First-principles study of R3c-MgSnX3 (XO, S and Se) for photovoltaic and ferroelectric application

•R3c-MgSnX3 (XO, S and Se) are metastable structure by phonon frequencies analysis.•R3c-MgSnX3 (S and Se) holds high ferroelectric polarization and reduces the bandgap.•MgSnS3 has high photovoltaic efficiency with large ferroelectric polarization. Polarized structure oxides have unique advantages in photovoltaic field with internal electric field, but it is difficult to make full use of them with visible light in general due to their large band gap. The stability and electronic structure properties of a novel R3c polarization structure MgSnX3 (XO, S and Se) have been calculated by first-principles method. The calculated results show that the elastic coefficients and phonon frequencies of R3c-MgSnX3 (XO, S and Se) satisfy the mechanical stability conditions. R3c-MgSnX3 (S and Se) maintains a higher theoretical ferroelectric polarization strength than R3c-MgSnO3, and at the same time reduces the band gap obviously. Spectroscopic Limited Maximum Efficiency calculation also shows that MgSnS3 has high photoelectric conversion efficiency and is a potential ferroelectric photovoltaic material with high efficiency.