p-Type Conductivity of Hydrated Amorphous V2O5 and Its Enhanced Photocatalytic Performance in ZnO/V2O5/rGO

Vanadium pentoxide (V2O5) is known to have natural n-type conductivity but transitions from n- to p-type conductivity when grown in a hydrated amorphous phase via atomic layer deposition. Compared with the intrinsic n-type character of V2O5, the hydrated amorphous V2O5 with artificial p-type conductivity has an increased work function difference, which can build stronger interface electric fields in ZnO/V2O5 heterojunction structures. This increased internal electric field strengthens the electron–hole separation across the heterojunction interface, which in turn improves the photocatalytic and photoelectrochemical performance of the structure. Using first-principles calculations, we found that when H2O molecules are incorporated into the amorphous V2O5 matrix, delocalized empty states are freshly formed above the valence band maximum in the hydrated amorphous V2O5, playing a crucial role in the transition of electrical conductivity within V2O5. This approach provides a simple and efficient way to discover new p-type materials and apply them to future p–n junction devices in terms of process simplicity and cost effectiveness.