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 transport layer and fabricated a BaCoF4/Cs0.05MA0.14FA0.81PbI2.55Br0.45-based solar cell device. Notably, the solar cell devices yield the champion power conversion efficiency of ca. 13.14%. We also investigate photovoltaic properties of other analogous materials and find that BaNiBr4 and BaMnCl4 also possess both multiferroic and photovoltaic bifunctionalities. Hence, this new class of BaMX4 offers diverse and tunable capability for various applications.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films