A New Class of Bifunctional Perovskites BaMX4 (M = Co, Ni, Fe, Mn; X = F, Cl, Br, I): An n-Type Semiconductor with Combined Multiferroic and Photovoltaic Properties

Abstract

We design a new class of bifunctional materials, namely, BaMX4 (M = Co, Ni, Fe, Mn; X = F, Cl, Br, I), with corner-shared octahedral layered perovskite structures. Our joint experimental and theoretical study demonstrates that BaCoF4, a prototype in this new class, possesses a unique combination of multiferroic and photovoltaic properties. Moreover, BaCoF4 exhibits both an antiferromagnetic spin structure and ferroelectric polarization along the (001) direction. These combined electronic and optical features render BaCoF4 a promising bifunctional material for application in spintronic or photovoltaic devices. Density functional theory calculations suggest that the dominant point defects in BaCoF4 are mostly shallow-level donor defects, leading to fascinating n-type self-doping. As such, a BaCoF4 layer may be exploited for electron transport and light absorption altogether, which may enhance the photovoltaic performance in solar cells. To confirm this predicted feature, we incorporate BaCoF4 as an electron...