Removal Mechanism and Defect Characterization for Glass-Side Laser Scribing of CdTe/CdS Multilayer in Solar Cells

Abstract

Laser scribing is an important manufacturing process used to reduce photocurrent and resistance losses and increase solar cell efficiency through the formation of serial interconnections in large-area solar cells. High-quality scribing is crucial since the main impediment to large-scale adoption of solar power is its high production cost (price-per-watt) compared to competing energy sources such as wind and fossil fuels. In recent years, the use of glass-side laser scribing processes has led to increased scribe quality and solar cell efficiencies, however, defects introduced during the process such as thermal effect, micro cracks, film delamination, and removal uncleanliness keep the modules from reaching their theoretical efficiencies. Moreover, limited numerical work has been performed in predicting thin film laser removal processes. In this study, a nanosecond (ns) laser with a wavelength at 532nm is employed for pattern 2 (P2) scribing on CdTe (Cadmium telluride) based thin-film solar cells. The film removal mechanism and defects caused by laser-induced micro-explosion process are studied. The relationship between those defects, removal geometry, laser fluences and scribing speeds are also investigated. Thermal and mechanical numerical models are developed to analyze the laser-induced spatio-temporal temperature and pressure responsible for film removal. The simulation can well-predict the film removal geometries, generation of micro cracks, film delamination and remaining materials. The characterization of removal qualities will enable the process optimization and design required to enhance solar module efficiency.

Laser Forming of Sandwich Panels With Metal Foam Cores

“…Cohesive surfaces have the same thermal capabilities but also allow for delamination to occur when specified damage parameters are exceeded [24]. The same result can be achieved by inserting a thin layer (e.g., 10 lm) at the interface consisting of cohesive elements, with the additional benefit that delamination can be monitored and visualized [25]. Even though delamination did not occur in the current study, this approach was used for both interfaces, in anticipation of future studies where delamination effects become important.…”

Laser Scribing of Photovoltaic Solar Thin Films: A Review

“…Thermal stress, delamination, and cracking are other common phenomena that can be generated due to the localized temperature rise and thermal expansion in thin-film laser scribing. The significance of this phenomenon stems from its negative impact on power efficiency, cell viability, and photocurrent generation [92,93]. Using a ns laser source for P3 ablation in a-Si solar cells has shown irregular scribe boundaries with peeling of the film [94].…”

“…In this case, using infrar and high laser power increased delamination and elevated the molten r rounding edges in ps laser scribing [98]. Using glass-side laser ablation p delamination and microcracks due to the pressure created by the plas which caused shockwave formation, film deformation, and brittle material findings show that crack formation can also depend on the obtained g groove shapes with sharp vertical edges are more prone to void formation peeling-off in the deposited material than gradually sloped edge scribes [5 Delamination can also be created in CdTe solar cell P2 lift-off ablatio CdTe and CdS layers [93]. The weak adhesion between the layers can cause ination.…”

Overview of Laser Applications in Manufacturing and Materials Processing in Recent Years

“…The second and third models use solid material properties. To model the interfaces of sandwiches, an exceedingly thin layer at the interface consisting of cohesive elements is inserted, with the additional benefit that delamination can be monitored and visualized [206], even though delamination normally does not occur in laser forming. Closed-cell AlSi7 foam was used.…”