Ultrafast Nonadiabatic Dynamics of Singlet Fission: Quantum Dynamics with the Multilayer Multiconfigurational Time-Dependent Hartree (ML-MCTDH) Method

Abstract

Singlet fission (SF) is supposed to potentially improve the efficiency of solar energy conversion in organic photovoltaic systems. The multilayer multiconfigurational time-dependent Hartree (ML-MCTDH) method was employed to describe the singlet fission of the pentacene system with a three-state model. The ML-MCTDH result agrees well with the previous simulations using the Redfield theory, the hierarchical equation of motion (HEOM) and the symmetrical quasi-classical (SQC) theory. We carefully investigated the role of vibrational modes with different frequencies in singlet fission dynamics. Interestingly, we observed the important contribution of a few modes with frequency resonance to electronic transition. Such a finding can be understood by revisiting the superexchange mechanism within the framework of Fermi’s golden rule. As a numerically exact method, ML-MCTDH not only provides an accurate description of the microscopy insight of the SF dynamics but also provides benchmark results to examine the performance of other approximated dynamical methods.

Charge Transport in Molecular Materials: An Assessment of Computational Methods

“…First simulations of quantum dynamics of organic systems with MCTDH were reported e.g. by Burghardt and co-workers, [366][367][368] investigating exciton dynamics and dissociation in oligothiophenes and thiophene-fullerene junctions, or by Zheng et al 369 studying singlett fission in a pentacene dimer model system. All these studies share their focus on ultra-fast processes, owing to the still present resource limitations of the method.…”

Improved on-the-Fly MCTDH Simulations with Many-Body-Potential Tensor Decomposition and Projection Diabatization

“…We conclude that the implementation of the well-known Cholesky update algorithm to solve Eqs. (11) and (14) provides an enormous saving in computation time when compared to the original method, and consequently means that calculations on much larger systems become feasible within a reasonable time; all results reported subsequently here use the Cholesky update approach.…”

Quantum Master Equation Approach to Singlet Fission Dynamics in Pentacene Linear Aggregate Models: Size Dependences of Excitonic Coupling Effects

“…Namely, in addition to the energy level matching conditions in step (i), design of intermolecular configuration (crystal packing) is found to be indispensable for describing the SF rate, which is proportional to transition probability from FE to TT state. [5,6] Another essential factor for determining the SF efficiency is involved in the exciton dynamics with vibronic couplings, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] which is the main topic in step (iii). In step (iii), various results obtained in steps (i) and (ii) are combined and are mutually correlated with the exciton dynamics caused by vibronic couplings.…”