Multi-Junction Solar Cell Mirror Layout for Higher Photocurrent
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Solution Overview
Problem
Existing stacked monolithic multi-junction solar cells face limitations in efficiency and radiation stability due to conventional doping levels in buffer layers and semiconductor mirror placements, which affect conductivity and photocurrent.
Innovation Solution
A novel configuration is introduced where the tunnel diode is placed between the semiconductor mirror and the subcell, with a low-doped metamorphic buffer and n-doped semiconductor mirror layers, and a metamorphic buffer with step-like lattice constant changes, enhancing the efficiency and photocurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional doping levels are used in buffer layers, then conductivity is maintained, but efficiency and photocurrent are reduced
Solution Approach 1:
The patent changes the doping parameter in buffer layers from conventional levels (typically >10^18 cm^-3) to reduced levels (10^16-10^18 cm^-3), thereby improving efficiency and photocurrent while maintaining acceptable conductivity through optimized layer design and positioning of the semiconductor mirror
2Reliability
If the semiconductor mirror is placed directly below the subcell, then reflection behavior is optimized, but radiation stability and efficiency are reduced
Solution Approach 1:
The patent introduces a vertical dimension adjustment by placing the semiconductor mirror not directly below the subcell but at an optimized distance within the metamorphic buffer layer, creating an intermediate position that simultaneously achieves good reflection behavior and high efficiency through reduced parasitic absorption
3Reliability
If high doping levels are used in buffer layers, then conductivity is improved, but radiation stability and photocurrent are reduced
Solution Approach 1:
The patent optimizes the doping parameter in buffer layers to reduced levels (10^16-10^18 cm^-3), which improves radiation stability and photocurrent by reducing defect formation and carrier recombination, while maintaining sufficient conductivity through the overall device architecture design
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
This configuration significantly improves the efficiency and radiation stability of the multi-junction solar cell by increasing photocurrent and maintaining good reflection behavior.
Implementation Method 1
the semiconductor mirror has a plurality of layers with refractive indices that at least differ from one another and a high degree of reflection in at least one part of the absorption range of the subcell or subcells placed thereabove
Implementation Method 2
If the first and second subcells have different lattice constants, the multi-junction solar cell thus comprises a metamorphic buffer placed between the first and second subcells
Implementation Method 3
A tunnel diode with a p-n junction can be placed between two subcells in each case
Implementation Method 4
a stacked monolithic multi-junction solar cell... comprises a first germanium subcell as well as at least two further subcells
Data Source
AI summary
A stacked monolithic multi-junction solar cell having at least four subcells, wherein the band gap increases starting from the first subcell in the direction of the fourth subcell, each subcell has an n-doped emitter and a p-doped base, the emitter and the base of the first subcell each have germanium or consist of germanium, all following subcells each have at least one element of main group III and V of the periodic table, a tunnel diode with a p-n junction is placed between each two subcells, all subcells following the first subcell are formed lattice-matched to one another, a semiconductor mirror having a plurality of doped semiconductor layers with alternately different refractive indices is placed between the first and second subcell, and the semiconductor mirror is placed between the first subcell and the first tunnel diode.