Abstract:
Photovoltaic solar cells offer many
advantages, including needing little maintenance,
environmentally benign of any electricity generating source
with zero greenhouse gas emission. In the photovoltaic
industry both the reduction of the silicon material thickness
and the increase of the solar cells efficiency are critical
topics for cost reduction. One key factor to reducing the
cost and energy consumption of solar cell production
process is reducing the thickness of the Si wafer to the order
of 200 μm, the current industry wafer thickness ranges of
275 - 350 μm. The back-surface field (BSF), ~50 μm thick is
formed during the firing of a screen printed A1 on the rear
side. The main issue using thinner wafers with Al BSF is the
bow of the wafers after firing.
In this study, baseline Si Solar cells with 19.7% light
conversion efficiencies was achieved on monocrystalline ptype
CZ-Si with two types of Al BSF pastes. High
performance SiN:H was grown by PECVD tool. The Al/Ag
firing process for the Sun Chemical product (CTX 0435)
needs to be optimized as the current process disintegrates
to powder substance after Ag firing. The process window
for firing the DuPont Ag front-side paste is large and yields
low series resistance values without forming gas anneal
(FGA anneal).
