Multi-junction Solar Cell Mesa Groove Edge Protection
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Solution Overview
Problem
Multi-junction solar cells face electrical degradation due to mechanical, chemical, and physical damage at the cell edges, which creates shunts and affects the fill factor, and existing edge protection methods are inadequate, especially in harsh environmental conditions like space applications.
Innovation Solution
A solar cell design featuring an inner mesa groove that encloses the active cell edge, filled with a non-conductive encapsulant, providing mechanical, chemical, and physical protection, and an antistatic coating to prevent electrostatic discharge, while maintaining electrical isolation and self-supporting integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the pn-junctions are exposed at the cell edge to enable manufacturing and electrical contact, then the manufacturing process is simplified and electrical connectivity is achieved, but the cell edge becomes vulnerable to mechanical, chemical, and physical damage that creates shunts and degrades electrical performance
Solution Approach 1:
The patent introduces an encapsulant material as an intermediary substance that fills the trench structure at the cell edge. This encapsulant acts as a mediator between the exposed pn-junctions and the harsh external environment, providing mechanical protection, chemical isolation, and physical shielding without interfering with the electrical functionality of the solar cell. The encapsulant fills the void space in the trench structure, creating a protective barrier that prevents damage to the pn-junctions while maintaining ease of manufacture.
2Strength
If a trench is etched into the wafer to protect pn-junctions from mechanical damage, then mechanical protection is provided, but the cell edge remains exposed to chemical and physical environmental attacks
Solution Approach 1:
The patent employs a composite protective structure consisting of the trench (mechanical barrier) combined with the encapsulant material (chemical and physical barrier). The trench provides structural strength and mechanical protection from physical impacts, while the encapsulant material filling the trench provides chemical isolation from environmental species and additional physical protection. This composite approach addresses multiple types of damage simultaneously - mechanical, chemical, and physical - that would be difficult to protect against with a single protective mechanism.
3Ease of manufacture
If the pn-junctions are located close to the cell surface to reduce manufacturing complexity, then the manufacturing process is simplified, but the fill factor is reduced due to edge damage acting as local shunts
Solution Approach 1:
The patent applies preliminary anti-action by pre-protecting the pn-junctions at the cell edge through the trench and encapsulant structure before any damage can occur. The encapsulant material is applied in advance to fill the trench and create a protective barrier, preventing mechanical, chemical, and physical damage from affecting the pn-junctions during operation. This preliminary protection measures maintains the simplified manufacturing approach with close pn-junction positioning while preventing the degradation that would otherwise reduce the fill factor.
Data Source
AI summary
A multi-junction solar cell includes a first main surface and a second main surface opposite to the first main surface of a semiconductor body. A topmost pn-junction of a plurality of pn-junctions stacked on top of each other adjoins to the first main surface. A cell edge of the semiconductor body defines a shape of the first and the second main surfaces. An encapsulant on the first main surface provides an environmental protection of the semiconductor body. A mesa groove is provided on the first main surface and penetrates at least the topmost pn-junction. The mesa groove is located adjacent to the cell edge and is created around the circumference of the semiconductor body for providing an inner cell area and a mesa wall, the mesa wall being created between the mesa groove and the cell edge. The mesa groove is filled with the encapsulant.