Bonded Transparent Conductive Interlayer for Multijunction Solar Cells
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Solution Overview
Problem
Existing multijunction solar cells face limitations in efficiency due to lattice constant mismatches between materials, restricting the choice of substrates and materials that can be used, and bonded solar cells often lack electrical conductivity, optical transparency, or mechanical strength.
Innovation Solution
The use of a Transparent Conductive Coating (TCC) to bond subcells together, allowing for electrical contact while maintaining optical transparency, and optimizing the thickness and composition of the TCC layers to enhance light transmission and reflection between subcells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different solar cell materials are grown monolithically onto a substrate, then the cell can absorb different wavelengths of light efficiently, but the lattice constants of the materials must be closely matched which limits the choice of materials
Solution Approach 1:
The solar cell is divided into multiple separate subcells that are bonded together, rather than grown as a single monolithic structure. This segmentation allows each subcell to be made from different materials with different lattice constants, eliminating the need for lattice matching while maintaining the ability to absorb different wavelengths of light efficiently.
Solution Approach 2:
A bonding layer is introduced as an intermediary between different subcells made from materials with mismatched lattice constants. This bonding layer allows the subcells to be mechanically and electrically connected without requiring direct lattice matching, enabling the use of a wider range of materials for different wavelength absorption.
2Adaptability or versatility
If solar cell materials are bonded together to overcome lattice constant limitations, then a wider range of materials can be used, but the bond must be electrically conductive, optically transparent, and strong enough which has been difficult to achieve
Solution Approach 1:
The bonding layer is designed to perform multiple functions simultaneously: it provides mechanical bonding strength to hold subcells together, electrical conductivity to allow current flow between subcells, and optical transparency to minimize light loss. This multi-functional bonding layer resolves the contradiction by satisfying all three requirements with a single solution.
Solution Approach 2:
The bonding layer uses composite material structures, such as transparent conductive oxides (TCO) like indium tin oxide (ITO) or indium zinc oxide (IZO), which combine the properties of transparency and electrical conductivity. These composite materials enable the bond to meet all three critical requirements: mechanical strength, electrical conductivity, and optical transparency.
3Reliability
If a Transparent Conductive Coating (TCC) is used to bond subcells, then electrical contact and optical transparency are achieved, but the thickness of the TCC must be optimized to balance transmission and reflection
Solution Approach 1:
The thickness of the TCC layer is precisely controlled and optimized as a key parameter. By adjusting the thickness within a specific range, the bonding layer achieves sufficient electrical conductivity for current flow while minimizing optical absorption and reflection losses. This parameter optimization resolves the contradiction between electrical performance and optical efficiency.
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 approach enables the use of a wide range of materials to absorb different wavelengths of light, increases the efficiency of multijunction solar cells, and maintains material bonding, overcoming the limitations of lattice constant mismatches and material constraints.
Implementation Method 1
The TCC provides electrical contact between the two subcells while allowing for optical transmission
Implementation Method 2
The thickness of the TCC may be used in conjunction with other optical coatings to optimize the transmission and reflection between the subcells
Implementation Method 3
The TCC provides electrical contact between the two subcells while allowing for optical transmission
Implementation Method 4
Different materials are used to absorb different wavelengths of light in the spectrum, each material chosen to absorb a specific range of wavelengths such that the cell can be more efficient
Data Source
AI summary
Methods and apparatuses for creating solar cell assemblies with bonded interlayers are disclosed. In summary, the present invention describes an apparatus and method for making a solar cell assembly with transparent conductive bonding interlayers. An apparatus in accordance with the present invention comprises a substrate, a first solar cell, coupled to a first side of the substrate, wherein the first solar cell comprises a first Transparent Conductive Coating (TCC) layer coupled to a first polarity electrode of the first solar cell, and a second solar cell, the second solar cell being bonded to the first solar cell by bonding the first TCC layer to the second solar cell.