Substrate-incident laser scribing for thin film solar cell patterning
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Solution Overview
Problem
The existing mechanical scribing methods for manufacturing thin film solar cells are inefficient due to high equipment costs, increased defective products, and difficulty in reducing line width, leading to decreased productivity and photovoltaic conversion efficiency.
Innovation Solution
A method using a substrate-incident laser for patterning in the scribing process of thin film solar cells, employing a double-layered rear electrode with a transparent conductive oxide and a metal layer to improve precision and reduce heat transfer, allowing for the use of a less expensive nanosecond pulse laser and preventing interference during CIGS deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a mechanical scribing method is used for patterning in the scribing process, then equipment costs are reduced, but productivity decreases and defective products increase due to scribing tip abrasion
Solution Approach 1:
The patent replaces the mechanical scribing system with a laser-based scribing system. The laser beam is focused through the transparent substrate to ablate the rear electrode and thin film layers, eliminating mechanical contact and tip abrasion. This substitution maintains low equipment costs while significantly improving productivity and reducing defective products.
2Ease of manufacture
If a mechanical scribing method is used, then equipment costs are reduced, but manufacturing precision deteriorates due to difficulty in decreasing line width
Solution Approach 1:
The mechanical scribing system is replaced with a laser scribing system that uses a focused laser beam to achieve precise patterning. The laser beam can be focused to a very small spot size, enabling line widths well below what is achievable with mechanical scribing, thereby improving manufacturing precision while maintaining cost-effectiveness.
Solution Approach 2:
The patent changes the fundamental parameter of the scribing process from mechanical contact to optical energy concentration. By controlling laser parameters such as wavelength, pulse duration, and focus spot size, the system achieves superior line width control and patterning precision that cannot be obtained with mechanical methods.
3Manufacturing precision
If a laser is incident from the transparent window layer for scribing, then manufacturing precision is improved, but heat transfer to the Mo rear electrode increases causing loss of the rear electrode
Solution Approach 1:
Instead of incident the laser from the window layer side, the patent inverts the approach by incidenting the laser from the rear surface of the substrate. The laser beam passes through the transparent substrate and directly ablates the rear electrode and thin film layers from below, achieving precise patterning while minimizing heat transfer to the Mo rear electrode that needs to be preserved.
Solution Approach 2:
The transparent substrate acts as an intermediary medium that allows the laser beam to pass through to the rear electrode without significant heat absorption. The substrate transmits the laser energy to the target layers while protecting the Mo rear electrode from excessive heat transfer, enabling precise scribing with minimal collateral damage.
4Loss of energy
If a pulse laser with pulse width below several ten picoseconds is used, then heat transfer to the Mo rear electrode is reduced, but manufacturing costs increase due to expensive laser equipment
Solution Approach 1:
By inverting the laser incident direction to come from the substrate rear surface, the patent achieves efficient scribing with longer pulse width lasers (nanosecond range). This approach allows the laser energy to be directly absorbed by the rear electrode and thin film layers without requiring ultra-short pulse widths, thereby using less expensive laser equipment while still minimizing heat transfer to the Mo rear electrode.
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 productivity, reduces manufacturing costs, and maintains high photovoltaic conversion efficiency while enabling light transmission and aesthetic adjustments for transparent window applications.
Implementation Method 1
performing a second patterning process P2 after deposition of CIGS/CdS/i-ZnO, and performing a third patterning process P3 after deposition of TCO... performing a second laser scribing process by inputting a laser to a second surface of the transparent substrate... to separate the light absorption layer
Implementation Method 2
employing a double-layered rear electrode with a transparent conductive oxide and a metal layer to improve precision and reduce heat transfer, allowing for the use of a less expensive nanosecond pulse laser and preventing interference during CIGS deposition
Implementation Method 3
forming a CIGS thin film (or, a CZTS thin film) as a p-type light absorption layer... high photovoltaic conversion efficiency (PCE) of 20% or above
Data Source
AI summary
A method for manufacturing a thin film solar cell includes: depositing a transparent first rear electrode on a first surface of a transparent substrate; depositing a second rear electrode having a high-conductive metal on the first rear electrode; performing a first laser scribing process to separate a double layer of the first and second rear electrodes; depositing a light absorption layer having selenium (Se) or sulfur (S) on the second rear electrode; performing a second laser scribing process by inputting a laser to a second surface of the transparent substrate to separate the light absorption layer; depositing a transparent electrode on the light absorption layer; and performing a third laser scribing process by inputting a laser to the second surface to separate the transparent electrode. Accordingly, patterning may be performed in a substrate-incident laser manner to improve price, productivity and precision of the patterning process.