depositing the source material on a target

Methodology Applied

Scientific EffectThermal evaporation: Evaporation

Data Source

PatentUS9150954B2Light-emitting diode and deposition apparatus for fabricating the same

Publication Date: 2015.10.06 LG DISPLAY CO LTD

AI summary

There is provided a light-emitting diode including: a first electrode including a reflective metal layer and a transparent conductive material layer formed on the reflective metal layer; an emitting material layer formed on the first electrode and including a light-emitting layer formed with a host and first and second dopants; and a second electrode formed on the emitting material layer and being a semi-transparent electrode, wherein a first wavelength corresponding to a peak value of a photo luminescence (PL) spectrum of the first dopant is shorter than a second wavelength corresponding to a peak value of an electro luminescence (EL) spectrum of the first dopant, and a third wavelength corresponding to a peak value of a PL spectrum of the second dopant is longer than a fourth wavelength corresponding to a peak value of an EL spectrum of the second dopant.