Rectangular Solar Cell Division with Lateral Oxide Passivation
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Solution Overview
Problem
Solar cells with crystalline silicon substrates face electrical losses due to resistance in wiring when connected in series, and dividing the substrate to reduce area results in decreased fill factor and power output.
Innovation Solution
Forming a rectangular solar cell by dividing a square silicon substrate, with at least one principal surface covered by a thin-film and the second lateral surface exposed to an oxidizing atmosphere to form a non-natural oxide film, reducing electrical losses by minimizing current through the wiring member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the area of one solar cell is increased to reduce the number of cells needed, then the power per cell increases, but the current amount becomes larger resulting in increased electrical loss caused by wiring resistance
Solution Approach 1:
The patent divides a large-area silicon substrate into multiple smaller solar cells, each with optimized area. This segmentation allows the system to maintain high power output while keeping the current per cell manageable, thereby reducing electrical losses in wiring. The divided cells are then connected in series to achieve the desired total power.
Solution Approach 2:
The patent applies different treatments to different surfaces of the divided solar cells. Specifically, oxide films are formed on lateral surfaces that were created by division, while other surfaces maintain their original characteristics. This local differentiation optimizes electrical properties at critical interfaces without compromising overall cell performance.
2Loss of energy
If the silicon substrate is divided into two parts to reduce current and wiring loss, then electrical loss is reduced, but the fill factor decreases as compared to the solar cell before division
Solution Approach 1:
The patent performs preliminary actions before final cell division, including forming oxide films on lateral surfaces and applying appropriate coatings. These preliminary treatments ensure that when the substrate is divided, the resulting cells maintain optimal electrical characteristics and fill factor, compensating for the potential negative effects of division.
Solution Approach 2:
The patent modifies physical and chemical parameters of the solar cell surfaces, particularly by controlling oxide film thickness and composition on lateral surfaces. These parameter changes optimize the electrical properties of divided cells, maintaining high fill factor while benefiting from reduced current and wiring losses.
3Area of stationary object
If a thin-film is formed on the principal surface and extended onto lateral surfaces, then coverage is improved, but the second lateral surface formed by division remains uncovered requiring additional oxide film formation
Solution Approach 1:
The patent segments the film formation process into two distinct stages: first forming a thin-film on principal surfaces before division, then forming oxide films on lateral surfaces created by division. This segmentation allows each film type to be optimized for its specific location and function, simplifying the overall manufacturing approach despite the multiple steps.
Solution Approach 2:
The patent recognizes that different surfaces require different film treatments. Principal surfaces receive thin-film coverage optimized for light absorption and electrical properties, while lateral surfaces created by division receive oxide films optimized for passivation and electrical isolation. This local quality differentiation improves overall device performance while managing manufacturing complexity.
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 solution maintains or exceeds the power output of the original solar cell while reducing electrical losses, improving fill factor and open circuit voltage by minimizing current through the wiring member, thus enhancing power generation efficiency.
Implementation Method 1
When a lateral surface of a silicon substrate, which is formed at the time of dividing the silicon substrate, is covered with an oxide film, a passivation effect is obtained to provide a solar cell having characteristics equal to or higher than those before the division.
Implementation Method 2
At least one of the first principal surface and the second principal surface is covered with a thin-film. Examples of the thin-film that covers the principal surface of the silicon substrate include silicon-based thin-films and insulating material thin-films.
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4A~4B
AI summary
A solar cell (105) includes with a rectangular crystal silicon substrate (15). The crystal silicon substrate has a rectangular first principal surface (81) and a rectangular second principal surface (82). The first principal surface and/or the second principal surface is covered with a thin-film. The thin-film is formed so as to extend onto a first lateral surface (91), which is one of the lateral surfaces connecting one long side of the first principal surface and one long side of the second principal surface, and so as to not extend onto a second side surface (92), which is the other side surface. An oxide film (50) of silicon is formed over the whole thickness direction of the crystalline silicon substrate on the second lateral surface.