Bifacial Solar Cell Metallization Layout for Low-Silver Ribbon Bonding
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Solution Overview
Problem
Existing metallization layouts for bifacial solar cells, particularly HJT solar cells, face challenges in minimizing electrical resistances, maximizing the active area exposed to light, and reducing silver paste consumption while ensuring reliable electrical performance and efficient gluing or soldering of ribbons.
Innovation Solution
A novel metallization layout for bifacial solar cells that includes a grid structure with specific configurations of horizontal and vertical elements, allowing for efficient attachment of a ribbon using electrically conductive adhesive without the need for additional physical barriers or non-conductive layers, thereby optimizing silver paste usage and maintaining high electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If traditional metallization layouts with continuous bus bars are used, then reliable electrical connection and ribbon attachment are achieved, but silver paste consumption increases and manufacturing cost rises
Solution Approach 1:
The bus bar is segmented into multiple separate contact regions instead of a continuous structure. The first bus bar contact region and second bus bar contact region are divided and positioned at different locations, allowing the ribbon to bridge between them. This segmentation reduces the total silver paste area while maintaining electrical connectivity through the ribbon bridge.
Solution Approach 2:
The ribbon acts as an intermediary element that connects the segmented bus bar contact regions. Instead of using a continuous bus bar, the ribbon bridges the gap between the first and second bus bar contact regions, providing the necessary electrical connection while reducing silver paste consumption in the bus bar structure itself.
2Loss of substance
If bus bars have openings to save silver paste, then silver consumption decreases, but peeling resistance during heat treatment deteriorates
Solution Approach 1:
The bus bar structure is segmented into separate contact regions rather than being continuous with openings. This segmentation approach reduces silver paste area while avoiding the peeling issues associated with openings, as each contact region remains structurally intact and can maintain strong adhesion to the underlying electrode.
3Reliability
If additional physical barriers or non-conductive layers are added for ribbon attachment, then adhesion reliability improves, but device complexity and manufacturing steps increase
Solution Approach 1:
The metallization structure itself provides the adhesion function without requiring additional barrier layers or non-conductive materials. The segmented bus bar contact regions are designed to directly support ribbon attachment through their geometric configuration and material properties, allowing the structure to serve its own adhesion needs.
Solution Approach 2:
The bus bar contact regions serve multiple functions: electrical conduction, mechanical support, and adhesion substrate for the ribbon. By designing the metallization layout to fulfill all these functions simultaneously, additional specialized layers are eliminated, reducing overall device complexity.
4Reliability
If more silver paste is used for complete bus bar coverage, then electrical conductivity and connection reliability improve, but manufacturing cost increases
Solution Approach 1:
The bus bar is segmented into essential contact regions only, eliminating unnecessary continuous coverage. The first and second bus bar contact regions are positioned where electrical connection is most critical, concentrating silver paste usage in high-value areas while reducing overall quantity.
Solution Approach 2:
Different regions of the cell receive different metallization treatments. The bus bar contact regions have concentrated silver paste for high conductivity, while other areas have reduced or no metallization. This local quality approach optimizes silver usage by applying it only where electrically necessary.
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 proposed metallization layout achieves reduced silver consumption by up to 10%, maintains reliable electrical performance, and ensures strong adhesive bonding with minimal adhesive usage, thus enhancing the efficiency and cost-effectiveness of solar cell modules.
Implementation Method 1
the pyramids allow both to reduce the reflectivity of the surface and to reduce the scattering of the light at small angles, in order to increase the optical path within the wafers
Implementation Method 2
A-Si:H layers are deposited on both sides of the c-Si wafer to passivate its surface, reducing silicon dangling bonds on the crystalline silicon wafer surface
Implementation Method 3
n-type silicon wafers are usually employed to reach high efficiencies and, in these particular cases, the minority carriers are holes
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
The present invention concerns a bifacial solar cell (1) comprising a front side (10) and a back side (20), said front and back sides (10, 20) having a respective outer layer (34) made of transparent conductive oxide, on which is placed a respective metallization grid (11, 21), each metallization grid (11, 21) comprising first collectors (111, 211) running parallel to each other in a horizontal direction (x) of said solar cell (1) and second collectors (112, 212) crossing said first collectors (111, 211), each second collector (112, 212) comprising two vertical elements (112a, 112b, 212a, 212b) and at least one horizontal element (112c, 212c) every one or two first collectors (111) or 3 or 6 first collectors (211) connecting said two vertical elements (112a, 112b, 212a, 212b), wherein said metallization grids (11, 21) furtherly comprise at least one respective front or back area (113, 213), said front or back area (113, 213) comprising said at least one horizontal element (112c, 212c) and a portion of the underlying outer layer (34) made of transparent conductive oxide, so that a cell connector can be attached to said solar cell (1) by means of an electrically conductive adhesive deposited on said front or back area (113, 213) without needing a physical barrier for said electrically conductive adhesive. The present invention also concerns a solar cell module and a method of manufacturing thereof.