Alloyed Core-Shell Quantum Dots for High PLQY

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Solution Overview

Problem

Conventional quantum dots for light emitting diodes (LEDs) suffer from low photoluminescence quantum yield (PLQY) due to structural deficiencies such as overlapping absorption and emission profiles, poor nanocrystal surface quality, and self-absorption, which limits their effectiveness in solid-state lighting applications.

Innovation Solution

The development of alloyed nanocrystalline quantum dots with a core-shell structure, where a nanocrystalline core is surrounded by a shell of different semiconductor material, optimizing the aspect ratio and interface quality to minimize self-absorption and enhance radiative recombination, thereby achieving high PLQY.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional quantum dot structures are used, then the device complexity is low, but the photoluminescence quantum yield is low due to overlapping absorption and emission profiles

Engineering Contradiction:

Improvephotoluminescence quantum yieldVSAvoidquantum dot structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The quantum dot is divided into a core and a shell with different semiconductor materials. The core is optimized for absorption while the shell is optimized for emission, separating the functions of absorption and emission to eliminate self-absorption and achieve high photoluminescence quantum yield exceeding 90%.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The quantum dot uses a composite structure with a core made of one semiconductor material and a shell made of a different semiconductor material. This composite material approach allows independent optimization of absorption and emission properties, resolving the contradiction between simple structure and high performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the quantum dot structure is optimized to separate absorption and emission functions, then the photoluminescence quantum yield exceeds 90%, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvephotoluminescence quantum yieldVSAvoidcore-shell interface quality

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Different regions of the quantum dot (core and shell) are assigned different material compositions and properties. The core uses material optimized for absorption while the shell uses material optimized for emission, with each region having locally optimized quality to achieve high overall performance while managing manufacturing precision requirements.

Inventive Principle:

Principle #3Local quality

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 results in quantum dots with PLQYs exceeding 90%, providing improved light emission efficiency and stability for LED applications, with separate optimization of absorption and emission profiles to minimize re-absorption.

Implementation Method 1

quantum dots absorb light of a particular first (available or selected) wavelength, usually blue, and then emit light at a second wavelength, usually red or green

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS10106734B2Alloyed rod structure in a nanocrystalline quantum dot

Publication Date: 2018.10.23 OSRAM OPTO SEMICON GMBH & CO OHG

AI summary

A quantum dot includes a nanocrystalline core and an alloyed nanocrystalline shell made of a semiconductor material composition different from the nanocrystalline core. The alloyed nanocrystalline shell is bonded to and completely surrounds the nanocrystalline core.