Back Contact Solar Cell Electrode Overlap Design
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Solution Overview
Problem
The manufacturing method of backside contact solar cells faces challenges in maintaining high photoelectric conversion efficiency due to deviations between base layers and base electrodes, particularly when using the printing method, which is difficult to stabilize with narrow electrode widths, and increasing base layer width reduces efficiency.
Innovation Solution
A solar cell design where part of the base collecting electrode is also arranged on the emitter layer adjacent to the base layer, allowing for increased positional deviation tolerance without widening the base layer, and using a screen printing method for electrode formation with film thickness and width of 0.1 to 10 μm to maintain high contact resistance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the base layer width is increased to reduce positional deviation between base layer and base electrode, then the manufacturing precision is improved, but the photoelectric conversion efficiency deteriorates
Solution Approach 1:
The base collecting electrode is extended onto the emitter layer in the lateral dimension, creating an overlapping region where the electrode contacts both the base layer and emitter layer. This dimensional extension allows the electrode to accommodate positional deviations without requiring an increased base layer width, thereby resolving the contradiction between manufacturing precision and photoelectric conversion efficiency.
Solution Approach 2:
The base collecting electrode is designed with non-uniform width, being wider in regions where it overlaps with the emitter layer and narrower where it contacts only the base layer. This local variation in electrode width provides tolerance for positional deviations at critical interfaces while maintaining optimal base layer dimensions for high photoelectric conversion efficiency.
2Ease of manufacture
If the printing method is used for electrode formation to reduce manufacturing cost, then the ease of manufacture is improved, but the manufacturing precision deteriorates due to plate elongation variations
Solution Approach 1:
The base collecting electrode is designed with variable width parameters - wider in the overlapping region with the emitter layer and narrower in other regions. This parameter variation compensates for plate elongation effects in the printing process, allowing cost-effective printing methods to achieve acceptable precision by accommodating dimensional variations through the electrode's geometric design.
3Reliability
If the base collecting electrode is made wider to ensure good contact with the base layer, then the electrical conductivity is improved, but the photoelectric conversion efficiency deteriorates due to increased shadowing loss
Solution Approach 1:
The base collecting electrode utilizes the vertical dimension by extending onto the emitter layer, creating an overlapping contact region. This allows the electrode to achieve good electrical contact through the combined contact area on both base layer and emitter layer without increasing the horizontal width that would cause shadowing losses, thus resolving the contradiction between reliability and energy efficiency.
Data Source
AI summary
Provided is a solar cell including, on a first main surface of a semiconductor substrate having a first conductivity type, a base layer which has the first conductivity type, and an emitter layer which is adjacent to the base layer and has a second conductivity type which is a conductivity type opposite to the first conductivity type, and further including a base collecting electrode provided on at least the base layer, and a part of the base collecting electrode is also arranged on the emitter layer adjacent to the base layer on which the base collecting electrode is arranged. Consequently, the inexpensive solar cell having high photoelectric conversion efficiency can be provided.