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

Abstract

Fullerene based molecular heterojunctions such as the [6,6]-pyrrolidine-C60 donor-acceptor conjugate containing triphenylamine (TPA) are potential materials for high-efficient dye-sensitized solar cells. In this work, we estimate the rate constants for the photoinduced charge separation and charge recombination processes in TPA-C60 using the unrestricted and time-dependent DFT methods. Different schemes are applied to evaluate excited state properties and electron transfer parameters (reorganization energies, electronic couplings, and Gibbs energies). The use of open-shell singlet or triplet states, several density functionals and continuum solvation models is discussed. Strengths and limitations of the computational approaches are highlighted. The present benchmark study provides an overview of the expected performance of DFT-based methodologies in the description of photoinduced charge transfer reactions in fullerene heterojunctions.2

The Driving Force of Photoinduced Charge Separation in Metal‐Cluster‐Encapsulated Triphenylamine‐[80]fullerenes

“…Then, LE 1 and CS 1 are found at 1.64 and 1.54 eV above the ground state. These estimates are in good agreement with the experimental energies of 1.50 and 1.45 eV, respectively . LE 1 and CS 1 levels in the solvated complexes are depicted in Figure .…”

“…Changes in electronic energy, Δ E ct , for CT reactions are assumed to be nearly equal to changes in Gibbs energy, Δ G ct , (the entropic term for all compounds is expected to be very similar). In a previous study, we noted that the relaxed geometry of a charged state, D + ‐A − , does not involve significant geometrical changes as compared to the equilibrium geometry of the ground state …”

“…In ap reviouss tudy,w en oted that the relaxed geometry of ac harged state, D + -A À ,d oes not involve significant geometricalc hangesa sc ompared to the equilibrium geometry of the ground state. [79]…”

“…These estimates are in good agreement with the experimental energies of 1.50 and 1.45 eV,r espectively. [36,79] LE 1 and CS 1 levelsi nt he solvated complexes are depictedi nF igure 3.…”

Charge-Separation and Charge-Recombination Rate Constants in a Donor–Acceptor Buckybowl-Based Supramolecular Complex: Multistate and Solvent Effects

“… 40 Nonetheless, this state-specific PCM method has been barely employed in charge-transfer contexts. 41 In addition to continuum models, polarizable force fields explicitly including solvent molecules surrounding the supramolecular complexes have been employed to describe CT excited states in solution. 42 …”