Nature of the Band Gap and Origin of the Conductivity ofPbO2Revealed by Theory and Experiment

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 ∼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.

The electronic structure of the antimony chalcogenide series: Prospects for optoelectronic applications

“…This can reduce the band gap and has become an important concept in band gap engineering and is used to design devices with tailored band gaps for optoelectronic applications [72,73,74,75]. Additionally, the valence band mixing of metal s with anion p states suggests that materials with lone pairs on the cations may be good candidates for p-type conducting materials [76,77,78,79]. As the Sb III cations are expected to posses lone pairs for the distorted systems, this may indicate that they could be potental candidates for p-type conducting materials.…”

Growth and properties of GaSbBi alloys

“…[15][16][17] Here, the screened Heyd-ScuseriaErnzerhof (HSE) hybrid density functional is used, 18 as implemented in the VASP code. 19 The value of exact nonlocal exchange, a, was 32.5%, which yields a band gap of 841 meV for GaSb, in good agreement with the 0 K band gap of 812 meV extrapolated from low temperature experimental data.…”

Исследование Механических, Электронных И Колебательных Свойств Оксидов Свинца Из Первых Принципов

“…Пространственная группа β-PbO 2 P4 2 /mnm, Z = 2, a = 4.9556 ¦ , c = 3.3867 ¦ [39]. С по-мощью градиентного PBE и гибридного HSE06 функци-оналов параметры кристаллической структуры β-PbO 2 рассчитаны в [43].…”

“…Электронная структура диоксида свинца c исполь-зованием градиентного (PBE) и гибридного (HSE06) функционалов плотности детально исследована в [43], и показано, что он является полупроводником n-типа с узкой непрямой запрещенной зоной 0.23 eV при экс-периментальном значении 0.61 eV [72]. Ширина прямой запрещенной щели равна −0.70 eV для расчета с исполь-зованием функционала PBE и 0.35 eV -для HSE06.…”