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CuSbSe2 photovoltaic devices with 3% efficiency

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 μm thick CuSbSe$_2$ PV prototypes prepared at 380-410°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.