Ultrafast charge transfer and vibronic coupling in a laser-excited hybrid inorganic/organic interface

Abstract

Hybrid interfaces formed by inorganic semiconductors and organic molecules are intriguing materials for opto-electronics. Interfacial charge transfer is primarily responsible for their peculiar electronic structure and optical response. Hence, it is essential to gain insight into this fundamental process also beyond the static picture. Ab initio methods based on real-time time-dependent density-functional theory coupled to the Ehrenfest molecular dynamics scheme are ideally suited for this problem. We investigate a laser-excited hybrid inorganic/organic interface formed by the electron acceptor molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4TCNQ) physisorbed on a hydrogenated silicon cluster, and we discuss the fundamental mechanisms of charge transfer in the ultrashort time window following the impulsive excitation. The considered interface is p-doped and exhibits charge transfer in the ground state. When it is excited by a resonant laser pulse, the charge transfer across the interface is additionally increased, but contrary to previous observations in allorganic donor/acceptor complexes, it is not further promoted by vibronic coupling. In the considered time window of 100 fs, the molecular vibrations are coupled to the electron dynamics and enhance intramolecular charge transfer. Our results highlight the complexity of the physics involved and demonstrate the ability of the adopted formalism to achieve a comprehensive understanding of ultrafast charge transfer in hybrid materials.

Formation of Lead Halide Perovskite Precursors in Solution: Insight from Electronic‐Structure Theory

“…To do so, we make use of the Bader scheme, [61][62][63][64] which enables a flexible partition of the charge density among different spatial domains. This method, based on the partition of the electron density computed from DFT is particularly useful in (hybrid) materials and interfaces formed by heterogeneous building blocks, [65][66][67][68][69] and it is known to be more reliable than the Mulliken or the Hirshfeld schemes in the presence of noncovalent bonds. [70] With the aim to understand the nature of the chemical bonds within the LH backbones as well as between them and the solvent molecules, we consider two types of partitions.…”

Quantum Nuclei at Weakly Bonded Interfaces: The Case of Cyclohexane on Rh(111)

“…See the discussion in the Section S4, Supporting Information, regarding the inclusion of different vibrational modes in this ZPE correction. The quasi-harmonic (QH) ZPE-corrected energy of adsorption E * ads was then calculated according to Equation (7). These values were calculated with the PBE+vdW surf functional, because it delivers a good description of the desorption curve, and its computational cost and implementation in the FHI-aims code allow a fast computation of thousands of force evaluations-which is not the case for the other functionals we show here.…”

“…Modeling these effects becomes more important as the field moves toward soft and hybrid electronic materials, where electronphonon coupling tends to be more pronounced. [6,7] A common way to address such problems is to employ the harmonic approximation for the nuclear vibrations on first-principles potential energy surfaces. [8] However, the validity of this approximation in weakly bonded systems and interfaces, where anharmonic terms in the potential energy surface are expected to play a role, is questionable.…”

“…Shaded areas show the interval of reported experimental values of the adsorption energy of C 6 H 12 (red) and C 6 D 12 (grey) around the coverages we study [2]. b) ZPE-corrected energy of adsorption for C 6 H 12 (red) and C 6 D 12 (black), calculated according to Equation(7) with PBE + vdW surf . Blue line shows the adsorption energy values calculated without ZPE correction.…”

Laser-Controlled Charge Transfer in a Two-Dimensional Organic/Inorganic Optical Coherent Nanojunction

“…3 Depending on the physico-chemical properties of the constituents and on the nature of their mutual interactions, in these systems, charge transfer can be achieved already in the ground state, [4][5][6][7] or it can be triggered in the excited state by the action of a laser. [8][9][10] The choice of transition-metal dichalcogenide (TMDC) monolayers as inorganic substrates for hybrid interfaces is particularly advantageous, due to the band-gap size of these materials, 11,12 their large carrier mobility, 13,14 as well as their extraordinary light-matter couplings 15,16 even in the ultrafast regime. [17][18][19][20] Decorating these systems with organic molecules has opened additional pathways to tune their properties.…”