Conducting Behavior of Crystalline α-PbO2 as Revealed by DFT Calculations

Abstract

PbO 2 is one material that has recently emerged as potential transparent conducting oxide for applications in the modern opto-electronic industry. In this work the electronic structure of the α-PbO 2 polymorph has been investigated, aiming to contribute to the understanding of its high levels of conductivity. DFT calculations using B3LYP hybrid density functional and considering long range interactions among the atoms have been performed. A direct band gap of 0.90 eV has been found, compatible with high conductivity values. Although the stoichiometric material is somewhat transparent, the band structure indicates that appropriated modifications in the material Fermi level can be performed in order to decrease the absorption of light. Charge distribution plus overlap population analysis show that the material is predominantly ionic. The charge distribution throughout the material is strongly dependent on the crystal direction. Results suggest that α-PbO 2 can be potentially more interesting for opto-electronic purposes than the β polymorph.

Grain Boundaries in Methylammonium Lead Halide Perovskites Facilitate Water Diffusion

“…We discuss next the details of water diffusion in MAPbI which is larger than that in other Pb─O covalent compounds (e.g., the Pb─O bond lengths are 2.12-2.44 Å in α-PbO 2 ). [55] Thus, we infer that the Pb-O covalent interaction is quite weak and its breaking during the diffusion is not a dominant contributor for the diffusion barrier. The loose atomic structure along paths 1 and 2 is responsible for their small E b , see the transition states in Figure 3.…”

Computational procedure to an accurate DFT simulation to solid state systems

“…An appropriate choice can lead to accurate target properties being simulated reliably, especially when dealing with models for which there are no experimental information for comparison. 9 In particular, hybrid functional has been employed with success to simulate solid-state systems, such as the study of the bulk, 10,11 surfaces, 12 nanotubes 13 , adsorption, and doping processes. 14 As a popular example, the B3LYP [15][16][17] hybrid functional is a common choice to describe the properties of several systems.…”