Core-Shell Semiconductor Nanocrystals for High Quantum Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor nanocrystals face challenges in achieving high photoluminescence quantum efficiency, with existing materials often resulting in lower emission efficiencies and broader emission spectra.
Innovation Solution
The development of semiconductor nanocrystals with a core comprising a first semiconductor material containing at least three chemical elements and a shell comprising a second semiconductor material, specifically designed to enhance photoluminescence quantum efficiency, where the core and shell materials are carefully selected and structured to achieve high emission efficiencies and narrow emission spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semiconductor nanocrystal materials are used, then the structure is simple, but the photoluminescence quantum efficiency is low
Solution Approach 1:
The patent implements a core-shell nanocrystal structure where a first semiconductor material core is nested within a second semiconductor material shell. This nested configuration allows the inner core to provide specific optical properties while the outer shell enhances photoluminescence quantum efficiency, resolving the contradiction between maintaining structural simplicity and achieving high reliability.
Solution Approach 2:
The patent employs composite semiconductor materials consisting of at least two different semiconductor materials with distinct band gaps. The core contains a semiconductor material with a smaller band gap while the shell contains a material with a larger band gap, creating a type-I band alignment that confines excitons and enhances radiative recombination, thereby improving photoluminescence quantum efficiency without excessive structural complexity.
2Manufacturing precision
If conventional semiconductor nanocrystals are used, then the material composition is simple, but the emission spectrum is broad
Solution Approach 1:
The core-shell nested structure enables precise control over the emission spectrum. The core defines the primary emission characteristics while the shell confines the excitons and narrows the emission line shape. This nested arrangement achieves narrow emission spectra through quantum confinement effects without requiring overly complex multi-layer structures.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different regions of the nanocrystal. The core region provides the fundamental optical transition while the shell region provides exciton confinement and spectral narrowing. This spatial differentiation of functions allows precise control over emission characteristics while maintaining overall structural simplicity.
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 semiconductor nanocrystals exhibit improved photoluminescence quantum efficiency, with efficiencies greater than 65% and often reaching up to 100%, accompanied by a significant reduction in the full width at half maximum of the emission spectrum, indicating a more focused and efficient light emission.
Implementation Method 1
Photoluminescence quantum efficiency (also referred to herein as quantum yield or solution quantum yield) represents the percent of absorbed photons that are reemitted as photons.
Data Source
AI summary
A semiconductor nanocrystal including a core comprising a first semiconductor material comprising at least three chemical elements and a shell disposed over at least a portion of the core, the shell comprising a second semiconductor material, wherein the semiconductor nanocrystal is capable of emitting light with an improved photoluminescence quantum efficiency. Also disclosed are populations of semiconductor nanocrystals, compositions and devices including a semiconductor nanocrystal capable of emitting light with an improved photoluminescence quantum efficiency. In one embodiment, a semiconductor nanocrystal includes a core comprising a first semiconductor material comprising at least three chemical elements and a shell disposed over at least a portion of the core, the shell comprising a second semiconductor material, wherein the semiconductor nanocrystal is capable of emitting light upon excitation with a photoluminescence quantum efficiency greater than about 65%. In another embodiment, a semiconductor nanocrystal includes a core comprising a first semiconductor material comprising zinc, cadmium, and sulfur and a shell disposed over at least a portion of the core, the shell comprising a second semiconductor material. In a further embodiment, a semiconductor nanocrystal includes a core comprises a first semiconductor material comprising at least three chemical elements and a shell disposed over at least a portion of the core, the shell comprising a second semiconductor material comprising at least three chemical elements, wherein the semiconductor nanocrystal is capable of emitting light with a photoluminescence quantum efficiency greater than about 60% upon excitation. In a further embodiment, a semiconductor nanocrystal including a core comprises a first semiconductor material comprising zinc, cadmium, and selenium and a shell disposed over at least a portion of the core, the shell comprising a second semiconductor material, wherein the semiconductor nanocrystal is capable of emitting light with a photoluminescence quantum efficiency greater than about 60% upon excitation.