Surface Mount Solar Cells with Integrated Coverglass
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Solution Overview
Problem
Conventional multijunction solar cells for space applications have high assembly costs and reliability issues due to manual welding processes, and they suffer from inefficient surface area utilization and weight penalties, which are exacerbated by the need for bulky interconnects and coverglass application on individual cells.
Innovation Solution
The development of surface mount multijunction photovoltaic cells with through-wafer-vias and all-backside surface mount contacts, integrated coverglass at the wafer-level, allowing for automated assembly using standard electronics industry methods, eliminating the need for welded interconnects and enabling denser packing of cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual welding processes are used to assemble conventional multijunction solar cells, then interconnect reliability can be achieved, but assembly costs increase and productivity decreases
Solution Approach 1:
The patent replaces manual welding processes with automated wire bonding. The wire bonding system uses automated placement and bonding mechanisms to create electrical interconnections between solar cells, eliminating the need for manual welding operations while maintaining reliable electrical connections. This substitution enables automated assembly lines that significantly increase productivity and reduce labor costs.
Solution Approach 2:
The solar cells are designed with self-aligning features including positioning protrusions on the cells that fit into corresponding recesses on the substrate, and the wire bonding process automatically creates connections without requiring manual intervention for alignment or connection formation. The automated bonding system performs both positioning and connection creation in a single automated operation.
2Object-affected harmful factors
If individual coverglass application is performed on each solar cell, then cell protection is achieved, but surface area utilization decreases and weight increases
Solution Approach 1:
The patent combines multiple coverglass units into a single integrated coverglass assembly that spans multiple solar cells. This single coverglass structure provides protection for several cells simultaneously, eliminating the need for individual coverglass application on each cell. The merged design increases surface area utilization by reducing the total coverglass material required and decreases weight by eliminating redundant coverglass structures between adjacent cells.
3Adaptability or versatility
If conventional CIC assembly methods are used, then bypass diode integration is achieved, but device complexity and assembly steps increase
Solution Approach 1:
The patent integrates bypass diodes directly into the substrate structure during the same automated wire bonding process used for interconnect formation. The bypass diodes are placed and bonded in-line with the interconnect operations, combining multiple functions (interconnection and protection) into a single integrated assembly process. This eliminates separate bypass diode installation steps and reduces overall device complexity.
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 assembly costs, increases power density, and decreases the mass of solar arrays by allowing for thinner substrates, while improving reliability and wafer utilization, leading to more efficient and cost-effective solar array production.
Implementation Method 1
The through-wafer-vias are formed using a wet etch process that removes semiconductor materials non-selectively without major differences in etch rates between heteroepitaxial III-V semiconductor layers
Implementation Method 2
Conventional multi-junction solar cells have been widely used for terrestrial and space applications because of their high efficiency
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Photovoltaic cells, methods for fabricating surface mount multijunction photovoltaic cells, methods for assembling solar panels, and solar panels comprising photovoltaic cells are disclosed. The surface mount multijunction photovoltaic cells include through-wafer-vias for interconnecting the front surface epitaxial layer to a contact pad on the back surface. The through-wafer-vias are formed using a wet etch process that removes semiconductor materials non-selectively without major differences in etch rates between heteroepitaxial III-V semiconductor layers.