Silver is the most expensive non-silicon
component in
photovoltaic
cells. This is particularly salient for silicon heterojunction (SHJ)
cells, which rely on large quantities of low-temperature silver pastes
(LT-SP). SHJ cells would benefit greatly from an industrially scalable
metallization process that simultaneously offers low silver consumption,
low finger resistivities (<20 μΩ·cm), and low
processing temperatures. Printed reactive silver inks (RSI) are an
innovative candidate to this end. This work furthers the research
on RSI metallization by investigating the impact of ink formula on
properties pertinent to SHJ cells, including electrical properties,
line width, ink splatter, silver consumption, cell performance, and
adhesion. We introduce a scalable, high-throughput flexible needle
contact printing approach for metallization that solves many of the
issues associated with drop-on-demand printing. The printed silver
fingers are characterized using electrical measurements and top-down
and cross-sectional microscopy. The best performing ink, consisting
of silver acetate, ethylamine, and formic acid, achieved silver fingers
with total resistivities of 3.1 μΩ·cm and contact
resistivities of 3.2 mΩ·cm2 when printed at
61 °C. This ink metallized a full-sized 156 mm × 156 mm
SHJ cell. This is the first reported data for RSI metallization of
a full-sized SHJ cell and shows how an optimized RSI can achieve similar
performances to LT-SP while consuming 80–90% less silver.
Advances in self-terminating etching processes have brought dissolvable supports to selective laser-melted stainless-steel alloys. Preliminary data showed that the amount of support material removed could be larger than the amount of material removed from the bulk material. This article details a small study aimed at understanding this phenomenon. First, the material removed and roughness as a function of applied bias is studied. From this, two different potentials were selected, 400 mV SHE , which removes 120 lm through intergranular corrosion, and 550 mV SHE , which removes material 39 lm through uniform corrosion. Next, a simulated set of support structures with wall thicknesses varying from 82 lm to 544 lm was etched under these two different potentials to report the range of thicknesses that can be reasonably removed.
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