Inverted Metamorphic Multi-Junction Solar Cell Fabrication
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Solution Overview
Problem
Inverted metamorphic multi-junction (IMM) solar cells face performance limitations due to lattice and coefficient of thermal expansion (CTE) mismatch between subcells, which can lead to breakage during handling and increased costs from using separate mechanical carriers.
Innovation Solution
The method involves forming subcells on temporary substrates, bonding them to a silicon subcell with metal-to-metal bonds, and removing the temporary substrate to reduce mismatch effects, while the silicon subcell acts as both a functional layer and a carrier to prevent breakage, eliminating the need for additional carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If subcells are formed of materials that are lattice mismatched and/or CTE mismatched to achieve optimal band gaps, then solar energy capture efficiency is improved, but performance is limited due to lattice and CTE mismatch between subcells
Solution Approach 1:
The patent inverts the conventional solar cell fabrication sequence by growing subcells from top to bottom rather than bottom to top. This inversion allows the use of lattice-mismatched materials for optimal band gaps while managing stress accumulation, as each subsequently grown subcell can accommodate the lattice mismatch relative to the underlying layer, thereby resolving the contradiction between achieving optimal energy capture and maintaining structural reliability
2Ease of manufacture
If IMM solar cells are made thin to reduce material usage and cost, then cost effectiveness is improved, but breakage during handling increases
Solution Approach 1:
The patent merges the functional role of the lowermost subcell with the mechanical support function typically provided by a separate carrier. The lowermost subcell is designed to serve dual purposes: as an active photovoltaic element and as a structural support layer that provides mechanical strength to prevent breakage during handling, thereby eliminating the need for additional carrier materials and reducing overall cost while maintaining reliability
3Reliability
If a separate carrier is used to prevent breakage during handling, then handling durability is improved, but cost and device complexity increase
Solution Approach 1:
The patent makes the lowermost subcell universal by assigning it multiple functions: it serves as an active photovoltaic subcell for energy conversion and simultaneously as a mechanical carrier providing structural support and handling durability. This multi-functionality eliminates the need for separate carrier components, reducing device complexity and cost while maintaining improved handling durability
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 reduces the deleterious effects of lattice and CTE mismatch, enhances handling durability, and lowers costs by integrating the silicon subcell as both a performance enhancer and a protective carrier, improving the overall efficiency and cost-effectiveness of IMM solar cells.
Implementation Method 1
solar cells that capture solar energy and convert the solar energy into electrical energy
Implementation Method 2
bonding them to a silicon subcell with metal-to-metal bonds
Data Source
AI summary
An IMM solar cell and an associated method of fabricating an IMM solar cell are provided. In the context of a method, a first subcell may be formed upon a temporary substrate and a second subcell may be formed upon the first subcell. The second subcell may have a smaller band gap than the first subcell. The method may also bond the first and second subcells to a silicon subcell and then remove the temporary substrate. In the context of an IMM solar cell, the IMM solar cell includes first and second subcells with the first subcell disposed upon the second subcell and the second subcell having a smaller band gap than the first subcell. The IMM solar cell may also include a silicon subcell supporting the first and second subcells thereupon with a metal-to-metal bond between the silicon subcell and the second subcell.