Tandem Solar Cell Heterojunction Back Structure for Lower Recombination
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Solution Overview
Problem
Existing tandem solar cells face limitations in photoelectric conversion efficiency due to recombination losses between the bottom and top cells, as well as performance losses in the bottom cell, which are exacerbated by the removal of bottom cell structures during manufacturing.
Innovation Solution
The proposed solar cell structure includes a thin-film solar cell stacked with a bottom cell, where the bottom cell features a transparent conductive layer, doped conductive layers, an intrinsic amorphous silicon layer, and a substrate, connected using a heterojunction back structure, which maintains a complete back structure for the bottom cell, reducing contact recombination and eliminating the need for additional intermediate layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bottom cell structure is removed during manufacturing to create tandem solar cells, then the photoelectric conversion efficiency is improved, but the contact recombination loss increases and manufacturing complexity increases
Solution Approach 1:
The patent introduces a transparent conductive layer as an intermediary between the bottom cell and top cell. This layer serves as a mediator that enables electrical connection while minimizing contact recombination losses, resolving the contradiction between improving photoelectric conversion efficiency and reducing contact recombination loss.
Solution Approach 2:
The patent segments the solar cell into distinct functional layers (bottom cell, transparent conductive layer, top cell) with clearly defined interfaces. This segmentation allows each layer to be optimized independently while maintaining overall system efficiency, addressing both the efficiency improvement and harm reduction goals.
2Object-generated harmful factors
If additional intermediate layers are added to connect bottom cell and top cell, then contact recombination is reduced, but device thickness and manufacturing cost increase
Solution Approach 1:
The transparent conductive layer performs multiple functions simultaneously: it serves as an electrical connection medium, a structural support layer, and a optical transmission medium. This multi-functionality reduces the need for additional specialized intermediate layers, thereby controlling device thickness and manufacturing complexity while still reducing contact recombination losses.
3Ease of manufacture
If the bottom cell back structure is incomplete, then manufacturing is simplified, but open-circuit voltage and photoelectric conversion efficiency decrease
Solution Approach 1:
The patent incorporates the complete back structure (including doped conductive layers and intrinsic amorphous silicon layer) into the bottom cell during the initial manufacturing process. This preliminary action ensures that the open-circuit voltage is optimized from the outset, while the modular design maintains manufacturing simplicity by integrating these structures systematically.
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 enhances the open-circuit voltage of the bottom cell, reduces contact recombination between the thin-film and bottom cells, and minimizes the overall thickness and cost of the tandem solar cell, thereby improving the photoelectric conversion efficiency.
Implementation Method 1
Due to the good photoelectric conversion efficiency of solar cells, solar cells have become the focus of development for clean energy utilization
Implementation Method 2
The first doped conductive layer includes a doped amorphous silicon layer or a doped microcrystalline silicon layer
Implementation Method 3
a surface of the substrate facing towards the intrinsic amorphous silicon layer has a plurality of textured structures
Implementation Method 4
the one or more electrodes are formed on a side of the second doped conductive layer away from the substrate and are in ohmic contact with the second doped conductive layer
Data Source
Figure 1~2
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Figure 5~6
AI summary
Embodiments of the present disclosure relate to a solar cell and a photovoltaic module. The solar cell includes a thin-film solar cell and a bottom cell stacked in a first direction. The bottom cell includes: a transparent conductive layer, a first doped conductive layer, an intrinsic amorphous silicon layer, a substrate, a second doped conductive layer, and one or more electrodes that are stacked in the first direction. The transparent conductive layer is between the thin-film solar cell and the first doped conductive layer, and the one or more electrodes are formed on a side of the second doped conductive layer away from the substrate and are in ohmic contact with the second doped conductive layer. The first doped conductive layer includes a doped amorphous silicon layer or a doped microcrystalline silicon layer. The solar cell is at least conducive to reduction of the collection loss of carriers of the solar cell and improvement of photoelectric conversion efficiency of the solar cell.