Submicron Gap Thermophotovoltaic Structure
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Solution Overview
Problem
Existing micron/submicron gap thermophotovoltaic devices face challenges in achieving uniform and precise gap dimensions, high fabrication costs, and thermal expansion issues that lead to inefficiencies and structural integrity problems, particularly in large-area systems where heat loss and spacer distortion occur.
Innovation Solution
The integration of a radiation-transparent intermediate window substrate compliantly adhered to the photovoltaic cell, forming a sub-micrometer gap with the heat emitter, using materials like single crystalline semi-insulating GaAs or InP, and a compliant adhesive layer with high refractive index and infrared transmission, which also accommodates surface irregularities and enables up-conversion of photons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick oxide spacers are used to maintain gap between emitter and photovoltaic cell, then mechanical support and gap definition are achieved, but heat loss increases and conversion efficiency decreases
Solution Approach 1:
The patent replaces thick oxide spacers with a thin film vacuum gap structure. The emitter and photovoltaic cell are positioned in vacuum with a gap of less than one micrometer, eliminating the need for thick physical spacers that conduct heat. This thin film approach maintains the necessary mechanical separation while minimizing thermal conduction through the use of vacuum insulation and compliant mounting structures.
Solution Approach 2:
The patent employs vacuum as the medium between emitter and photovoltaic cell. By evacuating the gap to create a vacuum environment, thermal conduction through gas molecules is eliminated, and only radiative heat transfer remains. This pneumatic approach (using vacuum pressure) effectively reduces heat loss while maintaining the operational gap.
2Area of stationary object
If individual emitter chips are brazed to create large-area tiled surfaces, then large area coverage is achieved, but thermal expansion differences cause spacer breakage and geometric distortion
Solution Approach 1:
The patent divides the large-area emitter into an array of smaller emitter chips or elements. Each chip operates independently at high temperature while the photovoltaic cell remains at room temperature. The segmentation allows each unit to expand independently, preventing stress concentration and structural failure that would occur in a monolithic brazed structure.
Solution Approach 2:
The patent introduces compliant mounting structures and flexible support mechanisms that allow the emitter chips to expand and contract dynamically in response to thermal cycling. Rather than rigid brazing that locks the geometry, the dynamic mounting allows for thermal expansion accommodation while maintaining the precise gap distance through elastic deformation of the support structures.
3Productivity
If micrometer-scale gap precision is achieved, then radiative transfer efficiency improves, but fabrication complexity and cost increase
Solution Approach 1:
The patent incorporates gap-defining features directly into the emitter chip fabrication process itself, rather than adding separate spacer components. The emitter substrate is prepared with integrated spacer structures or positioning features during the same manufacturing steps that create the emitter, ensuring precise gap dimensions are built-in from the outset. This preliminary action eliminates subsequent assembly complexity.
Solution Approach 2:
The patent combines multiple functions into the emitter chip structure itself. The emitter substrate serves simultaneously as the heat source, the structural support, and the gap-defining element. By merging the spacer function into the emitter fabrication process rather than using separate components, the system achieves precise sub-micron gap control while simplifying the overall device architecture and reducing assembly steps.
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 configuration allows for a more cost-effective, uniform, and efficient generation of electrical power by maintaining a precise sub-micrometer gap, reducing thermal mismatch, and accommodating non-uniform PV cell surfaces, while enhancing radiative transfer and power generation capabilities.
Implementation Method 1
an infrared-transmitting window in the gap adjacent the photovoltaic cell
Implementation Method 2
enhancing radiative transfer and power generation capabilities
Implementation Method 3
The difference in thermal expansion between the heater and the photovoltaic cell as the heater chip is heated from room temperature to of the order of 1000° C.
Implementation Method 4
a compliant adhesive layer with high refractive index and infrared transmission, which also accommodates surface irregularities
Implementation Method 5
thermophotovoltaic devices (MTPV) for generating electrical power
Data Source
AI summary
An MTPV thermophotovoltaic chip comprising a photovoltaic cell substrate, micron/sub-micron gap-spaced from a juxtaposed heat or infrared radiation-emitting substrate, with a radiation-transparent intermediate window substrate preferably compliantly adhered to the photovoltaic cell substrate and bounding the gap space therewith.