Antiperovskite Sr3MN and Ba3MN (M = Sb or Bi) as promising photovoltaic absorbers for thin-film solar cells: A first-principles study

Although lead halide perovskites (LHPs) have emerged as interesting photovoltaic (PV) absorbers for thin-film solar cells, the toxicity of Pb and poor materials stability have hindered the commercialization of solar cells using LHPs. Herein, using density functional theory (DFT) calculations, we suggest antiperovskite nitrides Sr₃MN and Ba₃MN (M = Sb or Bi) as potential Pb-free PV absorbers for thin-film solar cells. State-of-the-art DFT calculations based on the GW approximation show that these compounds have direct bandgaps suitable for PV applications. In addition, they exhibit significant absorption coefficients over 10⁵ cm^?1 for the visible light. By calculating spectroscopic limited maximum efficiency, we demonstrate that the film thicknesses of several hundred nanometers are enough for Sr₃MN and Ba₃MN to generate high-power conversion efficiencies over 20%. The analysis of the electron and hole effective masses reveals that these compounds have efficient carrier-diffusion paths allowing for the facile extraction of photocarriers. Lastly, we investigate the band alignments of the materials to help the design of thin-film solar cells.