Mixed Quantum Classical Simulations of Charge-Transfer Dynamics in a Model Light-Harvesting Complex. I. Charge-Transfer Dynamics

Abstract

We develop here a mixed quantum mechanical/ molecular dynamics model to investigate charge-transfer dynamics in a set of large organic donor−bridge−acceptor triad molecules. Specifically, we are interested in the differences in electron and nuclear behavior relating to small changes in the molecular makeup of carotenoid−porphyrin−fullerene triads. Our model approximates excitation energies on the order of 1.9 eV which agree with absorption spectra for these triads and isolated porphyrins. Using electron population analysis, we monitor charge migration to the acceptor in time. Approximations of the charge transfer rates reveal ultrafast (picosecond scale) electron dynamics consistent with experimental literature.

Photoinduced Charge Transfer Dynamics in the Carotenoid–Porphyrin–C60 Triad via the Linearized Semiclassical Nonequilibrium Fermi’s Golden Rule

“…[6][7][8][9][10][11][12][13][14][15][16][17][18] A variety of first principle computational methods for calculating photoinduced CT rates have been proposed for and applied to gas-phase molecules. [19][20][21][22][23] However, the development of similar methods for calculating photoinduced CT rates in complex condensed-phase systems remains challenging. [24][25][26][27][28] One exception is Marcus theory, which has offered an intuitive approach towards understanding CT rate constants in a wide range of condensed-phase systems, 29,30 as well as fitting and interpreting experimental measurements.…”

Direct Non-adiabatic Simulations of the Photoinduced Charge Transfer Dynamics

“…Despite the success of the current approach in simulating the model systems presented in this work, we acknowledge its potential limitations, including (i) the single-particle picture that could fail for the strongly coupled electron and hole dynamics, 22,36,37,41,72 (ii) the validity of the classical path approximation, 47,53,63,73 and (iii) the accuracy of the FSSH algorithms. 43,52 Encouraging progress is being made to address each of the above three challenges, enabling the possibility to obtain a more accurate description of the charge transfer dynamics in large complex systems.…”

“…[5][6][7] Like the natural process, there are many artificial systems in which the photoinduced charge transfer plays a crucial role. [8][9][10][11][12][13][14][15] Examples include PICT in dye-sensitized solar cells, [8][9][10][11][15][16][17] ultra-fast charge-transfer in organic photovoltaic systems, [12][13][14]18,[18][19][20][21][22][23][24][25] photocatalytic electron/hole transfer in "colloidal quantum dot-organic molecule complex" interfaces, [26][27][28] and photoinduced proton-coupled electron transfer. [29][30][31] Understanding the detailed charge transfer dynamics will provide valuable mechanistic insights and design principles for next-generation photocatalytic devices, and profoundly impact energy production and catalysis.…”

“…Our approach uses the fewest switches surface hopping algorithm 32,33 to capture the influence of nuclear vibrations on the electronic nonadiabatic transitions, and the single-particle timedependent Kohn-Sham (TDKS) approach 8,34,35 to describe the quantum mechanical state of the transferring electron. With this approach, we investigate the non-adiabatic PICT dynamics in phthalocyanine dimer/fullerene system 12,18,36 and Carotenoid-Porphyrin-C 60 (CPC) triad system, 13,19,22,23,[37][38][39] which are model systems for understanding the CT dynamics in organic photovoltaics. Our results are in excellent agreement with both experimental measurements and highlevel (yet expensive) theoretical calculations.…”

Direct Nonadiabatic Simulations of the Photoinduced Charge Transfer Dynamics

“…PICT is one of the central reactions that drives solar energy conversion in natural photosynthesis, where the charge-separated state is achieved through multiphoton absorption and involves multiple energy-conversion steps. − Like the natural process, there are many artificial systems in which the photoinduced charge transfer plays a crucial role. − Examples include PICT in dye-sensitized solar cells, − ,− ultrafast charge-transfer in organic photovoltaic systems, − ,,− photocatalytic electron/hole transfer in “colloidal quantum dot-organic molecule complex” interfaces, − and photoinduced proton-coupled electron transfer. − Understanding the detailed charge transfer dynamics will provide valuable mechanistic insights and design principles for next-generation photocatalytic devices and profoundly impact energy production and catalysis.…”