Solar Cell Rear Metallization Segmentation
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Solution Overview
Problem
Conventional solar cells face high silver consumption and damage to backside passivation due to full rear side solder pads, requiring multiple pads or busbars for reliability, which is inefficient and stressful during soldering.
Innovation Solution
The use of isolated, miniature sub-pads instead of full area rear side solder pads, with a dielectric layer structure and partial solder pads of various shapes, such as dots or polygons, to reduce silver consumption and improve stress distribution during soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full area rear side solder pads are used, then module reliability is ensured, but silver consumption increases significantly and backside passivation is damaged
Solution Approach 1:
The patent divides the continuous rear side solder pad into multiple discrete sub-pads arranged in a pattern. This segmentation reduces the total silver area while maintaining electrical connectivity and mechanical reliability through the distributed pad structure, directly addressing the contradiction between reliability and silver consumption.
Solution Approach 2:
The patent applies different properties to different regions: sub-pads are provided only in specific regions rather than uniformly across the entire rear side. This local quality approach allows silver to be concentrated where most needed for reliability while minimizing overall consumption, and preserves passivation in areas where sub-pads are not placed.
2Reliability
If multiple rear side solder pads are used to ensure reliability, then module reliability improves, but surface recombination area increases
Solution Approach 1:
By segmenting the solder pad structure into discrete sub-pads, the patent reduces the continuous metal surface area that causes surface recombination. The segmented structure maintains reliability through multiple contact points while minimizing the harmful surface recombination effect compared to a single large pad.
3Reliability
If full area rear side solder pads are used, then electrical conductivity is ensured, but stress distribution during soldering deteriorates
Solution Approach 1:
The segmentation of the solder pad into multiple sub-pads creates a distributed stress pattern during soldering, similar to a nail bed distribution. This prevents stress concentration that would occur with a single large pad, improving stress distribution while maintaining electrical conductivity through the multiple sub-pad connections.
4Device complexity
If rear side solder pads are made larger to reduce pad density, then manufacturing complexity decreases, but silver consumption increases
Solution Approach 1:
The patent applies partial action by providing sub-pads only in specific regions rather than uniformly across the entire rear side. This selective placement reduces the total silver area compared to uniform large pads while maintaining adequate electrical and mechanical performance in the critical regions where sub-pads are placed.
Data Source
Figure 1
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Figure 3A~3E
AI summary
Various embodiments provide a solar cell (100). The solar cell (100) includes a substrate (108) having a front side (102) and a rear side (104). At least the front side (102) receives light. The solar cell (100) further includes a multiplicity of rear side solder pad regions (120) at least partially arranged over the rear side (104), and a plurality of partial solder pads (122, 300, 310, 320, 330, 340, 360, 370) formed in each rear side solder pad region (120) of the multiplicity of rear side solder pad regions (120). Each partial solder pad includes a first metal. The partial solder pads in a respective rear side solder pad region (120) are separated (124) from each other. The solar cell (100) further includes a rear side metallization (126) formed at the rear side (104) of the substrate (100) partly overlapping the partial solder pads, the rear side metallization (126) including a second metal different from the first metal.