A collaborative effort between
NREL's Amorphous Silicon Team and United Solar Systems
Corporation (Uni-Solar) has produced an efficient
midgap solar cell whose active layer—a-SiGe:H
alloy—is deposited at the high rate of 10 Å/s
using the hot-wire chemical vapor deposition (CVD)
technique. A power of 4.2 mW/cm2 was measured through
a 530-nm cutoff filter, which means that this cell
would contribute about 4.2% as the midgap middle cell
in a 12%- to 14%-efficient triple cell. Uni-Solar's
best 6 Å/s midgap cell delivers 4.4 mW/cm2 .
This new result shows the potential of fabricating
high-efficiency tandem or triple-junction amorphous
silicon solar cells at higher deposition rates, an
important result for low-cost production of PV modules.
The delivered power of 4.22 mW/cm2 is an active-area
measurement, with a short-circuit current density
(Jsc) of 8.05 mA/cm2 after correction by quantum efficiency
measurement. The fill factor (FF) is 0.69 and the
open-circuit voltage (Voc) is 0.76 V. Light soaking
of this cell to determine its stabilized efficiency
is under way.
Application
Production of Photovoltaics modules
and high-efficiency tandem or triple-junction amorphous
silicon solar cells.
