State-of-the-Art CuInSe2, Cu(In,Ga)Se2
and Modified-CuGaSe2 Solar Cells
Jehad AbuShama
National Renewable Energy Laboratory
Golden, CO 80401
Abstract
CuIn1-xGaxSe2 (CIGS) (0 = x = 1) thin-film solar cells have great
potential
for photovoltaic applications. The energy bandgap for this material
varies
from ~1.0 eV for CIS to ~1.7 eV for CGS. Recently, our group at NREL
demonstrated new world-record NREL-confirmed total-area efficiencies of
15%, 19.5%, and 10.2% for CIS, CIGS (x~0.3), and modified-CGS solar
cells,
respectively. The improved device efficiencies resulted from modified
growth processes of the absorber layers. For example, we attempted to
modify the surface region of the CGS absorber to be CIGS-like in
composition. I will present a comparison between the different material
and
device properties for the state-of-the-art thin-films and devices. For
example, I will discuss the role of grain boundaries on device
performance,
and differences in point defects. At the end, I will present an update
on
tandem solar cells. Recently, our group at NREL demonstrated new record
NREL-confirmed efficiencies of 9.7% and 15.3% for mechanical-stacked
CGS/CIS and CdTe/CIS tandem cells, respectively.