Monolithic Multi-Junction Solar Cell with Metamorphic Buffer
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Solution Overview
Problem
The production of multi-junction solar cells is complex and cost-intensive, particularly in achieving high radiation hardness and maintaining efficiency over the lifespan, especially in aerospace applications where high radiation doses are involved.
Innovation Solution
A monolithic multi-junction solar cell design comprising a stack of III-V subcells with a metamorphic buffer, where the subcells have n-doped emitter layers and p-doped base layers, with the emitter doping in the second subcell being lower than the base doping, and no direct semiconductor bond between subcells, allowing for reduced degradation under proton irradiation and improved end-of-life efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If direct semiconductor bonding is used to produce multi-junction solar cells, then high efficiency can be achieved, but the production process becomes very complex and cost-intensive
Solution Approach 1:
The patent merges multiple subcells (GaInP, GaAs, Ge) with different band gaps into a single monolithic multi-junction structure, combining their light-absorbing capabilities to achieve high efficiency while avoiding the need for separate bonding processes
2Loss of energy
If conventional multi-junction solar cell designs are used, then initial efficiency can be high, but degradation under proton irradiation is significant
Solution Approach 1:
The patent applies local quality optimization by specifically designing the Ge subcell with tailored doping concentrations and layer structures to be more resistant to proton irradiation, while maintaining the overall multi-junction efficiency
Solution Approach 2:
The patent uses a composite structure combining GaInP, GaAs, and Ge subcells with a metamorphic buffer, where each material contributes its radiation resistance properties, creating a synergistic effect that improves overall reliability under radiation
3Ease of manufacture
If lattice-matched triple-junction solar cells are used, then manufacturing is standardized, but end-of-life efficiency under high radiation doses is insufficient
Solution Approach 1:
The patent changes key parameters including doping concentrations, layer thicknesses, and material composition in the Ge subcell and metamorphic buffer to optimize radiation hardness and maintain high efficiency at end-of-life, while remaining compatible with existing manufacturing capabilities
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
The design significantly reduces efficiency degradation under proton irradiation, enhancing the end-of-life performance and eliminating the need for costly semiconductor bonding, thus improving radiation hardness and manufacturing efficiency.
Implementation Method 1
A metamorphic buffer is formed between the third subcell and the fourth subcell... the lattice constant of the first subcell can differ from the lattice constant of the third subcell by less than 0.3%
Implementation Method 2
at least three or more subcells with different band gaps are stacked on top of one another by means of tunnel diodes
Implementation Method 3
Multi-junction solar cells of this kind are preferably used in space or in terrestrial concentrator photovoltaic systems (CPV)
Data Source
AI summary
A monolithic multi-junction solar cell comprising a first III-V subcell and a second III-V subcell and a third III-V subcell and a fourth Ge subcell, wherein the subcells are stacked on top of one another in the specified order, and the first subcell forms the top subcell and a metamorphic buffer is formed between the third subcell and the fourth subcell and all subcells each have an n-doped emitter layer and a p-doped base layer and the emitter doping in the second subcell is lower than the base doping.