Four-Junction Metamorphic Solar Cell Band Gap Tuning for Space EOL Efficiency
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Solution Overview
Problem
Existing multijunction solar cells for space applications face challenges in maintaining high energy conversion efficiency over the operational life, especially under high temperature and radiation exposure conditions.
Innovation Solution
The design features a lattice mis-matched four-junction solar cell with specific subcell compositions and band gaps optimized for high temperature performance in space, focusing on maximizing efficiency at the end-of-life period rather than the beginning-of-life period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lattice-matched multijunction solar cell designs are used, then high energy conversion efficiency is achieved at beginning-of-life, but efficiency degrades significantly under high temperature and radiation exposure over operational life
Solution Approach 1:
The patent applies preliminary action by pre-compensating for future radiation-induced degradation through intentional lattice mismatch in the solar cell design. The bottom subcell is designed with a band gap that anticipates the degradation of lattice-matched designs, so that after radiation exposure, the metamorphic design maintains higher efficiency than the original lattice-matched configuration.
Solution Approach 2:
The patent changes the critical parameter of lattice matching by intentionally introducing lattice mismatch between the bottom subcell and the upper subcells. This parameter change allows the bottom subcell to have different degradation characteristics under radiation, resulting in improved overall cell efficiency at end-of-life compared to traditional lattice-matched designs.
2Duration of action of moving object
If solar cell efficiency is optimized for beginning-of-life performance, then maximum initial power output is achieved, but performance maintenance over long duration in space environment deteriorates
Solution Approach 1:
The design performs preliminary action by pre-compensating for future radiation damage through intentional lattice mismatch. The bottom subcell is designed with a band gap that anticipates the degradation of traditional lattice-matched designs, ensuring that after radiation exposure, the metamorphic design maintains higher efficiency.
Solution Approach 2:
The patent applies beforehand cushioning by designing the bottom subcell with lattice mismatch to create a buffer against future radiation-induced degradation. This preliminary structural adjustment cushions the overall cell performance from the harmful effects of radiation exposure over the operational lifetime.
3Ease of manufacture
If lattice-matched subcell structure is used, then manufacturing simplicity is maintained, but resistance to radiation damage and high temperature performance worsen
Solution Approach 1:
The patent changes the lattice matching parameter by intentionally introducing mismatch between the bottom subcell and upper subcells. This parameter change fundamentally alters the degradation characteristics under radiation and temperature, improving resistance to harmful space environment factors while maintaining manufacturability through established metamorphic growth techniques.
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 results in improved solar cell efficiency at high temperatures and after exposure to space radiation, maintaining performance over a longer operational life compared to traditional designs.
Implementation Method 1
Solar power from photovoltaic cells, also called solar cells, has been predominantly provided by silicon semiconductor technology
Data Source
AI summary
A method of fabricating four junction solar cell wherein the selection of the composition of the subcells and their band gaps maximizes the efficiency at high temperature (in the range of 50 to 100 degrees Centigrade) in deployment in space at a specific predetermined time after initial deployment (referred to as the beginning of life or BOL), such predetermined time being referred to as the end-of-life (EOL), and being at least five years after the BOL, such selection being designed not to maximize the efficiency at BOL but to increase the solar cell efficiency at the EOL while disregarding the solar cell efficiency achieved at the BOL, such that the solar cell efficiency designed at the BOL is less than the solar cell efficiency at the BOL that would be achieved if the selection were designed to maximize the solar cell efficiency at the BOL.