Multijunction Solar Cell With Graded Band Gap for Radiation Resistance
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Solution Overview
Problem
Existing multijunction solar cells for space applications face challenges in optimizing energy conversion efficiency, radiation resistance, and manufacturing complexity due to interdependent and unpredictable material design parameters, such as band gaps, lattice matching, and radiation exposure, which affect power output and longevity.
Innovation Solution
Implementing a graded band gap in the active layer of at least one subcell to enhance current collection and radiation performance, while maintaining a constant lattice constant, thereby optimizing the solar cell for different radiation environments and improving efficiency and power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a graded band gap is implemented in the active layer of at least one subcell, then current collection and radiation resistance are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by implementing a graded band gap structure in the active layer of at least one subcell. The band gap energy is varied continuously or in steps through the thickness of the active layer, transitioning from a first band gap energy at the first interface to a second band gap energy at the second interface. This parameter variation enhances radiation resistance and current collection while maintaining lattice matching between subcells.
2Use of energy by moving object
If multiple photovoltaic regions with different band gap energies are used for spectral splitting, then energy conversion efficiency increases, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the solar cell into multiple photovoltaic regions or subcells, each with different band gap energies optimized for specific portions of the solar spectrum. The cell includes a first subcell with a first band gap energy and a second subcell with a second band gap energy, allowing spectral splitting and accumulation of current from each region to achieve high energy conversion efficiency.
Solution Approach 2:
The patent implements parameter changes by varying the band gap energy across different subcells and within the active layer thickness. Each subcell is designed with specific band gap parameters to optimize absorption of different wavelengths, enabling efficient spectral utilization while maintaining manageable device complexity through systematic parameter variation.
3Reliability
If III-V compound semiconductor materials are used instead of silicon, then energy conversion efficiency and radiation resistance improve, but manufacturing complexity increases
Solution Approach 1:
The patent applies composite materials by utilizing III-V compound semiconductor materials (such as gallium arsenide, indium phosphide, or indium gallium arsenide) in the subcells instead of conventional silicon. These compound semiconductors are selected for their superior radiation resistance and ability to achieve higher energy conversion efficiencies through optimized band gap energies, despite increased manufacturing complexity.
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 graded band gap design enhances current collection and radiation resistance, leading to increased photoconversion efficiency and power output, particularly in space environments, by optimizing the solar cell's performance over its operational life.
Implementation Method 1
Solar power from photovoltaic cells, also called solar cells
Implementation Method 2
III-V compound semiconductor multijunction devices have greater energy conversion efficiencies and generally more radiation resistance
Data Source
AI summary
A multijunction solar cell including an upper first solar subcell having an emitter and base layers forming a photoelectric junction; a second solar subcell disposed under and adjacent to the upper first solar subcell, and having an emitter and base layers forming a photoelectric junction; and a third solar subcell disposed under and adjacent to the second solar subcell and having an emitter and base layers forming a photoelectric junction; wherein at least one of the base and emitter layers of at least a particular solar subcell from among the upper first solar subcell, the second solar subcell, and the third solar subcell has a graded band gap throughout at least a portion of thickness of its active layer adjacent to the photoelectric junction and being in a range of 20 to 300 MeV greater than a band gap in the active layer in both the emitter layer and the base layer spaced away from the photoelectric junction.