A review on the optical characterization of V2O5 micro-nanostructures

Bulk V2O5 is a diamagnetic semiconductor with a band gap (E-g) of about 2.3 eV, which is based on the ionic configuration with filled O2p and unoccupied V3d orbitals. However, the band edge absorption and photoluminescence (PL) peak positions of low-dimensional V2O5 materials do not coincide and are distributed over wide ranges of 0.75-3.49 eV and 0.73-3.3 eV, respectively. This review summarizes the fabrication processes, structure, and optical characterization of V2O5 micro-nanostructures, including OD, 1D, 2D, and 3D morphologies. The wide ranges of band edge absorption and broad PL of V2O5 micro-nanostructures are clarified in terms of factors such as the morphology, synthesis method, growth conditions, crystal size, micro-nano size, phase transition, and measurement conditions. The relations among the separation, diffusion, recombination, and degradation of the electron-hole pairs in V2O5 micro-nanostructures are also discussed. Fundamental understanding of the optical characteristics plays a key role in V2O5 micro-nano device applications. The review also demonstrates the role of V2O5 micro-nanostructures and other materials (MOs) in V2O5/OMs heterostructures for slowing down recombination, prolonging lifetime, improving electron-hole separation, and increasing photocurrent to enhance the photocatalytic activity.