Inverted Metamorphic Multijunction Solar Cell Fabrication
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Solution Overview
Problem
The existing methods for fabricating multijunction solar cells are complex and costly, requiring multiple substrate changes and lengthy temperature ramp-down and ramp-up processes, which hinder high-volume production and increase the cost of producing both standard upright and inverted multijunction solar cells.
Innovation Solution
A method is developed to fabricate both multijunction and inverted metamorphic multijunction solar cells in a single Metal Organic Chemical Vapor Deposition (MOCVD) process, eliminating the need for additional substrates and reducing production time by forming a release layer and growing multiple subcells with varying band gaps and lattice constants on a single semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple substrate changes and temperature ramping processes are used to fabricate both standard and inverted multijunction solar cells, then manufacturing flexibility is improved, but production time and cost increase significantly
Solution Approach 1:
The patent combines the fabrication of both standard upright multijunction solar cells and inverted metamorphic multijunction solar cells into a single continuous MOCVD growth process on one substrate. The method grows a stack containing both cell types sequentially without removing or changing substrates, eliminating multiple substrate changes and temperature ramping cycles. This merging of previously separate fabrication processes into one unified process directly reduces production time while maintaining manufacturing flexibility.
Solution Approach 2:
The patent creates a universal substrate that serves multiple functions: it supports both standard upright multijunction solar cell growth and inverted metamorphic multijunction solar cell growth in sequence. The single substrate performs what previously required multiple specialized substrates, enabling one substrate to fulfill multiple manufacturing roles without compromising the quality or performance of either cell type.
2Manufacturing precision
If multiple substrates are used to fabricate inverted and standard multijunction solar cells separately, then cell quality is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the fabrication of two previously separate processes (standard cell fabrication and inverted cell fabrication on separate substrates) into a single integrated growth process. By growing both cell types in one continuous MOCVD run on one substrate, the method reduces manufacturing complexity while maintaining cell quality through precise control of growth conditions for each cell type within the unified process.
Solution Approach 2:
The patent segments the substrate into distinct regions: a first substrate region for growing the standard upright multijunction solar cell and a second substrate region for growing the inverted metamorphic multijunction solar cell. This spatial segmentation allows each cell type to be fabricated with its specific requirements while both grow simultaneously or sequentially on the same substrate, reducing complexity compared to handling multiple separate substrates.
3Manufacturing precision
If separate fabrication processes are used for standard and inverted multijunction solar cells, then process optimization for each cell type is improved, but overall productivity decreases
Solution Approach 1:
The patent implements continuous useful action by maintaining the MOCVD growth process without interruption. The method grows the standard multijunction solar cell structure, then continues growing the inverted metamorphic multijunction solar cell structure in the same reactor without shutting down, cooling, or changing substrates. This continuous operation maximizes machine throughput and productivity while preserving process optimization for each cell type through controlled growth parameters.
Solution Approach 2:
The patent combines two separate fabrication processes into one unified MOCVD growth run. By merging the production of standard and inverted multijunction solar cells into a single continuous process, the method doubles the effective output per reactor run, significantly improving productivity and machine utilization while maintaining the ability to optimize growth conditions for each cell type.
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 significantly reduces production costs, increases machine throughput, and enables the simultaneous fabrication of two types of solar cells in a single growth run, enhancing efficiency and reproducibility while minimizing physical damage to semiconductor layers.
Implementation Method 1
fabricating both standard upright multijunction solar cells and inverted metamorphic multijunction solar cells in a single MOCVD process
Implementation Method 2
The higher conversion efficiency of III-V compound semiconductor solar cells compared to silicon solar cells is in part based on the ability to achieve spectral splitting of the incident radiation through the use of a plurality of photovoltaic regions with different band gap energies, and accumulating the current from each of the regions
Data Source
AI summary
A method of fabricating both a multijunction solar cell and an inverted metamorphic multijunction solar cell in a single process using a MOCVD reactor by forming a first multijunction solar cell on a semiconductor substrate; forming a release layer over the first solar cell; forming an inverted metamorphic second solar cell over the release layer; and etching the release layer so as to separate the multijunction first solar cell and the inverted metamorphic second solar cell.