Heterojunction Cell Segmentation for Resistance Reduction
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Solution Overview
Problem
Heterojunction solar cells face efficiency issues due to high resistivity in transparent conductive films, which are also damaged during high-temperature processing, affecting the cell-to-module ratio and increasing processing costs.
Innovation Solution
A heterojunction cell design featuring interleaved P-type and N-type amorphous silicon layers with transparent conductive layers, connected in series, and additional intrinsic amorphous silicon passivation layers to enhance open-circuit voltage and reduce short-circuit current, allowing for easier encapsulation and packaging with fewer connection points, thus minimizing resistance and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent conductive film is used to cover the heterojunction cell, then the cell structure is completed, but the film has high resistivity which affects energy conversion efficiency
Solution Approach 1:
The transparent conductive film is divided into multiple separate transparent conductive layers that are spaced apart from each other. Each layer connects adjacent amorphous silicon layers of opposite types (P-type and N-type), forming multiple series-connected cell segments. This segmentation reduces the total resistivity by distributing the conductive function across multiple parallel pathways while maintaining structural integrity.
2Ease of manufacture
If high temperature processing is used to fabricate the heterojunction cell, then the amorphous silicon layers are formed, but the transparent conductive film is damaged
Solution Approach 1:
The transparent conductive film is segmented into multiple spaced-apart layers, which reduces the overall material present and distributes thermal stress during high-temperature processing. This segmentation allows the structure to better withstand the thermal loads of amorphous silicon layer formation without causing film damage or delamination.
Solution Approach 2:
The spaced-apart transparent conductive layers act as intermediaries that allow thermal expansion and stress relief during high-temperature processing. The gaps between layers provide buffer zones that prevent continuous film damage while still maintaining electrical connectivity through the conductive pathways.
3Productivity
If the transparent conductive film is damaged during cutting, then the cell can be divided into modules, but the damaged film increases processing cost and reduces CTM ratio
Solution Approach 1:
The transparent conductive film is pre-segmented into multiple spaced layers, which naturally creates separation zones that facilitate clean cutting and module division. These pre-existing gaps reduce the risk of film damage during the cutting process and enable easier integration into modules without requiring additional protective measures or incurring higher processing costs.
4Reliability
If multiple connection points are used in photovoltaic modules, then electrical connectivity is achieved, but resistance increases and power loss occurs
Solution Approach 1:
The cell is divided into multiple series-connected segments through the spaced transparent conductive layers, where each segment connects adjacent P-type and N-type amorphous silicon layers. This segmentation creates fewer required connection points per module while maintaining electrical connectivity, thereby reducing total resistance and minimizing power loss in the photovoltaic module assembly.
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 increases energy conversion efficiency and simplifies the fabrication process by reducing the need for cutting and minimizing damage to transparent conductive layers, leading to higher energy conversion efficiency and lower resistance in photovoltaic modules.
Implementation Method 1
Heterojunction solar cell, as one of the most potential next-generation silicon-based cells, has a high theoretical energy conversion efficiency
Implementation Method 2
a first intrinsic amorphous silicon passivation layer, a first amorphous silicon layer and a plurality of first transparent conductive layers deposited on a first surface of the N-type single crystal silicon layer
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
Provided are a heterojunction cell (100) and a fabrication method thereof. The heterojunction cell (100) includes: a N-type single crystal silicon layer (1); a first intrinsic amorphous silicon passivation layer (2), a first P-type amorphous silicon layer (41) and a first N-type amorphous silicon layer (7) and a first transparent conductive layer (9); and a second intrinsic amorphous silicon passivation layer (3), a second P-type amorphous silicon layer (42), a second N-type amorphous silicon layer (8) and a second transparent conductive layer (10). The first transparent conductive layer (9) is configured to electrically connect the first P-type amorphous silicon layers (41) to the first N-type amorphous silicon layer (7). The second transparent conductive layer (10) is configured to electrically connect the second N-type amorphous silicon layers (8) to the second P-type amorphous silicon layer (42).