Thermoradiative cells (TRCs) are power generators that efficiently convert low temperature waste heat into electricity. Although there is a growing interest in this potential technology, most of the works dealing with the study of efficient TRCs are focused on the theoretical analysis of their performance. In this work, a Cu3SbSe4 semiconductor is proposed to be applied in TRCs. Firstly, the electronic structure of Cu3SbSe4 has been obtained by using density functional theory (DFT) calculations. Then, DFT calculated bandgap values are employed to assess the efficiency of TRCs based on Cu3SbSe4. For this purpose, the power conversion efficiency has been calculated by using the Shockley–Queisser framework through a detailed balance model adapted to TRCs that includes the doping level through its effect on the energy barrier appearing at the pn-junction.