Pattern Transfer Printing of Ultrafine PV Lines With Laser Release
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Solution Overview
Problem
Current printing technologies face challenges in producing ultra-fine metal finger lines for photovoltaic cells, particularly in achieving high aspect ratios and low line and contact resistance.
Innovation Solution
The proposed pattern transfer printing (PTP) method involves using a tape with pattern transfer sheets having trenches filled with a uniform paste mixture of conductive printing pastes with different particle sizes or containing a NIR absorbing dye, which is released onto wafers upon laser illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If screen printing is used to print metal finger lines, then the printing process is simple and established, but the ability to print ultra-fine lines with high aspect ratio is limited
Solution Approach 1:
The printing process is segmented into two distinct stages: (1) paste filling into trenches on a donor substrate, and (2) laser-induced transfer to the receiving substrate. This segmentation allows each stage to be optimized independently - the filling stage uses simple dispensing while the transfer stage uses controlled laser irradiation to achieve ultra-fine line precision
Solution Approach 2:
A donor substrate with pre-formed trenches serves as an intermediary carrier for the metal paste. The paste is first deposited into the trenches on the donor substrate, then transferred to the receiving substrate via laser irradiation. This intermediary approach enables precise pattern definition and ultra-fine line printing that cannot be achieved directly through screen printing
2Manufacturing precision
If line width is reduced to 10 microns or less, then the aspect ratio and contact area are improved for cell efficiency, but the line and contact resistance increases
Solution Approach 1:
The paste composition parameters are changed by incorporating bimodally dispersed metal particles with two distinct size ranges. This dual-size particle system allows the paste to form both narrow lines (10 microns or less) and maintain low resistance through the synergistic packing and conductivity properties of the mixed particle sizes
Solution Approach 2:
The conductive paste uses a composite particle size distribution rather than uniform particles. The bimodal distribution combines fine particles for filling small features and coarser particles for maintaining conductivity pathways, enabling ultra-fine lines with low resistance
3Stability of the object's composition
If uniform paste mixture with different particle sizes is used, then the filling uniformity and transfer consistency are improved, but the paste formulation complexity increases
Solution Approach 1:
The paste formulation uses controlled particle size distribution parameters with bimodal dispersion. By specifying particular size ranges for the two particle populations and their relative proportions, the paste achieves uniform mixing and consistent transfer behavior while maintaining a manageable formulation 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
This method enables the production of highly accurate, ultra-fine conductive lines with high aspect ratios and low waviness, reducing the required laser power and minimizing debris, thus improving the efficiency and cost-effectiveness of photovoltaic cell manufacturing.
Implementation Method 1
transferred the paste mixture from the pattern transfer sheets onto the delivered wafers, by releasing the paste mixture from the trenches upon illumination by a laser beam
Data Source
AI summary
Pattern transfer printing (PTP) methods are provided, which comprise: (i) handling a tape with multiple pattern transfer sheets having patterns of trenches, to controllably deliver the pattern transfer sheets for paste filling and consecutively for pattern transfer, (ii) mixing, continuously and uniformly, at least two types of conductive printing pastes having different particle sizes and/or at least one type of conductive printing paste with a NIR (near infrared) absorbing dye—to form a uniform paste mixture, (iii) filling the trenches on the delivered pattern transfer sheets with the paste mixture, (iv) controllably delivering wafers for the pattern transfer, and (v) transferring the paste mixture from the pattern transfer sheets onto the delivered wafers, by releasing the paste mixture from the trenches upon illumination by a laser beam. The methods yield highly accurate, ultrafine conductive lines, e.g., for photovoltaic (PV) applications.