Tandem Solar Cell Recombination Layer With Thin Metal Stacks
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Solution Overview
Problem
Current tandem solar cells have a significant gap between actual and theoretical photoelectric conversion efficiency, and their structure needs optimization to improve efficiency.
Innovation Solution
A solar cell structure is proposed, comprising a bottom cell, a recombination layer with alternating transparent conductive layers and metal layers, and a top cell. The recombination layer enhances conductivity while reducing thickness and parasitic light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transparent conductive layer is used in the recombination layer, then the layer can maintain transparency, but the electrical conductivity is insufficient leading to high resistance losses
Solution Approach 1:
The patent employs a composite recombination layer structure consisting of alternating transparent conductive layers and metal layers. The transparent conductive layers (e.g., ITO, ZnO) provide transparency and baseline conductivity, while the metal layers (e.g., Ag, Al, Cu) contribute high electrical conductivity. This composite structure achieves superior overall conductivity while maintaining optical transparency, thereby reducing resistance losses in the tandem solar cell recombination layer.
2Reliability
If the recombination layer thickness is increased to improve carrier recombination, then more carriers can be recombined, but light absorption losses increase
Solution Approach 1:
The recombination layer is segmented into multiple thin alternating layers of transparent conductive material and metal material. This segmentation allows the total thickness to be distributed across multiple interfaces, enhancing carrier recombination at each interface while keeping the overall light absorption path limited. The thin-layered structure provides sufficient recombination sites without creating excessive optical absorption losses that would occur in a single thick layer.
Solution Approach 2:
Different regions of the recombination layer are assigned different material properties: transparent conductive layers provide optical transparency and baseline conductivity, while metal layers provide high conductivity and serve as recombination sites. This local differentiation of material quality allows the structure to optimize both carrier recombination (at metal layer interfaces) and light transmission (through transparent conductive layers) simultaneously, minimizing energy losses.
3Reliability
If metal layers are added to improve conductivity, then electrical performance improves, but light transmittance decreases
Solution Approach 1:
The metal layers in the recombination structure are implemented as extremely thin films rather than bulk material. These thin metal films provide sufficient electrical conductivity enhancement while minimizing their optical absorption and reflection. The thin-film approach allows the metal layers to contribute to conductivity without significantly compromising the overall light transmittance of the recombination layer, maintaining the transparency needed for the tandem solar cell operation.
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 improves the carrier recombination efficiency and photoelectric conversion efficiency of the solar cell by reducing resistance and light absorption losses.
Implementation Method 1
The recombination layer is disposed between the second semiconductor conductive layer and the top cell and includes at least two transparent conductive layers and at least one metal layer that are alternatingly stacked in the first direction
Implementation Method 2
a top layer and a bottom layer of the recombination layer are both transparent conductive layers, a respective transparent conductive layer has a first surface in contact with and at least partially covered by a respective metal layer
Data Source
AI summary
Embodiments of the disclosure relate to a solar cell and a photovoltaic module, where the solar cell includes a bottom cell, a recombination layer, and a top cell which are stacked in sequence in a first direction. The bottom cell includes a first semiconductor conductive layer, a substrate, and a second semiconductor conductive layer that are stacked in sequence in the first direction, and the second semiconductor conductive layer is disposed between the substrate and the top cell. The recombination layer is disposed between the second semiconductor conductive layer and the top cell and includes transparent conductive layers and at least one metal layer that are alternatingly stacked in the first direction, a top layer and a bottom layer of the recombination layer are both transparent conductive layers.