Selective Emitter Spot Layout for Metal Printing Alignment
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Solution Overview
Problem
The challenge in the manufacturing of high-efficiency selective emitter (SE) solar cells is to achieve precise alignment between laser spots and metal electrodes, as excessively large laser spots can reduce open-circuit voltage and power generation efficiency, while smaller spots require higher precision in alignment.
Innovation Solution
A method involving a silicon wafer with a textured and diffused surface, where laser spots are arranged in specific patterns along directions with varying areas to form spot rows and sub-spot regions, ensuring accurate alignment and reduced contact resistance between the metal electrode and the SE, even with deviations at the edge positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If laser spots are made larger to facilitate alignment between metal electrodes and laser spots, then alignment ease is improved, but open-circuit voltage and power generation efficiency deteriorate
Solution Approach 1:
The patent applies local quality by differentiating laser spot sizes across different regions of the silicon wafer. Specifically, laser spots near the edge of the wafer are made larger to accommodate alignment deviations caused by screen adhesive bonding, while laser spots in the center region maintain smaller sizes to preserve high open-circuit voltage and efficiency. This spatial variation in spot size optimizes both alignment tolerance and electrical performance in their respective locations.
2Power
If laser spots are made smaller to increase power generation efficiency, then power generation efficiency is improved, but alignment precision requirements increase
Solution Approach 1:
The patent implements local quality by creating region-specific laser spot patterns that match the local alignment requirements. In the center region where alignment is easier to control, small laser spots are used to maximize efficiency. Near the edges where screen printing deviations occur, larger laser spots provide tolerance for misalignment while maintaining acceptable efficiency through the gradual transition in spot size.
3Ease of manufacture
If uniform laser spot size is used across the entire silicon wafer, then manufacturing simplicity is improved, but alignment accuracy at edges deteriorates due to screen adhesive bonding deviations
Solution Approach 1:
The patent applies dynamics by making the laser spot size variable rather than static/uniform across the wafer. The spot size dynamically adapts to the local requirements: smaller in the center where precision is achievable and larger at the edges where tolerance is needed. This can be implemented through programmable laser systems that adjust spot parameters based on position, maintaining manufacturing feasibility while improving edge alignment.
Solution Approach 2:
The patent differentiates laser spot characteristics by location, creating local optimization zones. The gradual transition from small central spots to larger edge spots creates a gradient structure that locally addresses the specific alignment challenges at each position, balancing manufacturing simplicity with edge alignment accuracy.
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 method improves the alignment between the metal electrode and the SE, increasing the fill factor and efficiency of the solar cell by reducing contact resistance and accommodating deviations in the metal electrode position, thereby enhancing the overall power generation efficiency.
Implementation Method 1
illuminating the surface of the silicon wafer by laser spots to form the SE
Data Source
AI summary
A method for improving alignment between a selective emitters and metal printing, including: providing silicon wafer including first edge and midline parallel to the first edge; texturing and diffusing surface of the silicon wafer; and illuminating the surface of the silicon wafer by laser spots to form the SE. Multiple laser spots are arranged between the first edge and the midline to form spot rows, extension directions of the spot rows are parallel to the first edge, M spot rows are arranged and M is a positive integer and M>1. The M spot rows include N sub-spot regions, N is a positive integer and 1<N≤M, the sub-spot regions include at least one spot row, and areas of the laser spots in each sub-spot region are equal. The areas of the laser spots in different sub-spot regions from the midline pointing to the first edge gradually increases.