Crystalline Silicon Solar Cell Copper Back Electrode Insulation
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Solution Overview
Problem
Conventional hetero-junction solar cells using copper as a back electrode face challenges with copper diffusion into the silicon substrate, leading to characteristic deterioration, especially when exposed to environmental tests, due to the high diffusion velocity of copper in silicon and the lack of effective insulating treatments.
Innovation Solution
A method for producing crystalline silicon solar cells where the back electrode layer containing copper is formed on the entire back surface, and a laser beam is irradiated from the front surface to prevent copper diffusion, forming an insulating region along the outer peripheral part of the substrate to prevent short circuits and maintain solar cell performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If copper is used as the back electrode layer to reduce material costs, then manufacturing cost is reduced, but copper diffusion into the silicon substrate occurs leading to characteristic deterioration
Solution Approach 1:
An insulating layer is introduced as an intermediary between the copper back electrode layer and the silicon substrate. This mediator prevents copper diffusion into the silicon while allowing the copper layer to maintain its electrical function, thus resolving the contradiction between cost reduction and reliability maintenance
Solution Approach 2:
The back electrode structure is segmented into multiple functional layers: the copper layer for electrical conductivity and cost-effectiveness, and a separate insulating layer for diffusion prevention. This segmentation allows each layer to perform its specific function without interfering with the other, maintaining both cost advantages and reliability
2Reliability
If laser beam irradiation is applied from the back surface to form separation grooves, then insulation treatment is achieved, but copper is blown off and diffuses into the silicon substrate
Solution Approach 1:
Instead of irradiating the laser beam from the conventional back surface direction, the invention inverts the irradiation direction to apply the laser beam from the front surface. This reversal prevents copper blow-off while achieving the desired separation groove formation and insulation effect
Solution Approach 2:
The insulating layer is formed preliminarily before laser irradiation to create a protective barrier. This preliminary anti-action prevents copper diffusion that would otherwise occur during the laser processing step, counteracting the harmful effect before it can manifest
3Reliability
If mask processes are used to prevent silicon thin film extension to surfaces, then leak prevention is improved, but mass productivity deteriorates due to increased process complexity
Solution Approach 1:
The complex mask processes are extracted and replaced by a simpler insulating layer formation step. The insulating layer inherently prevents silicon thin film extension to surfaces without requiring multiple masking operations, thus maintaining leak prevention while improving mass productivity
Solution Approach 2:
The manufacturing approach changes from a process-intensive method (multiple mask steps) to a material-based solution (insulating layer). This parameter change in the manufacturing strategy simplifies the process flow and enhances productivity while maintaining the required leak prevention performance
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 effectively prevents copper diffusion into the silicon substrate, maintaining the solar cell's characteristics and efficiency even when using copper as the primary material in the back electrode, thus enhancing the long-term performance and reducing material costs.
Implementation Method 1
a laser beam is irradiated from the front surface to prevent copper diffusion, forming an insulating region along the outer peripheral part of the substrate
Data Source
Figure 1~2
Figure 3
Figure 4A~4E
AI summary
The present invention provides a method for producing a crystalline silicon solar cell (1) with a high conversion efficiency and having a precisely machined light-incident surface. The method includes a first transparent electrode layer forming step of forming a first transparent electrode layer (6), a back electrode layer forming step of forming a back electrode layer (11) containing copper as a major ingredient on a substantially entire area of a surface of a second main surface side, and an insulating step of forming an insulating region (30) so as to remove a short circuit between at least the first transparent electrode layer (6) of the first main surface side and at least a second transparent electrode layer (10) and the back electrode layer (11) of the second main surface side, and performs the insulating step after the first transparent electrode layer forming step and the back electrode layer forming step. The insulating step includes a step of irradiating a laser beam along an entire periphery of an outer peripheral part of the first main surface onto a position within 3 mm from an outer peripheral end face of a one conductivity-type single crystalline silicon substrate (2) from the first main surface side.