The emergence of halide double perovskites
significantly increases
the compositional space for lead-free and air-stable photovoltaic
absorbers compared to halide perovskites. Nevertheless, most halide
double perovskites exhibit oversized band gaps (>1.9 eV) or dipole-forbidden
optical transition, which are unfavorable for efficient single-junction
solar cell applications. The current device performance of halide
double perovskite is still inferior to that of lead-based halide perovskites,
such as CH3NH3PbI3 (MAPbI3). Here, by ion type inversion and anion ordering on perovskite lattice
sites, two new classes of pnictogen-based quaternary antiperovskites
with the formula of X6B2AA′ and X6BB′A2 are designed. Phase stability and
tunable band gaps in these quaternary antiperovskites are demonstrated
based on first-principles calculations. Further photovoltaic-functionality-directed
screening of these materials leads to the discovery of 5 stable compounds
(Ca6N2AsSb, Ca6N2PSb,
Sr6N2AsSb, Sr6N2PSb, and
Ca6NPSb2) with suitable direct band gaps, small
carrier effective masses and low exciton binding energies, and dipole-allowed
strong optical absorption, which are favorable properties for a photovoltaic
absorber material. The calculated theoretical maximum solar cell efficiencies
based on these five compounds are all larger than 29%, comparable
to or even higher than that of the MAPbI3 based solar cell.
Our work reveals the huge potential of quaternary antiperovskites
in the optoelectronic field and provides a new strategy to design
lead-free and air-stable perovskite-based photovoltaic absorber materials.
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