Embedded TCO Grid and Laser Sealing for Solar Cell Substrates
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Solution Overview
Problem
Dye-sensitized solar cells (DSCs) face challenges with low conductivity of transparent oxide layers on glass substrates, leading to high internal resistances and reduced fill factor when scaling up, which limits their efficiency and requires additional manufacturing steps for collecting lines that waste illuminated area and are costly.
Innovation Solution
The integration of a network of highly conductive metal lines beneath the transparent conductive oxide (TCO) layer on glass substrates, known as embedded TCO (ETCO), which collects electrons and reduces the need for external collecting lines, combined with a laser-assisted low-temperature glass paste sealing process to enhance module stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional TCO layer is applied on glass substrate, then the substrate provides insulation and basic conductivity, but the internal resistance is high and fill factor is reduced when scaling up
Solution Approach 1:
The patent applies a composite structure combining TCO layer with embedded metal lines (silver paste or aluminum) within grooves of the glass substrate. This composite configuration provides both the insulating properties of glass and the high conductivity of metal, resolving the contradiction between maintaining substrate insulation and reducing internal resistance for scaled-up modules
Solution Approach 2:
The invention introduces conductive metal lines only in specific locations where current collection is needed, rather than making the entire substrate conductive. The metal lines are embedded in grooves at strategic positions to collect current from the TCO layer, providing local enhancement of conductivity where required while maintaining overall substrate insulation
2Object-generated harmful factors
If additional collecting lines are added to reduce internal resistance, then conductivity improves, but the illuminated area is reduced and manufacturing cost increases
Solution Approach 1:
The patent merges the functions of current collection and substrate structure by embedding the collecting lines within grooves of the glass substrate itself. This integration allows the substrate to serve dual purposes: providing mechanical support/insulation while simultaneously housing the conductive elements, thereby minimizing the space required for current collection and maximizing illuminated area
3Ease of manufacture
If conventional sealing processes are used, then substrates can be joined, but long-term stability is insufficient
Solution Approach 1:
The patent replaces conventional mechanical or thermal sealing processes with laser-assisted sealing. The laser provides precise, localized heating that melts and fuses the glass substrates and sealing material along the welding line, creating a hermetic seal with superior long-term stability compared to traditional sealing methods
4Strength
If laser beam is applied for sealing, then sealing strength improves, but heat concentration may cause instability in welding line
Solution Approach 1:
The patent employs a reciprocating laser beam that moves back and forth along the sealing line in periodic cycles. This periodic action distributes heat accumulation along the welding path, preventing localized overheating and maintaining stable welding conditions while still achieving strong sealing through repeated thermal cycles
Solution Approach 2:
The reciprocating laser beam maintains continuous engagement with the sealing material along the entire welding line, ensuring uniform heat distribution and consistent sealing quality. The continuous back-and-forth motion prevents gaps or weak points in the seal while maintaining steady thermal processing conditions
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
The ETCO approach improves electrical conductivity and reduces internal resistances, allowing for more efficient solar energy collection and easier module assembly, while the laser-assisted sealing enhances the long-term stability and performance of DSC modules.
Implementation Method 1
laser welding the two substrates by means the previously deposited sealing material (4)
Implementation Method 2
A laser beam is used to support the glass melting and subsequent sealing of the module
Implementation Method 3
embedding or depositing on one or both of the mentioned substrates a conductive mesh able to carry current for the cell exterior
Implementation Method 4
substrates coated with a transparent conductive oxide (TCO) are improved to allow a greater electronic conductivity
Data Source
Figure 1~3
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Figure 6~7
AI summary
Solar cells use as substrates glass (23) coated with a transparent conductive layer (21), able to collect the electric power generated by the solar cell. This layer (21), normally a TCO, have limited conductivity, implying the use of current collector lines applied in a complex manner. The conductivity of the conductive layer (21) is increased by the application of a structure, in particular a grid, of thin conductive lines (22) inserted in grooves on the glass surface (23) or directly applied on this, followed by a TCO layer coating (21). This highly conductive grid (22) collects the electricity from the TCO layer (21) and directs it to the periphery of the cell. Both glass substrates are sealed by a process employing a precursor of glass surrounding the entire perimeter of the substrate. The glass precursor is heated to its melting point, by a laser, completely sealing the two substrates of the module.