TOPCon Solar Cell Rear Microstructures for Better Passivated Contact
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Solution Overview
Problem
The existing manufacturing process for N-type tunnel oxide passivated contact (TOPCon) solar cells faces challenges in removing borosilicate glass, which affects the rear surface structure and subsequently impacts the passivation performance and conversion efficiency of the solar cells.
Innovation Solution
The proposed solution involves creating a solar cell with non-pyramid-shaped microstructures on the rear surface, which includes multiple substructures stacked partially on each other, to improve the open-circuit voltage, reduce contact resistance, and enhance conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If borosilicate glass is formed by boron diffusion on the rear surface, then passivation performance is improved, but the glass is more difficult to remove leading to increased contact resistivity
Solution Approach 1:
The patent introduces an intermediary substance (sulfuric acid-based etching solution with specific composition ratios and additives) to facilitate the removal of borosilicate glass. This intermediary agent enables selective etching of the glass layer without damaging the underlying silicon substrate, thereby resolving the contradiction between maintaining passivation performance and enabling easy glass removal.
Solution Approach 2:
The patent modifies the chemical parameters of the etching solution by controlling the ratio of sulfuric acid to other components, temperature, and exposure time. These parameter changes optimize the etching process to selectively remove borosilicate glass while preserving the silicon substrate, thus reducing contact resistivity without compromising passivation performance.
2Ease of manufacture
If the rear surface is polished with acid additive to achieve flat structure, then manufacturing of tunnel oxide layer is facilitated, but the structure directly affects passivation performance and conversion efficiency
Solution Approach 1:
The patent applies local quality by creating a selectively etched rear surface where the etching is concentrated in specific regions to form a controlled texture pattern. This local modification facilitates tunnel oxide layer formation in contact regions while maintaining smooth passivation regions, thus balancing ease of manufacture with passivation performance.
Solution Approach 2:
The patent introduces a textured surface structure with curved or rounded features rather than a completely flat surface. This curvature facilitates the formation of tunnel oxide layers by providing better contact area while the controlled nature of the texture prevents negative impacts on passivation performance through subsequent selective passivation processes.
3Ease of manufacture
If conventional PERC solar cell structure is used, then manufacturing is easier, but contact resistivity is higher and fill factor fluctuates
Solution Approach 1:
The patent segments the rear surface into distinct functional regions: etched regions for electrical contact and unetched or differently etched regions for passivation. This segmentation allows separate optimization of contact resistivity and fill factor in different areas, improving overall device performance while maintaining manufacturing feasibility through standardized processing steps.
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 improves the uniformity of the tunnel oxide layer, reduces contact resistivity, and increases the open-circuit voltage and fill factor of the solar cells, ultimately leading to higher photoelectric conversion efficiency.
Implementation Method 1
An N-type tunnel oxide passivated contact (TOPCon) solar cell relies on a 'tunnel effect' to achieve passivated contact on a rear surface of the solar cell
Data Source
AI summary
A solar cell includes a semiconductor substrate, in which a rear surface of the semiconductor substrate having non-pyramid-shaped microstructures, the non-pyramid-shaped microstructures include two or more first substructures at least partially stacked on one another, and a one-dimensional size of the surface of the outermost first substructure is less than or equal to 45 μm; a first passivation layer located on a front surface of the semiconductor substrate; first and second tunnel oxide layers located on the non-pyramid-shaped microstructures; first and second doped conductive layers located on a surface of the first and second tunnel oxide layers, the first and second doped conductive layer has different conductive types; a second passivation layer located on a surface of the first and second doped conductive layers; and electrodes formed by penetrating through the second passivation layer to be in contact with the first and second doped conductive layers.