Multijunction Solar Cell Band Gap Grading for Space Radiation

The patent applies local quality by implementing a graded band gap structure where the band gap energy varies spatially within the active layer of the solar cell. Specifically, the band gap is engineered to increase from the top surface toward the junction, creating different local optical and electrical properties that optimize both current collection and radiation hardness. This non-uniform structure allows different regions of the same layer to serve different functions, resolving the contradiction between simplified design and enhanced performance.

The patent employs parameter changes by systematically varying the band gap energy parameter throughout the active layer thickness. By controlling the composition gradient of the semiconductor material (e.g., varying InGaAsP composition), the band gap is tuned to increase toward the junction. This parameter variation enables optimization of carrier collection efficiency and radiation resistance without requiring fundamentally different device architectures, thus improving reliability while managing complexity.

The patent implements parameter changes by controlling the composition gradient of the semiconductor material during epitaxial growth. The band gap is varied continuously or in steps from the top surface to the junction by adjusting the material composition (e.g., InGaAsP with varying In content). This systematic parameter variation enables optimization of both short circuit current and open circuit voltage while using established manufacturing techniques.

The patent incorporates feedback mechanisms through in-situ monitoring and characterization of the band gap gradient during and after fabrication. By measuring the actual band gap profile and comparing it to the target gradient, manufacturing parameters can be adjusted to achieve the desired power output characteristics. This feedback loop helps manage the precision requirements by enabling real-time or post-process correction of gradient variations.

The patent applies local quality by creating a graded band gap structure within the active layer that provides different local properties optimized for radiation resistance. The gradient in band gap energy creates varying depletion region characteristics and carrier collection efficiencies at different depths, enhancing the cell's ability to withstand radiation damage. This localized property variation achieves improved reliability without requiring multiple separate layers or complex heterostructures.

The patent employs composite materials by using a single semiconductor material system (e.g., InGaAsP) with continuously varying composition rather than discrete layers of different materials. This compositional grading within a unified material system achieves the desired radiation hardness and electrical performance while avoiding the interface defects and manufacturing complexity associated with multi-material heterostructures. The composite approach maintains structural simplicity while achieving enhanced reliability.