Non-negligible roles of charge transfer excitons in ultrafast excitation energy transfer dynamics of a double-walled carbon nanotube

Abstract

Herein, we employed a developed LR-TDDFT-based nonadiabatic dynamics simulation method that explicitly takes into account the excitonic effects to investigate photoinduced excitation energy transfer dynamics of a double-walled CNT model with different excitation energies. The low E11 excitation of the outer CNT that generates a locally excited (LE) |out*⟩ exciton does not induce any charge separation. In contrast, the E11 excitation of the inner CNT can generate four kinds of excitons with the LE exciton |out*⟩ dominates. In the 500-fs dynamics simulation, the LE exciton |in*⟩, charge transfer (CT) excitons |out-in+⟩ and |out+in-⟩ excitons are all gradually converted to the |out*⟩ exciton, corresponding to a photoinduced excitation energy transfer, which is consistent with experimental studies. Finally, when the excitation energy is close to the E22 state of the outer CNT (~1.05 eV), a mixed population of different excitons, with the |out*⟩ exciton dominated, is generated. Then, the photoinduced energy transfer from the outer to inner CNTs occurs in the first 50 fs, which is followed by an inner-to-outer excitation energy transfer completed in 400 fs. The present work not only sheds important light on the mechanistic details of wavelength-dependent excitation energy transfer of a DWCNT model, but also demonstrates the roles and importance of the CT excitons in photoinduced excitation energy transfer. On the other hand, it also emphasized that explicitly including the excitonic effects in electronic structure calculations and nonadiabatic dynamics simulations is significant for either correct understanding or rational design of optoelectronic properties of periodically extended systems.

Nonadiabatic Dynamics Simulations for Photoinduced Processes in Molecules and Semiconductors: Methodologies and Applications

“…Recently, we extended the LR-TDDFT-based NAMD simulation method, which is mainly used for investigating molecular systems, to semiconductor materials as well to incorporate the excitonic effects in periodic systems. 116 The developed method was used to evaluate the photoinduced excitation energy transfer dynamics of a doublewalled CNT (DWCNT) model composed of SWCNT(11,0) (inner CNT) and SWCNT(20,0) (outer CNT) with different excitation energies. Our simulation results indicated that the DWCNT may exhibit different exciton dynamics upon excitation with different energies and the CT and dark excitons are expected to play important roles during the whole process (Figure 14).…”

“…Lu et al combined the LR-TDDFT method with NAMD method to investigate the excitonic effects on the ultrafast charge separation and energy transfer process in TMD heterojunctions. , It is worth emphasizing that in order to reduce the computational effort associated with the Fock-like exchange on large systems, they applied first order perturbation theory to the range-separated hybrid Kohn–Sham Hamiltonian and obtained the first-order corrected eigenvalues and eigenfunctions. Recently, we extended the LR-TDDFT-based NAMD simulation method, which is mainly used for investigating molecular systems, to semiconductor materials as well to incorporate the excitonic effects in periodic systems . The developed method was used to evaluate the photoinduced excitation energy transfer dynamics of a double-walled CNT (DWCNT) model composed of SWCNT­(11,0) (inner CNT) and SWCNT­(20,0) (outer CNT) with different excitation energies.…”

“…Proposed mechanisms of the photoinduced exciton dynamics in DWCNT­(11,0)@(20,0) upon excitation with different energies based on NAMD simulations, in which excitonic effects are explicitly considered. Adapted with permission from ref . Copyright 2023 AIP Publishing.…”

Vitality of Intralayer Vibration in hBN for Effective Long-Range Interlayer Hole Transfer across High Barriers in MoSe2/hBN/WSe2 Heterostructures

“…Aiming to explore detailed interlayer hole transfer processes from the MoSe 2 to the WSe 2 upon the photoexcitation, a set of NAMD simulations accompanied with the “neglect of back-reaction” approximation (also known as the “classical path approximation”), powerful tools for revealing ultrafast dynamics of the photoreaction, , charge transfer, − charge recombination, and charge transport − upon photoexcitation in molecular and periodic systems, are conducted for H 0L , H 1L , H 2L , and H 3L configurations at a temperature of 100 K (denoted as H 0L -100K, H 1L -100K, H 2L -100K, and H 3L -100K, respectively). Besides, the temperature effect has been examined by performing another simulation for H 3L at a temperature of 300 K (H 3L -300K) (Figure ) (details are listed in Supporting Information).…”

“…This approach is based on the following three considerations. First, the inclusion of the excitonic effect requires the GW Bethe–Salpeter equation (GW-BSE) or the time-dependent DFT (TDDFT) ,, to describe the many-body effect, requiring too expensive and unaffordable computation resources for NAMD simulations. Second, previous investigations have proved that NAMD simulations within the DFT framework could provide useful results for the type-II heterostructures where only the electron transfer or the hole transfer is considered the major process upon the photoexcitation .…”