Core/Shell Semiconductor Nanocrystals Narrowing Emission Spectra
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Solution Overview
Problem
Current semiconductor nanocrystals face limitations in achieving high photoluminescence quantum efficiency, typically below 50%, and have broad emission spectra with full width at half maximum (FWHM) greater than 20 nm, which hampers their efficiency in light emission applications.
Innovation Solution
Development of semiconductor nanocrystals with core/shell structures, specifically using ZnxCd1-xS as the core and ZnS as the shell, where x ranges from 0 to 1, to enhance photoluminescence quantum efficiency and narrow the emission spectrum, achieving efficiencies greater than 90% and FWHM less than 20 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semiconductor nanocrystals are used, then the structure is simple, but the photoluminescence quantum efficiency is low (below 50%) and the emission spectrum is broad (FWHM greater than 20 nm)
Solution Approach 1:
The patent implements a core/shell nanocrystal structure where a first semiconductor nanocrystal core is nested within a second semiconductor nanocrystal shell. This nested configuration allows the inner core to provide photoluminescence emission while the outer shell protects and enhances the optical properties, achieving photoluminescence quantum efficiency greater than 50% and FWHM less than 20 nm
Solution Approach 2:
The patent uses composite semiconductor materials with different band gaps - a first semiconductor material with a first band gap for the core and a second semiconductor material with a second band gap for the shell. This composite structure enables optimized optical confinement and emission properties, resolving the contradiction between structural simplicity and high photoluminescence performance
2Manufacturing precision
If conventional semiconductor nanocrystals are used, then the manufacturing process is simple, but the emission spectrum width is broad (FWHM greater than 20 nm)
Solution Approach 1:
The patent controls the emission spectrum by precisely adjusting material composition parameters (x in ZnxCd1-xS ranging from 0 to 1) and structural parameters (core radius, shell thickness). By changing these parameters, the emission wavelength and FWHM are tuned to achieve narrow spectra (FWHM less than 20 nm) while maintaining manufacturability through controlled chemical vapor deposition
3Productivity
If high photoluminescence quantum efficiency is achieved through core/shell structure, then light emission efficiency improves, but the device complexity increases
Solution Approach 1:
The patent achieves high light emission efficiency (photoluminescence quantum efficiency greater than 50%, preferably greater than 75%) by implementing a direct optical transition pathway through the core/shell structure that skips non-radiative recombination paths. The type I band alignment enables direct electron-hole recombination in the core, producing high efficiency emission while maintaining a relatively simple two-layer structure
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 core/shell structure significantly improves photoluminescence quantum efficiency to over 90% and narrows the emission spectrum, resulting in more efficient light emission with a peak emission wavelength not exceeding 470 nm, suitable for various light-emitting devices and applications.
Implementation Method 1
Photoluminescence quantum efficiency (also referred to 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 capable of emitting light with an improved photoluminescence quantum efficiency. The present invention further relates to compositions and devices including semiconductor nanocrystals capable of emitting light with an improved photoluminescence quantum efficiency. A semiconductor nanocrystal wherein the semiconductor nanocrystal is capable of emitting light with a photoluminescence quantum efficiency greater than about 50% upon excitation and including a maximum peak emission with a FWHM less than 20 nm is disclosed. Also disclosed are a device, a population of semiconductor nanocrystals, and a composition including a semiconductor nanocrystal wherein the semiconductor nanocrystal is capable of emitting light with a photoluminescence quantum efficiency greater than about 50% upon excitation and including a maximum peak emission with a FWHM less than 20 nm. A semiconductor nanocrystal that is capable of emitting light upon excitation with a photoluminescence quantum efficiency greater than about 90%. Also disclosed are a device, a population, and a composition including a semiconductor nanocrystal.