First-principles ultrafast charge carrier dynamics at the hybrid F4TCNQ:H-Si(111) interface

Hybrid inorganic-organic materials are typically characterized by charge-transfer excitations across their interface that make them appealing candidates for opto-electronic applications [1]. However, the fundamental processes leading to the formation and the evolution of these states are still under debate. To address this question, we investigate from first principles the hybrid interface formed by the strong acceptor F4TCNQ adsorbed on the Si(111) surface, which is p-doped in the ground state. Its linear-absorption spectrum exhibits two maxima in the visible region corresponding to transitions between the electronic states across the inorganic and components. We investigate the dynamics of these excitations triggered by resonant ultrafast laser pulses, following the evolution of the charge-carrier population. To do so, we adopt the formalism of real-time time-dependent density-functional theory as implemented in the octopus code [2]. Our results offer insights into the earliest-stage formation of the optical excitations in hybrid interfaces.

[1] J. Sthaeler and P. Rinke, Chem. Phys. Lett. 485, 149 (2017).
[2] A. Castro, et al. Phys. Stat. Sol. B, 243, 2465,(2006).