Revisiting Photoemission and Inverse Photoemission Spectra of Nickel Oxide from First Principles: Implications for Solar Energy Conversion

Abstract

We use two different ab initio quantum mechanics methods, complete active space self-consistent field theory applied to electrostatically embedded clusters and periodic many-body G0W0 calculations, to reanalyze the states formed in nickel(II) oxide upon electron addition and ionization. In agreement with interpretations of earlier measurements, we find that the valence and conduction band edges consist of oxygen and nickel states, respectively. However, contrary to conventional wisdom, we find that the oxygen states of the valence band edge are localized whereas the nickel states at the conduction band edge are delocalized. We argue that these characteristics may lead to low electron–hole recombination and relatively efficient electron transport, which, coupled with band gap engineering, could produce higher solar energy conversion efficiency compared to that of other transition-metal oxides. Both methods find a photoemission/inverse-photoemission gap of 3.6–3.9 eV, in good agreement with the experimental range, lending credence to our analysis of the electronic structure of NiO.

Structural and Electronic Features of β-Ni(OH)2 and β-NiOOH from First Principles

“…Because of this fact, and because of the numerous previous studies suggesting that the oxidation of β-Ni(OH) 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 10 functional result in excellent agreement with experiment for pure NiO. 79 Therefore, the PBE+U wavefunctions and eigenvalues of both β-Ni(OH) 2 and β-NiOOH were used as the input for the G 0 W 0 calculations. Three separate G 0 W 0 calculations were performed.…”

Promising sensitizers for dye sensitized solar cells: A comparison of Ru(II) with other earth's scarce and abundant metal polypyridine complexes

“…Polypyridyl complexes of the d 6 transition metals (Ru II , Os II , and Re I ) are mostly used in DSSCs as they have a rich photochemistry due to long‐lived metal to ligand charge transfer (MLCT) excited states . Polypyridyl complexes of these metals are widely known as DSSCs for n‐type SCs like TiO 2 . Iridium complexes are also studied for DSSCs in recent years .…”

Strategies to suppress cation vacancies in metal oxide alloys: consequences for solar energy conversion

“…The DOS shows a mixture of nickel and iron states at the conduction band edge. Furthermore, density difference plots in cluster models [40] suggest that unoccupied states of pure NiO are delocalized. We therefore expect the unoccupied states of the alloy to be at least partially delocalized, given the strong electronic coupling of Ni and Fe evident in the alloy.…”