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Our goal is to understand the quantum dynamics of electronic excitations in nanoscale molecular materials.
We are interested in听understanding the nature and dynamics of electronic excitations in nanoscale molecular materials, specifically organic semiconductors. These materials form the electronically active layers of established technologies, e.g. light emitting diodes in smartphones, and of emerging technologies that have not yet reached the market level including organic solar cells, organic thermoelectric devices or organic materials for quantum computing.
S. Giannini, W. -T. Peng, L. Cupellini, D. Padula, 听A. Carof, and J. Blumberger Nat. Commun. 13, 2755 (2022).听
Methodology: Our workhorse is non-adiabatic molecular dynamics simulation where the excited electronic wavefunction of the material is time-propagated on the 10 attosecond to 10 picosecond time scale by solving numerically the time-dependent electronic Schroedinger equation coupled to the nuclear motion of the atoms of the material. The electronic Hamiltonian is parametrized against first-principles electronic structure methods (typically (time-dependent) density functional theory) and the nuclear motion is treated classically. We are actively developing schemes to incorporate important nuclear quantum effects causing e.g. the decoherence of electron wavefunction to pure states.
Observables: From the time-evolution of the electronic wavefunction we calculate important transport coefficients and parameters that determine the performance of these materials in practical devices, e.g. diffusion coefficients and mobilities of excess electrons, holes or excitons and the efficiency for dissociation of excitons into free charge carriers. Apart from gaining deep fundamental insight into these processes, we aim to extract structure-function relationships and design rules that could aid the discovery of novel functional materials.
In the figure below we show our recent work on exciton diffusion in organic molecular crystals, published in Nat. Commun. 13, 2755 (2022).
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