  Recent technical and commercial successes of existing thin film solar cell
technologies motivates exploration of next-generation photovoltaic (PV)
absorber materials. Of particular scientific interest are compounds like
CuSbSe$_2$, which do not have the conventional tetrahedral semiconductor
bonding. Here, we demonstrate 1.5 {\mu}m thick CuSbSe$_2$ PV prototypes
prepared at 380-410{\deg}C by a self-regulated sputtering process using the
conventional substrate device architecture. The p-type CuSbSe$_2$ absorber has
a 1.1 eV optical absorption onset, ~$10^{5}$ cm$^{-1}$ absorption coefficient
at 0.3 eV above the onset, and a hole concentration of ~10$^{17}$ cm$^{-3}$.
The promising >3% energy conversion efficiency (Jsc = 20 mA/cm$^2$, FF = 0.44,
Voc = 0.35 V) in these initial devices is limited by bulk recombination that
limits photocurrent, device engineering issues that affect fill factor, and a
photovoltage deficit that likely results from the non-ideal CuSbSe2/CdS band
offset.
