White Light Emitter Using Segmented Nanocrystal Shells
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Solution Overview
Problem
Current solid state lighting technologies face challenges in producing white light with high efficiency, stability, and excellent color characteristics, as they struggle to optimize absorption and emission properties of semiconductor nanocrystals, leading to limitations in color adjustment and manufacturing issues.
Innovation Solution
A light-emitting device incorporating low reabsorbing semiconductor nanocrystals with a core, an inner light-absorbing shell, and a protective exterior shell, designed to maximize absorption at the excitation wavelength while minimizing absorption at the emission wavelength, combined with additional light-emitting materials to achieve high photoluminescence quantum yield and tunable emission peak positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional core/shell nanocrystals are used to achieve high photoluminescence quantum yield, then emission efficiency is improved, but absorption at emission wavelengths increases causing reabsorption losses
Solution Approach 1:
The patent segments the nanocrystal into three distinct functional zones: an emission core, an inner light-absorbing shell, and an outer protective shell. This segmentation allows the light-absorbing shell to be optimized for excitation wavelength absorption while the emission core maintains high quantum yield, and the outer shell provides protection without interfering with emission. The spatial separation of absorption and emission functions resolves the contradiction between high quantum yield and low reabsorption loss.
Solution Approach 2:
The patent applies local quality by giving different regions of the nanocrystal different optical properties. The inner shell is specifically engineered to have high absorption coefficient at the excitation wavelength while being transparent at emission wavelengths. This localized optimization of absorption properties in the inner shell region allows the system to achieve both high photoluminescence quantum yield and minimal reabsorption losses.
2Quantity of substance
If the main absorption band is optimized to overlap with emission band for high absorption efficiency, then absorption at excitation wavelength is improved, but reabsorption of emitted light increases
Solution Approach 1:
The patent divides the absorption function between two distinct regions: the inner light-absorbing shell handles excitation wavelength absorption, while the outer protective shell ensures transmission of emission wavelengths. This segmentation of absorption functions at different wavelengths resolves the contradiction by allowing high absorption efficiency at excitation wavelengths without sacrificing emission light.
Solution Approach 2:
The patent inverts the conventional approach by placing the light-absorbing layer inside the emission core rather than outside. This inverted core/shell/shell architecture allows the inner shell to absorb excitation light before it reaches the emission core, preventing reabsorption of emitted light by the outer shell and minimizing energy losses.
3Reliability
If conventional nanocrystal structures are used to achieve stable emission, then emission stability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent segments the protective function into a dedicated outer shell that is optimized solely for protection against photo-oxidation and environmental degradation, while the inner shell handles optical absorption. This segmentation of protective functions simplifies the overall design by assigning specific roles to each layer, making the manufacturing process more controllable and less complex while maintaining high emission stability.
4Reliability
If multiple shell layers are added to protect the emission core, then stability against photo-oxidation is improved, but absorption properties at emission wavelengths worsen
Solution Approach 1:
The patent applies local quality by engineering the outer protective shell with specific optical properties that allow it to provide robust photo-oxidation protection while maintaining high transparency at emission wavelengths. This localized optimization of the outer shell's optical characteristics resolves the contradiction between enhanced stability and maintained emission intensity.
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 enables the production of white light with a high color rendering index, superior lighting performance, and reduced manufacturing costs, offering improved stability and flexibility in lighting applications.
Implementation Method 1
an inner light-absorbing shell... maximize absorption at the excitation wavelength while minimizing absorption at the emission wavelength
Implementation Method 2
emit a second light having an emission maximum in a second wavelength range... high photoluminescence quantum yield
Data Source
AI summary
The present invention relates to a light-emitting device including a light source, a first light-emitting material spaced apart from the light source, and at least one additional light-emitting material. The first light-emitting material includes low reabsorbing semiconductor nanocrystals having an emission-center core, an exterior protective shell, and at least one inner light-absorbing shell. The device is useful for efficiently producing white light having a high color rendering index.