@article{discovery1395992,
          number = {24},
         journal = {Physical Review Letters},
          volume = {107},
            year = {2011},
           title = {Nature of the band gap and origin of the conductivity of PbO2 revealed by theory and experiment.},
           month = {December},
            note = {{\copyright} 2011 American Physical Society},
          author = {Scanlon, DO and Kehoe, AB and Watson, GW and Jones, MO and David, WI and Payne, DJ and Egdell, RG and Edwards, PP and Walsh, A},
             url = {http://dx.doi.org/10.1103/PhysRevLett.107.246402},
        abstract = {Lead dioxide has been used for over a century in the lead-acid battery. Many fundamental questions concerning PbO2 remain unanswered, principally: (i) is the bulk material a metal or a semiconductor, and (ii) what is the source of the high levels of conductivity? We calculate the electronic structure and defect physics of PbO2, using a hybrid density functional, and show that it is an n-type semiconductor with a small indirect band gap of {$\sim$}0.2  eV. The origin of electron carriers in the undoped material is found to be oxygen vacancies, which forms a donor state resonant in the conduction band. A dipole-forbidden band gap combined with a large carrier induced Moss-Burstein shift results in a large effective optical band gap. The model is supported by neutron diffraction, which reveals that the oxygen sublattice is only 98.4\% occupied, thus confirming oxygen substoichiometry as the electron source.},
            issn = {0031-9007}
}