GaInNAsSb Multijunction Photovoltaic Cells
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Solution Overview
Problem
Current multijunction photovoltaic cells with three junctions face limitations in achieving higher efficiencies due to challenges in finding suitable materials for lattice-matched structures with four or more subcells, leading to increased semiconductor material usage and reliability concerns, particularly with metamorphic materials.
Innovation Solution
The development of multijunction photovoltaic cells with four, five, or more subcells using GaInNAsSb subcells, where the composition is tailored for specific band gaps and lattice constants, ensuring substantial lattice-matching among subcells and to substrates, thereby reducing material usage and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metamorphic materials are used to create four or more subcells, then the number of junctions increases, but reliability deteriorates and material usage increases
Solution Approach 1:
The patent changes the material parameters by using lattice-matched GaInNAsSb alloys with specific compositions (varying In and Sb content) to achieve different band gaps while maintaining lattice matching to the substrate. This allows creating four or more subcells with precise parameter control without the reliability issues of metamorphic materials
Solution Approach 2:
The patent employs composite material structures where multiple GaInNAsSb layers with different compositions are stacked to form subcells. Each layer is carefully engineered with specific In and Sb content to achieve the desired band gap sequence while maintaining lattice matching, creating a composite structure that avoids metamorphic discontinuities
2Productivity
If metamorphic materials are used for additional subcells, then the number of junctions increases, but semiconductor material usage increases
Solution Approach 1:
By changing the compositional parameters of GaInNAsSb alloys, the patent achieves different band gaps in each subcell without requiring thick buffer layers or metamorphic transition layers. This precise parameter control reduces the total semiconductor material volume needed compared to metamorphic approaches
3Ease of manufacture
If conventional materials are used for three junction cells, then manufacturing is simpler, but efficiency improvement is limited
Solution Approach 1:
The patent applies local quality by creating spatial variations in material composition across different subcells. Each subcell has a specific GaInNAsSb composition tailored to absorb a particular portion of the solar spectrum, with In and Sb content optimized for that local function. This allows efficiency enhancement while maintaining a relatively simple monolithic manufacturing process
Solution Approach 2:
The patent systematically changes material parameters (band gap, lattice constant) by adjusting In and Sb composition in GaInNAsSb to create four or more subcells with optimized energy levels. This enables higher efficiency through better spectral utilization while maintaining compatibility with existing manufacturing 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
These cells achieve higher efficiencies by optimizing light absorption and reducing series resistance losses, with GaInNAsSb subcells demonstrating high internal quantum efficiency and radiation hardness, capable of maintaining performance over extended periods and in space environments.
Implementation Method 1
The subcells contain the regions of the photovoltaic cell where light energy in a range of wavelengths is absorbed and converted into electrical energy that may be collected externally
Data Source
AI summary
Multijunction photovoltaic cells having at least three subcells are disclosed, in which at least one of the subcells comprises a base layer formed of GaInNAsSb. The GaInNAsSb subcells exhibit high internal quantum efficiencies over a broad range of irradiance energies.