Optimization of laser fired contact processes in c-Si solar cells

In this work, we study the optimization of aluminium laser-fired contacts (LFC) [1] in combination with c-Si passivated solar cell [2,3]. The samples consist in p-type Fz c-Si wafers with two different passivating configurations; both thermally-grown silicon oxide (SiO2) and plasma deposited silicon carbide (SiCx) were used as the passivating rear layer. Finally, a 2μm Aluminum layer was deposited at the front and rear surface. A nanosecond Nd:YAG laser operating at 532 nm was used to fire the aluminum locally through the thin passivating layer. Green lasers offer the possibility to obtain a selective removal of the passivating layer, since the underlying silicon results typically less affected than when using IR radiation. Morphological and electrical analysis permitted to identify the optimal laser parameters to achieve good ohmic contacts and to reduce the laser-damaged area.