InGaAlAs Grading Interlayer for Multijunction Solar Cell Lattice Mismatch
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Solution Overview
Problem
Current solar cell technologies, particularly inverted metamorphic solar cells, face challenges in achieving commercial viability, manufacturability, and energy efficiency due to lattice mis-matched layers between subcells, which limits their performance in high-demand applications like satellite power systems.
Innovation Solution
A multijunction solar cell structure is developed with a grading interlayer between subcells, optimizing energy efficiency by using a semiconductor body with specific band gaps and lattice mismatched subcells, and a method for manufacturing as a thin, flexible film, involving epitaxial growth and substrate processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If lattice mismatched layers are used between subcells to achieve higher band gap variation, then the energy conversion efficiency is improved, but the manufacturing complexity and defect density increase
Solution Approach 1:
The patent introduces an intermediate grading layer composed of InGaAlAs with gradually varying composition between the InP-based lower subcell and the InGaP-based upper subcell. This grading layer acts as a mediator that progressively transitions the lattice constant and band gap, reducing dislocation density while enabling greater band gap variation for improved energy conversion efficiency across the spectrum
Solution Approach 2:
The patent systematically varies the composition parameters of the InGaAlAs grading layer, controlling the indium, gallium, and aluminum ratios to create a gradual transition in lattice constant and band gap. By adjusting these compositional parameters through the grading layer thickness, the invention achieves optimal balance between reducing lattice mismatch effects and maintaining manufacturability
2Power
If multiple subcells with different band gaps are stacked to capture broader spectrum, then the power and energy conversion characteristics are improved, but the size and mass of the satellite power system increase
Solution Approach 1:
The patent employs a composite multijunction structure combining InP-based lower subcell, InGaAlAs grading layer, and InGaP-based upper subcell. Each material component is selected for its specific band gap properties, creating a composite structure that captures broader solar spectrum with higher conversion efficiency, thereby generating more power per unit mass for satellite applications
3Reliability
If the grading interlayer is made thicker to reduce dislocation density, then the reliability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality control by creating regions of different grading rates within the InGaAlAs layer. The composition gradient is optimized at different depths - with steeper grading near the interfaces and more gradual transitions in the middle section. This localized variation in grading quality allows sufficient thickness for dislocation reduction while maintaining manageable epitaxial growth precision requirements
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 solution enhances energy efficiency and manufacturability of solar cells, addressing the limitations of prior art by maximizing energy conversion and enabling more efficient power generation for sophisticated applications.
Implementation Method 1
Photovoltaic cells, also called solar cells, are one of the most important new energy sources that have become available in the past several years
Implementation Method 2
a method of manufacturing an inverted metamorphic solar cell as a thin, flexible film, involving epitaxial growth and substrate processing steps
Data Source
AI summary
A method of forming a multijunction solar cell that includes an InGaAs buffer layer and an InGaAlAs grading interlayer disposed below, and adjacent to, the InGaAs buffer layer. The grading interlayer achieves a transition in lattice constant from one solar subcell to another adjacent solar subcell.