Light Absorption and Emission by Defects in Doped Nickel Oxide

Abstract

Nickel oxide is a versatile p‐type semiconducting oxide with many applications in optoelectronic devices, but high doping concentrations are often required to achieve necessary electrical conductivity. In contrast to many other transparent oxide semiconductors, even moderate doping levels in NiO can lead to significant optical absorption in the visible spectral range, limiting the application range of the material. This correlation has been reported extensively in the literature, but its origin has been unknown until now. This work combines experimental data on optical properties from a variety of NiO samples with results from hybrid density functional theory calculations. It shows that strong electron–phonon interaction leads to a significant blueshift (0.6–1 eV) of electronic transitions from the valence band maximum to defect states by light absorption with respect to the thermodynamic charge transition levels. This essentially renders NiO a narrow‐gap semiconductor by defect band formation already at moderate doping levels, with strong light absorption for photon energies of approximately 1 eV. The calculations are also shown to be fully consistent with experimental data on defect‐related light emission in NiO.

Photocatalytic Performance of Pristine NiO and Ni6MnO8 Nanopowders in Degradation of Rose Bengal Dye

“…The presence of these two close absorption peaks may be related to the wide size-distribution or different shapes of the synthesized nickel oxide nanoparticles. (Karsthof et al 2022) When nickel oxide nanopowder growth occurs in the presence of Mn source at different concentrations absorption peaks appeared at 318 nm and 339 nm for the sample N10M1 whereas for the sample N1M1, peaks emerged at 316 and 335 nm. The appearance of the absorption peaks suggests that the incorporation of Mn into the NiO lattice has altered the electronic structure and energy levels of the material.…”

First-Principles Study on the Role of Cu and Cl-Based Dopants in NiO

“…Previous atomistic computational models based on density functional theory (DFT) have been developed to understand how single-point defects in NiO influence bulk material properties. ,− Commonly studied intrinsic defects such as nickel and oxygen vacancies are well established in the literature. For example, the Ni vacancy is widely recognized as a shallow acceptor defect and reported as having low formation energies within NiO .…”