Solar Cell Shading Loss via Local Doping
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Solution Overview
Problem
Conventional solar cell modules experience significant power generation performance loss when solar cells are shaded, as the entire string unit is bypassed, leading to reduced output from unshaded cells within the same string unit.
Innovation Solution
A solar cell design featuring a n-type silicon substrate with a low-doped region and a highly doped region, where the highly doped region has a higher dopant concentration than the low-doped region, allowing electric current to flow to shaded solar cells at a lower voltage drop, thereby minimizing power generation loss when cells are shaded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bypass diode is connected in parallel to a string unit, then the string unit can be bypassed when solar cells are shaded, but the power generation performance of unshaded cells within the string unit is reduced
Solution Approach 1:
The patent applies local quality by creating a highly doped region at a specific location within the solar cell structure - between the low-doped region and the amorphous silicon layer. This localized high-doping area generates a strong internal electric field that enables selective current transport, allowing shaded cells to contribute to power generation while maintaining overall module reliability. The local modification of dopant concentration resolves the contradiction by enabling both bypass functionality and continued power generation from unshaded cells within the same string unit.
2Power
If the dopant concentration in the silicon substrate is increased, then the voltage drop is reduced allowing current to flow to shaded cells, but the manufacturing complexity increases
Solution Approach 1:
Instead of uniformly increasing dopant concentration throughout the entire silicon substrate, the patent applies local quality by creating a highly doped region only in the specific area between the low-doped region and the amorphous silicon layer. This localized approach reduces the voltage drop and enables current flow to shaded cells while minimizing the overall manufacturing complexity compared to full-substrate high-doping processes.
Solution Approach 2:
The patent segments the silicon substrate into distinct doping regions - a low-doped region and a highly doped region - rather than using a uniform doping structure. This segmentation allows the highly doped region to perform the specific function of reducing voltage drop and enabling current flow to shaded cells, while the rest of the substrate maintains its original doping characteristics, thereby reducing overall 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 design effectively reduces output loss in solar cell modules when cells are shaded, as more unshaded cells within the string unit can contribute to power generation, maintaining performance compared to conventional modules.
Implementation Method 1
a first main-surface side highly doped region provided between the low-doped region and the second conductive-type amorphous silicon layer and having a concentration of a first conductive-type dopant higher than that in the low-doped region
Data Source
Figure 1
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AI summary
An n-type silicon substrate 1 is provided with a lightly doped region 11, and a first main surface-side highly doped region 12 having an n-type dopant concentration that is higher than that of the n-type lightly doped region 11. The first main surface-side highly doped region 12 is disposed between the n-type lightly doped region 11 and a p-type amorphous silicon layer 3.