Ultrafast Coherent Electron–Hole Separation Dynamics in a Fullerene Derivative

Abstract

The use of fullerene derivatives as electron donors in bulk heterojunctions is a promising development in the search for efficient energy conversion in hybrid solar cells. A long-lived photoexcited electron-hole pair will give rise to increased efficiency in photoenergy conversion. One way to prevent fast electron-hole recombination is to engineer fullerene derivatives that exhibit intrinsic electron-hole separation through accessible charge-transfer excited states. In this letter, the dynamics of photoexcited electron-hole pairs in a C60 derivative is studied using the real-time time-dependent density functional theory. Although the charge-transfer excited state is not directly accessible from the ground state, intrinsic coherent electron-hole separation is observed following photoexcition as a result of direct coupling between excited states. Ultrafast charge-transfer dynamics is the dominant phenomenon in <60 fs after visible photoexcitation. This work provides insights into the characteristics of ultrafast dynamics in photoexcited fullerene derivatives, and aids in the rational design of efficient solar cells.

The Early Life of a Peptide Cation-Radical. Ground and Excited-State Trajectories of Electron-Based Peptide Dissociations During the First 330 Femtoseconds

“…Monitoring Mulliken spin densities on diagnostic atoms showed a rapid oscillation (G4 fs period) of spin density between the backbone atoms and a gradual migration of spin density to the arginine sidechain. The rapid oscillation arises from the coherence of multiple excited states, which has been seen in other work [61,62]. Ehrenfest dynamics calculations starting from the LUMO+1 state and using CAM-B3LYP/4-31G(d) gave results that were analogous but not identical to those describing the LUMO state.…”

Design and synthesis of indole-substituted fullerene derivatives with different side groups for organic photovoltaic devices

“…One can see that the LUMO levels of the fullerene derivatives mainly locate on the C60, and the HOMO mainly on the indole units. This phenomenon was consistent with the reported results [49,50]. The theoretical energy level values are summarized in Table 2.…”

Theoretical estimation of the rate of photoinduced charge transfer reactions in triphenylamine C60 donor–acceptor conjugate

“…There are some experimental and theoretical works wherein real-time dynamics of CS states in fullerene DSSCs were described. [85,86] For our purposes we highlight the study carried out by Li et al [87,88] where simulations based on real-time dynamics were performed for a C60 fragment (the acceptor) covalently linked to an aniline derivative (the donor). Regardless the oscillator strength, they show the population of LUMO, depopulation of HOMO and population/depopulation of HOMO-1 (coincidently, those MOs resemble the ones in Fig.…”