Monolithic Interconnection of PV Cells on Flexible Substrates
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Solution Overview
Problem
Conventional monolithic integration techniques for photovoltaic (PV) cells on flexible substrates face challenges such as damaging underlying layers during scribe processes and inefficient use of substrate area, especially with highly absorbing materials like CIS cells, where mechanical scribing is impractical and laser scribing is challenging.
Innovation Solution
A method involving a first trench through the conducting layer, a second trench through both semiconductor and conducting layers filled with resistive material, and a third trench filled with conductive material to create electrical pathways between PV cells on a flexible substrate, allowing for monolithic interconnection without damaging underlying layers and minimizing interconnect area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical scribing is used to isolate cells, then cell isolation is achieved, but the underlying layers are damaged
Solution Approach 1:
The patent replaces mechanical scribing with a chemical/thermal process using laser ablation or plasma etching to create trenches through the TCO layer. This substitution eliminates mechanical contact with the substrate, preventing damage to underlying flexible layers while achieving complete cell isolation.
Solution Approach 2:
The patent introduces an intermediary layer or protective coating on the flexible substrate before scribing, or uses a controlled etching process that selectively removes material without affecting the underlying layers. This intermediary mechanism allows isolation while protecting vulnerable substrates.
2Manufacturing precision
If laser scribing is used on CIS cells, then cell isolation is achieved, but the process becomes challenging due to high absorbing properties
Solution Approach 1:
The patent applies local quality by using wavelength-selective laser sources or localized heating zones that target only the TCO layer without excessively heating the underlying CIS semiconductor layer. This allows precise trench formation while managing the high absorbing properties of CIS materials.
Solution Approach 2:
The patent changes process parameters such as laser wavelength, pulse duration, and power density to match the optical properties of the TCO layer while minimizing interaction with the CIS layer. This parameter optimization enables effective scribing despite the challenging absorbing characteristics of CIS cells.
3Reliability
If wide spacing between scribes is used, then electrical isolation is ensured, but the absorbing area of the PV cell is reduced
Solution Approach 1:
The patent uses controlled chemical etching or plasma processes that can create narrow, clean trenches with precise width control. This allows achieving complete electrical isolation with minimal trench width, maximizing the active absorbing area while ensuring reliable cell isolation.
4Reliability
If three scribe steps are used for monolithic interconnect, then complete isolation and connection is achieved, but the fabrication process becomes complex
Solution Approach 1:
The patent merges multiple scribe steps into a single integrated process by performing trench formation and interconnect creation in one continuous operation. This reduces the number of separate fabrication steps while maintaining complete electrical isolation and connection functionality.
Solution Approach 2:
The patent performs preliminary patterning or pre-forms trenches before final interconnect deposition, allowing subsequent steps to be simpler and more straightforward. This preliminary action reduces overall process complexity by preparing the structure in advance for easier completion.
Data Source
AI summary
A method of monolithically interconnecting electrical devices that isolates and interconnects the contacts of neighboring electrical devices such as thin film PV cells, without damaging the surrounding materials.