Electronic structure of Vanadium pentoxide: An efficient hole injector for organic electronic materials

Abstract

The electronic structure of Vanadium pentoxide (V2O5), a transition metal oxide with an exceedingly large work function of 7.0 eV, is studied via ultraviolet, inverse and x-ray photoemission spectroscopy. Very deep lying electronic states with electron affinity and ionization energy (IE) of 6.7 eV and 9.5 eV, respectively, are found. Contamination due to air exposure changes the electronic structure due to the partial reduction of vanadium to V+4 state. It is shown that V2O5 is a n-type material that can be used for efficient hole-injection into materials with an IE larger than 6 eV, such as 4,4′-Bis(N-carbazolyl)-1,1′-bipheny (CBP). The formation of an interface dipole and band bending is found to lead to a very small energy barrier between the transport levels at the V2O5/CBP interface.