Method for optical cooling through semiconductor nanoparticle anti-Stokes photoluminescene
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical cooling technologies face inefficiencies in achieving net cooling due to low quantum yields in bulk semiconductors, primarily because of poor crystalline quality and defects, which limit their ability to achieve temperatures below 10 K effectively.
Innovation Solution
The use of quantum dots with high crystalline quality, carefully selected composition, structure, and size to optimize bandgap, absorption, and emission properties, combined with a polymer matrix for enhanced quantum yield and thermal conductivity, and a vacuum-based system to direct anti-Stokes photons away from the cooling surface for efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk semiconductors are used for optical cooling, then the cooling mechanism can be implemented, but the quantum yield is low due to poor crystalline quality and defects
Solution Approach 1:
The patent divides the bulk semiconductor into nanoscale quantum dots (2-50 nm diameter), which segment the material into discrete quantum states. This segmentation eliminates bulk defects and improves crystalline quality, achieving quantum yields exceeding 90% through size-dependent quantum confinement effects.
Solution Approach 2:
The patent changes the size parameter of the semiconductor material from bulk scale to nanoscale (2-50 nm diameter). This parameter change fundamentally alters the electronic structure and optical properties, enabling high quantum yields and efficient anti-Stokes photoluminescence for optical cooling.
2Productivity
If quantum dots are used to improve quantum yield, then cooling efficiency increases, but the system complexity increases due to need for precise size and composition control
Solution Approach 1:
The patent utilizes size-dependent quantum confinement effects where quantum dots of 2-50 nm diameter exhibit tunable bandgaps and optical properties. By controlling size parameter, the system achieves high quantum yields without requiring complex manufacturing processes, as the quantum dots can be synthesized using established colloidal methods.
Solution Approach 2:
The patent employs core-shell quantum dot structures (e.g., CdSe core with ZnS shell) that combine different materials to achieve both high quantum yield and stability. The core-shell composite structure protects the quantum dot core while enhancing optical properties, reducing the need for extremely precise manufacturing tolerances.
3Temperature
If optical cooling is implemented in bulk semiconductors, then cooling can occur, but temperatures below 10 K cannot be effectively achieved due to phonon mobility drop off
Solution Approach 1:
The patent segments the bulk semiconductor into nanoscale quantum dots, which fundamentally changes the phonon transport properties. The nanoscale dimensions and quantum confinement effects in quantum dots suppress phonon mobility and reduce phonon-mediated energy loss, enabling effective cooling to temperatures below 10 K where bulk semiconductors fail.
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
This approach achieves a material-level coefficient of cooling performance (COPcool) of 0.12 at room temperature, with potential for higher efficiency at lower temperatures, overcoming the limitations of traditional optical coolers by maximizing quantum yield and reducing parasitic heat losses.
Implementation Method 1
exciting the valence band electrons of the quantum dots with a laser and emitting higher energy photons through anti-Stokes up-conversion
Implementation Method 2
the surface of a solid absorbs photons from the laser
Implementation Method 3
emits photons with a higher energy by coupling them with phonons (lattice vibrations)
Data Source
AI summary
A process is disclosed for cooling a material that includes semiconductor nanoparticles in matrix material by anti-Stokes up-conversion. The semiconductor nanoparticle matrix is irradiated by a laser with a photonic wavelength matched to the anti-Stokes photoluminescence of the semiconductor nanoparticle bandgap. The semiconductor nanoparticles absorb the laser photon and phonons (heat) from lattice vibrations to photoluminescence photons with higher energy than the photon that were absorbed. A net cooling effect is generated from the lower energy and lower temperature in the material after anti-Stoke up-conversion.