FINE LINE PRINTING: HOW TO REDUCE CONTACT SHADOWING WITHOUT INCREASE SERIESRESISTANCE

摘要

This paper presents results obtained on fine line screen printing on large area (100 cm2) silicon solar cells.Aim of the work is to reduce contact shadowing by matching the screen printing technology, which is a localized and lowcost technique, with the buried contact one, to get a cost effective way to overcome the limitations of both technologies.To get fine line printing (<100 mm), several kinds of innovative laser cut stencils and meshed screens, with fine polymeric(instead of conventional steel) wire and high mesh number, have been tested: at laboratory scale, line width of 50 - 60 mmhave been obtained. Silver based inks from different suppliers have been tested, as proper rehology of the pastes is acrucial requirement for fine line printing; optimization of printing parameters, such as snap off distance, squeegee speedand pressure has been performed: on planar devices, fired fingers width of 60 mm have been obtained. Moreover, aseffectiveness of screen-printed buried contacts in terms of gain in Jsc values can be demonstrated only after achieving afine line printing into the grooves, this technique has been optimized on buried grids. Fine-line screen printing technologyhas been optimized on buried contact, mechanically and laser grooved structures: buried contact, screen printed contacts,100 cm2 solar cells have been fabricated, showing good PV performances.