Antiperovskite Oxides as Promising Candidates for High-Performance Ferroelectric Photovoltaics: First-Principles Investigation on Ba4As2O and Ba4Sb2O.

Owing to polarization-driven efficient charge carrier separation, ferroelectric semiconductors with narrow band gaps (∼1.3 eV) can constitute an ideal active layer for photovoltaics (PVs), as demonstrated in recent studies on lead halide perovskite solar cells. In this study, antiperovskite oxides with a composition of Ba4Pn2O (Pn = As or Sb) are proposed as promising candidates for high-performance ferroelectric PVs. Using density functional theory calculations, it is revealed that Ba4Pn2O exhibits moderate macroscopic polarization enough for charge carrier separation. Moreover, they are predicted to have direct band gaps close to the optimal Shockley-Queisser value. By investigating optical absorption coefficients and resulting short-circuit currents, it is demonstrated that a very thin layer of Ba4Pn2O can yield large photocurrents. The effective masses of charge carriers in Ba4Pn2O are found to be fairly small (<0.2me), implying facile extraction of photocarriers. The favorable simulation results along with the confirmed synthesizability of the materials strongly suggest that Ba4Pn2O will be an active layer suitable for PVs.