Ab initio charge carrier dynamics and its application to materials for energy

Abstract

This talk will discuss novel first-principles calcns. of charge carrier dynamics, which are broadly applicable to materials employed in renewable energy devices. Calcns. of charge transport and ultrafast dynamics have relied on heuristic approaches for the past several decades. Recent progress in combining d. functional theory and related methods with kinetic equations, such as the Boltzmann transport equation (BTE), are enabling spectacular advances in computing carrier dynamics in materials from first principles. A special role is played by the interaction between charge carriers and lattice vibrations, also known as the electron-phonon (e-ph) interaction, which dominates carrier dynamics near room temp. and at energies within a few eV of the band gap. We will discuss our recently developed methods to compute e-ph scattering processes from first principles, and show how these developments enable accurate calcns. of charge transport and ultrafast dynamics in materials, including: 1) Accurate calcns. of the electron mobility, leading to new insight into charge transport in polar semiconductors, perovskite oxides, and org. materials. We will also touch briefly on the computation of charge transport in the polaron regime. 2) The ultrafast dynamics of excited (so-called "hot") carriers, with application to lighting devices, solar energy conversion, and ultrafast spectroscopy. A new parallel algorithm to propagate in time the BTE for excited electrons and coupled electrons and phonons will be presented. A recent extension to include the elec. field in the BTE and accurately compute velocity-field curves in semiconductors will also be discussed. The talk will close with a discussion of PERTURBO, an open source code we are developing to make these calcns. available to the community.