Bifacial Punched PERC Solar Cell Rear Surface Segmentation
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Solution Overview
Problem
Conventional bifacial solar cells are costly and complex to manufacture, with limited photoelectric conversion efficiency due to lack of rear-surface passivation in crystalline silicon solar cells, and existing PERC solar cells face challenges in achieving high efficiency and low cost.
Innovation Solution
A bifacial punched PERC solar cell design featuring a rear silver busbar, rear aluminum finger, rear passivation layer, P-type silicon, N-type emitter, front passivation layer, and front silver busbar, with a light transmitting region penetrating both surfaces, allowing sunlight to be irradiated and reflected for enhanced efficiency, and a method involving laser grooving and passivation layer formation to reduce material usage and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rear-surface passivation is not provided in conventional crystalline silicon solar cells, then the manufacturing process remains simple, but the photoelectric conversion efficiency is limited due to high recombination rate at the rear surface
Solution Approach 1:
The patent divides the rear surface into distinct functional zones: a central light transmitting region (without passivation) and a peripheral region (with passivation). This segmentation allows the cell to simultaneously achieve high photoelectric conversion efficiency by enabling light transmission while controlling recombination through selective passivation at the edges where carriers are collected.
Solution Approach 2:
The patent applies different surface treatments to different regions of the rear surface. The central region maintains an unpassivated state to allow light transmission and carrier generation, while the peripheral region receives passivation treatment to reduce recombination losses. This local differentiation optimizes both light absorption and carrier collection efficiency.
2Manufacturing precision
If N-type silicon wafer is used for bifacial solar cell, then the photoelectric conversion efficiency is significantly increased, but the manufacturing cost becomes high and the process becomes complicated
Solution Approach 1:
Instead of using the conventional N-type silicon wafer approach, the patent inverts the strategy by using P-type silicon wafers and creating a bifacial structure through selective rear-surface treatment. This inversion maintains compatibility with established P-type manufacturing processes while achieving bifacial functionality, thereby reducing costs and process complexity.
Solution Approach 2:
The patent employs cost-effective P-type silicon wafers instead of expensive N-type wafers, and uses selective passivation techniques that can be implemented with existing manufacturing equipment. This approach prioritizes cost-effective solutions that achieve sufficient performance without requiring expensive materials or complex processes.
3Adaptability or versatility
If light transmitting region is created in the rear surface, then the bifacial functionality is enhanced, but the structural integrity and electrical connection may be compromised
Solution Approach 1:
The patent segments the rear surface into a central light transmitting region and a peripheral electrical connection region. This segmentation ensures that the light transmitting holes are concentrated in the center where they enhance bifacial functionality, while the peripheral region maintains continuous aluminum paste coverage for reliable electrical connections and structural integrity.
Solution Approach 2:
The patent applies different properties to different regions: the central region has high light transmissivity with minimal passivation to maximize bifacial effect, while the peripheral region has high electrical conductivity with full passivation to ensure reliable carrier collection. This local differentiation resolves the conflict between light transmission and electrical connection requirements.
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 significantly improves photoelectric conversion efficiency by 1%-10% at the rear side while reducing silver and aluminum paste usage, making the solar cell more affordable and easier to produce, thus addressing the challenges of high cost and complexity.
Implementation Method 1
a laser grooving region is formed in the rear passivation layer by laser grooving; the rear aluminum finger line is connected to the P-type silicon via the laser grooving region
Implementation Method 2
A crystalline silicon solar cell is a device that effectively absorbs solar radiation energy and converts light energy into electrical energy through the photovoltaic effect
Implementation Method 3
the bifacial PERC solar cell is provided with a light transmitting region penetrating front and rear surfaces of the cell
Implementation Method 4
surface passivation is basically only performed at the front surface, which involves depositing a layer of silicon nitride on the front surface of the silicon wafer via PECVD to reduce the recombination rate of the minority carriers at the front surface
Data Source
Figure 1~2
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Figure 5
AI summary
A bifacial punched PERC solar cell comprises a rear silver busbar (1), a rear aluminum finger (2), a rear passivation layer (3), a P-type silicon (4), an N-type emitter (5), a front passivation layer (6), a front silver finger (7), and a front silver busbar (8), a laser grooving region (9) is formed in the rear passivation layer by laser grooving; the rear aluminum finger line is connected to the P-type silicon via the laser grooving region, the bifacial PERC solar cell is provided with a light transmitting region (10) penetrating front and rear surfaces of the cell. A method of preparing a bifacial punched PERC solar cell and a module and a system employing the solar cell are also provided. The solar cell can be employed to increase back reflection for sunlight and significantly improve photoelectric conversion efficiency at the rear side of the cell.