III-V Multijunction Solar Cell Contacts for Low-Reflection Absorption
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Solution Overview
Problem
Existing III-V multijunction solar cells face efficiency reduction due to high reflection and heating, particularly in the infrared and visible spectral ranges, which is exacerbated by the use of gold layers for finger-shaped metal structures.
Innovation Solution
A stack-type III-V multijunction solar cell design incorporating a substrate layer with a first subcell and a second subcell having a larger bandgap, a tunnel diode, and a silver-based first contact region with an absorbent layer that reduces reflection and increases absorption, accompanied by a titanium or black nickel layer to enhance adhesion and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gold layer is used as the cover layer on finger-shaped metal structures, then electrical conductivity and adhesion are improved, but reflection increases and manufacturing cost increases
Solution Approach 1:
The patent replaces expensive gold layers with a more cost-effective multi-layer structure consisting of aluminum and silver layers. This substitution maintains the necessary electrical conductivity and adhesion functions while significantly reducing manufacturing costs and minimizing energy loss through reflection.
2Reliability
If a gold layer is used as the cover layer on finger-shaped metal structures, then adhesion is improved, but manufacturing cost increases
Solution Approach 1:
The patent substitutes expensive gold materials with affordable aluminum and silver layers in the contact structure. This material replacement maintains adequate adhesion properties for reliable electrical connection while dramatically reducing manufacturing costs, making the solar cell more economically viable.
3Area of stationary object
If the finger-shaped metal structures are minimized to reduce shading, then electrical connection capability is reduced, but surface area for light absorption is increased
Solution Approach 1:
The patent employs a composite multi-layer structure (aluminum and silver layers) in the finger-shaped contact regions. This composite design enables the metal structures to be minimized for reduced shading while maintaining adequate electrical connection capability through the synergistic properties of the combined layers, thereby maximizing the surface area available for light absorption.
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 design enhances efficiency to over 30% photoelectric and 25% thermal efficiency, reduces manufacturing costs, and allows for combined photoelectric and solar thermal applications with improved heat management.
Implementation Method 1
The absorbent layer has an average absorptivity for solar radiation of more than 0.5 and a reflection coefficient of less than 80% in the infrared wavelength range and/or the visible portion of the wavelength range
Implementation Method 2
A tunnel diode can be formed between the first subcell and the second subcell
Implementation Method 3
III-V multijunction solar cells are provided with a stack-type design and have an efficiency of more than 30%
Data Source
AI summary
A stack-type III-V multijunction solar cell having an upper side and an underside, which includes a substrate layer formed on the underside and a first subcell having a first bandgap on the substrate layer or comprising the substrate layer. A second subcell has a second bandgap and is arranged above the first subcell. A tunnel diode is formed between the first subcell and the second subcell. A finger-shaped first metallic contact region is formed on the upper side. A second metallic contact region is formed over a wide area on the underside. The first contact region comprises multiple metal layers and has a first metal layer comprising silver in a vicinity of the surface and has a titanium layer designed as the uppermost metal layer above the first metal layer to reduce reflection on the upper side. The titanium layer has a thickness of more than 5 nm.