Multijunction Solar Cell Structure Without Semiconductor Bonding
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Solution Overview
Problem
The high manufacturing costs and complexity of multi-junction solar cells, particularly due to substrate deposition, removal, and bonding processes, as well as the need for improved radiation hardness and efficiency across the lifespan of space solar cells, are significant challenges in the development of efficient solar cells.
Innovation Solution
A stacked multi-junction solar cell design featuring a predominantly germanium first sub-cell, a GaInAsP second sub-cell with higher radiation stability, and subsequent sub-cells with specific compound layers and metamorphic buffers, all connected without semiconductor bonding, to reduce production costs and enhance radiation hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor bonding technology is used to create multi-junction solar cells, then efficiency is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent extracts and eliminates the semiconductor bonding step from the manufacturing process. Instead of bonding two separate epitaxial wafers together, all subcells are grown in a single continuous epitaxial process on one substrate, removing the need for substrate removal and bonding operations while maintaining multi-junction efficiency
Solution Approach 2:
The patent merges multiple deposition steps and substrate operations into a single epitaxial growth process. All subcells are deposited sequentially on the same substrate without intermediate substrate removal or bonding, combining what were previously separate manufacturing stages into one integrated process
2Manufacturing precision
If multiple separate deposition steps on different substrates are used, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple separate deposition processes into a single continuous epitaxial growth operation. All subcells are grown in sequence on the same substrate without interruption, eliminating the need for multiple substrate loadings, bondings, and alignments while maintaining precise layer control through in-situ composition adjustments
3Reliability
If substrate removal and bonding processes are implemented, then multi-junction efficiency is improved, but manufacturing time increases
Solution Approach 1:
The patent removes the time-consuming substrate removal and bonding steps from the manufacturing sequence. By growing all subcells in a single epitaxial process, the method eliminates weeks of processing time associated with wafer bonding while achieving equivalent or superior multi-junction performance
Solution Approach 2:
The patent performs preliminary design of the complete multi-junction structure in the epitaxial growth plan, pre-determining all layer compositions, thicknesses, and doping profiles before growth begins. This allows all subcells to be manufactured in one continuous process without intermediate steps, significantly reducing total manufacturing time
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 design reduces manufacturing costs, increases radiation stability, and maintains or improves initial efficiency while enhancing end-of-life efficiency by using germanium and GaInAsP compounds, and metamorphic buffers to adjust energy band gaps, resulting in a more efficient and cost-effective solar cell.
Implementation Method 1
the phosphorus content of the layer is greater than 1% and less than 45% and the indium content of the layer is less than 50%, and the lattice constant of the layer is less than 5.84 Å, and the lattice constant of the layer of the third subcell differs from the lattice constant of the layer of the second subcell by less than 0.2%
Implementation Method 2
A metamorphic buffer of Ga Y In 1-Y As is used between the Ge substrate or the Ge subcell and the Ga 0.83 In 0.17 As subcell
Data Source
Figure 1~2d
Figure 3a~3f
AI summary
Stacked multi-junction solar cell having a first sub-cell, the first sub-cell having predominantly germanium, and having a second sub-cell, the second sub-cell having a larger band gap than the first sub-cell, and having a third sub-cell, the third sub-cell having a larger band gap than the second sub-cell has, and each of the sub-cells has an emitter and a base, and wherein the second sub-cell comprises a layer with a compound with at least the elements GaInAsP and the thickness of the layer is greater than 100 nm and the layer as part of the emitter and / or as part of the base and / or as part of the space charge zone located between the emitter and base, the third partial cell has a layer with a compound containing at least the elements GaInP and the thickness of the layer is greater than 100 nm and the layer as a part of the emitter and/or as part of the base and/or as part of between the emitter and Ba sis lying space charge zone is formed, and in the second partial cell the phosphorus content of the layer is greater than 1% and less than 45% and the indium content of the layer is less than 50%, and the lattice constant of the layer is less than 5.84 Å, and the lattice constant of the layer of the third sub-cell differs from the lattice constant of the layer of the second sub-cell by less than 0.2%, and no semiconductor bond is formed between two sub-cells of the multi-junction solar cell.