GaInNAsSb Alloy for Multijunction Solar Cell Current Matching
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Solution Overview
Problem
Current multijunction solar cells with III-V semiconductor alloys face inefficiencies due to the bottom junction generating excessive short circuit current, which is not effectively utilized, and materials like GaInNAsSb struggle to achieve high open circuit voltages and current matching with other subcells.
Innovation Solution
A low-antimony, enhanced indium and nitrogen alloy composition, Ga1-xInxNyAs1-y-zSbz, with specific ranges of 0.07≤x≤0.18, 0.025≤y≤0.04, and 0.001≤z≤0.03, is developed to achieve a bandgap of 0.9-1.1 eV, enabling high short circuit currents and open circuit voltages, suitable for multijunction solar cells, and can be grown using molecular beam epitaxy or metallorganic chemical vapor deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the bottom junction is made of Ge substrate with (In)GaAs material, then the short circuit current capability is enhanced, but the current matching with upper junctions deteriorates due to excessive current generation
Solution Approach 1:
The patent changes the material composition parameters by introducing Ga1-xInxNyAs1-y-zSbz alloy with specific compositional ranges (0.05≤x≤0.07, 0.01≤y≤0.02, 0.02≤z≤0.06) to adjust the bandgap and electrical properties, enabling current matching while maintaining high current capability
Solution Approach 2:
The patent uses composite material GaInNAsSb alloy combining multiple elements (Ga, In, N, As, Sb) with controlled concentrations to achieve simultaneous lattice matching to Ge and GaAs substrates while providing appropriate electrical characteristics for current matching in multijunction configuration
2Productivity
If GaInNAsSb material is used to create a third junction with band gap of approximately 1.0 eV, then the efficiency is improved, but the open circuit voltage remains limited to approximately 0.30 V
Solution Approach 1:
The patent modifies the material parameters by optimizing the compositional ranges of Ga1-xInxNyAs1-y-zSbz alloy, particularly controlling the indium (x), nitrogen (y), and antimony (z) concentrations to achieve improved open circuit voltage while maintaining the bandgap near 1.0 eV for efficiency
3Reliability
If lattice-matched devices are used, then the reliability is improved and semiconductor material usage is reduced, but the design flexibility is limited compared to metamorphic structures
Solution Approach 1:
The patent achieves multi-functionality by developing GaInNAsSb material that simultaneously provides lattice matching to both Ge and GaAs substrates, enabling the same material system to be used in different multijunction configurations (triple junction, four junction, or more) with different substrate choices, thus providing both reliability of lattice-matched devices and design flexibility
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 new alloy composition allows for design-tunable subcells with improved efficiency, achieving higher open circuit voltages and current matching, enhancing the performance of multijunction solar cells, particularly in triple and four-junction configurations, with efficiencies up to 39.2% under concentrated illumination.
Implementation Method 1
Multijunction solar cells made primarily of III-V semiconductor alloys are known to produce solar cell efficiencies exceeding efficiencies of other types of photovoltaic materials
Implementation Method 2
The top subcell has been made of (Al)GaInP, the middle one of (In)GaAs, and the bottom junction included the Ge substrate
Data Source
AI summary
An alloy composition for a subcell of a solar cell is provided that has a bandgap of at least 0.9 eV, namely, Ga1-xInxNyAs1-y-zSbz with a low antimony (Sb) content and with enhanced indium (In) content and enhanced nitrogen (N) content, achieving substantial lattice matching to GaAs and Ge substrates and providing both high short circuit currents and high open circuit voltages in GaInNAsSb subcells for multijunction solar cells. The composition ranges for Ga1-xInxNyAs1-y-zSbz are 0.07≤x≤0.18, 0.025≤y≤0.04 and 0.001≤z≤0.03.