Real-Time Atomistic Dynamics of Energy Flow in an STM Setup: Revealing the Mechanism of Current-Induced Molecular Emission

Abstract

Detailed understanding of the current-induced fluorescence mechanism constitutes an exciting challenge as it can open the way to efficient coupling between an electric field and light at the nanoscale. At the same time, a number of published experimental studies give an unclear, contradictory picture of this phenomenon working principle. Here, for a system consisting of a silver tip and a porphyrin molecule, we perform for the first time fully atomistic, real-time nonadiabatic dynamics simulations to study the process of energy transfer and relaxation in an STM setup. We calculate time scales of all crucial processes and explain their atomic details. On this basis, we confirm and characterize the dual mechanism of the observed emission based on competing elastic and inelastic electron transfer between the metal tip and the molecule.

Long Carrier Lifetimes in PbI2-Rich Perovskites Rationalized by Ab Initio Nonadiabatic Molecular Dynamics

“…Compared with many other photocatalytic materials, − both MAI-rich and PbI 2 -rich perovskites exhibit long, nanosecond recombination times, matching well the previous experimental ,, and theoretical ,,− ,, reports. Further, we calculated the radiative lifetimes using the Einstein coefficient for spontaneous emission and obtained 63.1 and 31.7 μs for the MAI-rich and PbI 2 -rich perovskites, respectively, in agreement with the previous experimental and theoretical reports. ,− The radiative lifetime is several orders of magnitude longer than the nonradiative lifetime, indicating that nonradiative relaxation constitutes the main mechanism of charge recombination. Such long nonradiative and radiative recombination times result in large electron and hole diffusion lengths observed in the perovskite materials.…”

Electron–Phonon Scattering Is Much Weaker in Carbon Nanotubes than in Graphene Nanoribbons

“…A detailed description of the simulation methodology can be found in ref and , which are based on earlier work. , The approach has been used successfully over a broad range of systems, − showing good agreement with corresponding experiments and providing a detailed atomistic description of complex quantum dynamics in nanoscale materials.…”

MAI Termination Favors Efficient Hole Extraction and Slow Charge Recombination at the MAPbI3/CuSCN Heterojunction

“…The quantum decoherence correction to FSSH is used in the electron–hole recombination simulation, − because the recombination time is much longer than the decoherence time. The decoherence time is computed by the second-order cumulant approximation of the optical response theory. , The approach has been applied successfully to study photoexcitation dynamics in a broad range of systems, including perovskites − and many other materials. − A detailed description of the theoretical methodology can be found in refs and .…”