Improving CdSeTe Devices With a Back Buffer Layer of CuxAlOy

The open-circuit voltage (
V
_oc
) of CdTe-based photovoltaics may be limited by carrier recombination at interfaces (front or back) or in the absorber layer. Reduction in recombination of a given dominant mechanisms can lead to improved device performance if the remaining mechanisms turn
on
in a narrow bias range just below the open circuit voltage. In this article, we demonstrate enhanced performance by incorporating solution-processed Cu
_x
AlO
_y
to form a back-buffer layer in CdSe/CdTe devices. Outstanding minority carrier lifetimes of 656 and 4.2 ns were measured with glass side and film side illumination for device stacks processed with Cu
_x
AlO
_y
. Devices demonstrated efficiencies of up to 17.4% with
V
_oc
of 859 mV, FF of 75.6% and
J
_sc
of 26.9 mAcm
⁻²
while the efficiency of the reference device without the back-buffer layer was 16.5% with
V
_oc
of 839 mV, FF of 70.6%, and
J
_sc
of 27.9 mAcm
⁻²
.