Optimized Adhesion of Plated Silicon Solar Cell Contacts by F_2-Based Dry Atmospheric Pressure Nano-Roughening

摘要

The adhesion of a plated layer on a substrate is increased by an appropriateroughness at the interface. The paper reports on plated Ni-Cu-Ag contacts forsilicon solar cells deposited into passivation layer openings that are createdusing a nano-second pulsed laser. The adhesion of plated contacts on nspulsedlaser-structured silicon ab initio is not sufficient. This is attributed toan improper surface topography. Atmospheric pressure dry etching in F_2 isintroduced as plating pre-treatment to generate a beneficial nano-roughnesson the silicon substrate. Until now, this method is used in silicon photovoltaicsonly for the formation of black silicon. Process parameters areadjusted to allow the formation of cavities in the range of 5–30 nm. Thereby,the contact adhesion increases. In peel force tests on busbars, the averagepeel-force raised from 0.3 to 2Nmm~(-1). In sheer-test on finger contacts anincrease of maximum sheer force and a decreasing length of the fingerdisplacement are observed. Due to the high etch selectivity between siliconand silicon nitride, no additional etch mask is required to protect thepassivation layer. As precursors with a non-optimized emitter design areused, the roughening procedure affects the solar cell efficiency.