Evidencing Prominent Involvement of Bi Orbitals of BiFeO₃ in Eliciting Charge-Transfer Excitation

However, the performance of BFO depends on its electronic properties and charge-transfer (CT) excitation, which are governed by the extent/choice of orbitals involved in hybridization. The CT excitation is often assumed to occur due to electron transitions from the O 2p to Fe 3d orbitals of the conduction band (CB), while completely disregarding the role of Bi 6p orbitals.

For the first time, using near-ambient x-ray photoelectron spectroscopy under light illumination, valence states of BFO constituents are deconvoluted. By selectively probing different orbitals of the CB under illumination, the often-ignored role of Bi orbitals in CT excitation is rationalized. In addition, ultrafast transient absorption spectroscopy unravels the distinctive decay behavior of charge carriers in CB states compared with that in in-gap defects.