Abstract
Direct production of hydrogen from water and sunlight requires stable and abundantly available semiconductors with well positioned band edges relative to the water red-ox potentials. We have used density functional theory (DFT) calculations to investigate 300 oxides and oxynitrides in the Ruddlesden–Popper phase of the layered perovskite structure. Based on screening criteria for the stability, bandgaps and band edge positions, we suggest 20 new materials for the light harvesting photo-electrode of a one-photon water splitting device and 5 anode materials for a two-photon device with silicon as photo-cathode. In addition, we explore a simple rule relating the bandgap of the perovskite to the number of octahedra in the layered structure and the B-metal ion. Finally, the quality of the GLLB-SC potential used to obtain the bandgaps, including the derivative discontinuity, is validated against G0W0@LDA gaps for 20 previously identified oxides and oxynitrides in the cubic perovskite structure.
Highlights
A layered perovskite is composed of two-dimensional (2D) slabs of ABO3 cubic perovskite separated by a motif of metal atoms
The phase studied here is the Ruddlesden–Popper with general formula An+1BnO3n+1, where n = 1, . . . , ∞ is the number of BO6 octahedra forming the 2D slabs and the upper limit for n correspond to the cubic phase
In any case we should remark that the use of a cubic symmetry is well justified since this symmetry lowering usually disappears at high temperatures
Summary
A layered perovskite is composed of two-dimensional (2D) slabs of ABO3 cubic perovskite separated by a motif of metal atoms. There are several phases of layered perovskites which differ in the thickness and the relative displacement of the cubic perovskite slabs and in the motifs. To avoid large distortions in the octahedron, we replace the oxygen between the Aand B-atoms leaving the x y-plane of the octahedron unchanged. To investigate possible symmetry lowering in the structure (i.e. octahedra tilting and Jahn–Teller distortions). In many cases perovskites recover a cubic-like symmetry at room temperature [16, 17]
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