Five-Junction Metamorphic Solar Cell With Low-Resistance Top Subcells
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Solution Overview
Problem
Multi-junction solar cells with aluminum-containing top cells face efficiency reductions due to increased series resistance and material degradation, particularly in concentrator applications, where high current loads and radiation exposure exacerbate these issues.
Innovation Solution
A stacked, monolithic, upright metamorphic solar cell with five subcells and a metamorphic buffer, where the top subcells have reduced aluminum content and a specific band gap structure, ensuring low sheet resistance and improved material quality, is developed. The metamorphic buffer adjusts lattice constants to enhance transverse conductivity and reduce shading losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If aluminum content is increased in the top subcells to increase the band gap, then the band gap increases, but the material properties deteriorate and solar cell efficiency reduces
Solution Approach 1:
The patent applies parameter changes by precisely controlling the aluminum content in the top subcells to be less than 10% (preferably less than 5% or even less than 1%), rather than using high aluminum content. This parameter optimization allows achieving sufficient band gap for high-efficiency spectrum utilization while avoiding material property deterioration and maintaining good solar cell performance
Solution Approach 2:
The patent uses composite material structures in the top subcells, combining InGaP and InAlGaP materials with optimized composition ratios. This composite approach allows tuning the band gap through compositional control while maintaining material quality and avoiding the degradation issues associated with high-aluminum-content single materials
2Length of moving object
If aluminum is used in the topmost subcell to increase band gap, then the band gap increases, but the mobility of majority charge carriers reduces and sheet resistance increases
Solution Approach 1:
The patent optimizes the aluminum content parameter in the top subcells to be less than 10%, which balances band gap requirements with electrical conductivity. This parameter control ensures sufficient transverse conductivity and low sheet resistance for concentrator applications while achieving the necessary band gap for high efficiency
Solution Approach 2:
The patent applies different aluminum content levels in different subcells, with the top subcells having low aluminum content (less than 10%) to maintain conductivity, while other subcells can have higher aluminum content where conductivity requirements are less stringent. This local optimization resolves the contradiction between band gap and conductivity
3Productivity
If upright metamorphic structure with high aluminum content is used, then the band gap can be increased for higher efficiency, but the minority charge carrier lifetime reduces significantly
Solution Approach 1:
The patent changes the aluminum content parameter in the top subcells to be less than 10%, which maintains good minority charge carrier lifetime in the upright metamorphic structure while still achieving sufficient band gap for high efficiency. This parameter optimization resolves the contradiction between efficiency and carrier lifetime
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 configuration enhances the efficiency of concentrator solar cells by minimizing series resistance and maintaining high transverse conductivity, even at high concentration factors, thereby improving overall performance and durability.
Implementation Method 1
The metamorphic buffer adjusts lattice constants to enhance transverse conductivity and reduce shading losses
Implementation Method 2
multi-junction solar cells generally comprise three or more subcells with different, matched band gaps, wherein the topmost subcell has the largest band gap and the lowest subcell has the lowest band gap
Data Source
AI summary
A stacked, monolithic, upright metamorphic, terrestrial concentrator solar cell having exactly five subcells and having a metamorphic buffer, wherein a first subcell has a first lattice constant G1 and consists essentially of germanium, a second subcell has a second lattice constant and GaInAs, a third subcell has the second lattice constant G2 and AlGaInAs, a fourth subcell has the second lattice constant G2 and InP, a fifth subcell has the second lattice constant G2 and InP, G1<G2 applies to the lattice constants, the metamorphic buffer is arranged between the first subcell and the second subcell and has the first lattice constant G1 on a bottom side facing the first subcell and the second lattice constant G2 on a top side facing the second subcell, and all of the semiconductor layers of the concentrator solar cell arranged above the first subcell are epitaxially produced on the preceding subcell.