TOPCon Solar Cell Rear Texture for Borosilicate Glass Removal

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Solution Overview

Problem

The existing manufacturing process for N-type tunnel oxide passivated contact (TOPCon) solar cells faces challenges in removing borosilicate glass, leading to increased contact resistivity and fluctuations in fill factor, which affects the photoelectric conversion efficiency due to the difficulty in polishing the rear surface structure.

Innovation Solution

The implementation of a solar cell design with texture structures on both the front and rear surfaces, featuring a pyramid-shaped microstructure on the front and a non-pyramid-shaped microstructure on the rear, along with specific passivation layers, to improve open-circuit voltage and reduce contact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If borosilicate glass is formed by boron diffusion on the rear surface of the silicon wafer, then the tunnel oxide passivated contact structure is achieved, but the glass is more difficult to be removed compared with phosphorosilicate glass

Engineering Contradiction:

Improvepassivation performanceVSAvoiddifficulty of removing borosilicate glass

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent divides the rear surface texture structure into multiple stacked substructures (first substructures and second substructures) with different geometries. This segmentation allows the surface to be processed in a controlled manner, enabling effective removal of borosilicate glass while maintaining the desired texture for passivation performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different texture structures to different regions of the rear surface. The first substructures have one-dimensional sizes of 5-20 μm while the second substructures have one-dimensional sizes of 20-45 μm. This local variation in texture characteristics enables optimized glass removal in different areas while maintaining overall passivation effectiveness.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the rear surface is polished with acid additive to achieve a flat structure, then the surface is cleaned, but the polished structure directly affects the manufacturing of the tunnel oxide layer and polycrystalline silicon layer

Engineering Contradiction:

Improveflatness of rear surfaceVSAvoidpassivation performance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent controls specific parameters of the texture structure to resolve the contradiction between flatness and passivation performance. The first substructures have one-dimensional sizes of 5-20 μm and the second substructures have one-dimensional sizes of 20-45 μm, with vertical distances between adjacent substructures of 0.5-2 μm. These parameter specifications enable the surface to provide both adequate flatness for tunnel oxide layer manufacturing and sufficient texture for passivation performance.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the one-dimensional size of the top surface of the outermost first substructure is controlled to be less than or equal to 45 μm, then the uniformity of the tunnel oxide layer is enhanced, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveuniformity of tunnel oxide layerVSAvoidcontrol of texture structure dimensions

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent implements a two-tier texture structure where first substructures (5-20 μm) and second substructures (20-45 μm) serve different functional roles. The smaller first substructures provide localized areas for uniform tunnel oxide layer formation, while the larger second substructures provide overall surface coverage and structural support. This local quality differentiation reduces the manufacturing precision burden compared to uniform small-scale structures.

Inventive Principle:

Principle #3Local quality

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 enhances the uniformity of the tunnel oxide layer, reduces contact resistivity, and improves the fill factor and photoelectric conversion efficiency of the solar cell by controlling the texture structure dimensions and passivation layer thickness.

Implementation Method 1

An N-type tunnel oxide passivated contact (TOPCon) solar cell relies on a 'tunnel effect' to achieve passivated contact on a rear surface of the solar cell

Methodology Applied

Scientific EffectTunnel effect:

Data Source

PatentUS11843071B2Solar cell, manufacturing method thereof, and photovoltaic module

Publication Date: 2023.12.12 SHANGHAI JINKO GREEN ENERGY ENTERPRISE MANAGEMENT CO LTD

AI summary

Provided are a solar cell, a manufacturing method thereof, and a photovoltaic module. The solar cell includes: a semiconductor substrate, in which a rear surface of the semiconductor substrate having a first texture structure, the first texture structure includes two or more first substructures at least partially stacked on one another, and a one-dimensional size of the top surface of the outermost first substructure is less than or equal to 45 μm; a first passivation layer located on a front surface of the semiconductor substrate; a tunnel oxide layer located on the first texture structure; a doped conductive layer located on a surface of the tunnel oxide layer, the doped conductive layer includes a P-type doped conductive layer and an N-type doped conductive layer; and a second passivation layer located on a surface of the doped conductive layer.