Similar to other P-rich phosphides, bulk synthesis of CuP 2 as a single-crystal or powder is well established but there are no reports of thin-film growth. CuP 2 is a semiconductor that has been proposed as a solar absorber, thermoelectric material, electrocatalyst for hydrogen-and oxygen evolution, and as a component in composite anode materials for Li- and Na-based batteries. Although CuP 2 has been incorporated in electrochemical devices, its optoelectronic and thermoelectric characterization is incomplete. For example, the optical absorption coefficient of CuP 2 crystals has only been measured in the weak absorption region just above its 1.4 eV-1.5 eV band gap, 8,10 so it is impossible to evaluate its performance as a light absorber in the visible. For thermoelectric applications, the properties needed to calculate the quality factor zT have only been measured separately on different CuP 2 specimens in singlecrystal or powder form. A potential method for growing phosphorus-rich phosphide thin films is reactive sputtering. We have recently shown the feasibility of this deposition technique for various metal-rich phosphide compounds. In this work, we demonstrate a relatively simple two-step process route to grow polycrystalline CuP 2 thin films as semiconductors of potential technological interest. First, reactive sputter deposition of amorphous CuP 2+x in a PH 3 -containing atmosphere; second, crystallization by rapid thermal annealing (RTA) in an inert atmosphere. We find that the crystallization step must be kinetically facilitated by employing amorphous precursors of sufficiently similar composition to the desired CuP 2 stoichiometry. We investigate the optical properties of CuP 2 over a broad spectral range and conduct comprehensive temperaturedependent thermoelectric characterization (including the zT value) up to room temperature. In particular, we find a remarkably high optical absorption coefficient (above 10 5 cm -1 in the visible), low thermal conductivity (1.1 W/Km), composition-insensitive electrical conductivity (1 S/cm) and a moderate native doping density (10 15 cm -3 -10 17 cm -3 ) potentially suitable for photovoltaic applications.