In this work, we have investigated Cu 2 SiSe 3 as a candidate photovoltaic absorber, determining its bandgap to be 1.52 eV using HSE06. A maximum efficiency of 30% at the radiative limit is predicted for thin film devices, and we expect current copper-chalcogenide device architectures to be readily transferable. Using hybrid density functional theory, all intrinsic defect sites were investigated, with the lowest energy defects (V Cu and Cu i ) expected to be benign with respect to carrier recombination. As a result, Cu 2 SiSe 3 shows great promise as a potential defect-tolerant photovoltaic absorber, however further calculations of capture crosssections are required. We believe this work serves as a promising outlook on the potential solar cell application of this material, and hope that it encourages experimentalists working in the field of emerging photovoltaics to synthesize and investigate Cu 2 SiSe 3 devices.