Quantum Interference in Singlet Fission: J- and H-Aggregate Behavior

Abstract

The quantum interference in singlet fission (SF) among the multiple pathways from singlet excited states to correlated triplet pair states is comprehensively investigated. The analytical analysis reveals that this interference is strongly affected by the exciton-exciton coupling and is closely related to the property of J- and H-type of aggregates. Different from the interference in the spectra of aggregates, which depends only on the sign of exciton-exciton coupling, the interference in SF is additionally related to the signs of couplings between singlet excited states and triplet pair states. The interference dynamics is further demonstrated numerically by a time-dependent wavepacket diffusion method with electron-phonon interactions incorporated. Finally, we take a pentacene dimer as a concrete example to show how to adjust the constructive and destructive interferences in SF dynamics in terms of J-/H-aggregate behaviors. The results presented here may provide guiding principles for designing efficient SF materials through directly tuning quantum interference via morphology engineering.

The hierarchical and perturbative forms of stochastic Schrödinger equations and their applications to carrier dynamics in organic materials

“…By changing the signs of the five couplings V ex , V LL , V HH , V LH and V HL , various different quantum interference effects may appear. However, it has been shown that the results can be sorted into several different groups. Under the assumption that the energies of the two CT states are much higher than other states, the Hamiltonian Equation 45 can be simplified as an effective three‐levels Hamiltonian via a partitioning technique: where the effective energies are …”

“…(d) the SF rates in terms of V ex in dimer (solid line) and 10 monomer (dashed line) models. (Reprinted with permission from Reference . Copyright 2017 American Chemical Society)…”

Combined molecular and periodic DFT analysis of the adsorption of co macrocycles on graphene

“…[1,4,5] Due to the absence of band gap around the Fermi level, numerous approaches have been developed using molecular doping to tailor the transport properties of graphene-based devices for nano-electronic and photonic applications. [6][7][8][9][10][11][12][13][14] More generally the chemical functionalization of graphene is crucial for a variety of technological applications including novel electronics [10,12,[15][16][17][18] or spintronic devices, [19][20][21] photodetectors, [22,23] catalysis, [24] molecular sensors, [25][26][27][28][29] fieldeffect transistors, [13,17,29] new energy materials, [18,30,31] or novel hybrid species with original properties. [32][33][34][35][36][37][38] In this context, the noncovalent functionalization based on p -p stacking is usually preferred to covalent treatments which may degrade the aromaticity of the carbon surface by creating sp 3 carbon defects, thus, lowering the high carrier mobility.…”

“…[32][33][34][35][36][37][38] In this context, the noncovalent functionalization based on p -p stacking is usually preferred to covalent treatments which may degrade the aromaticity of the carbon surface by creating sp 3 carbon defects, thus, lowering the high carrier mobility. [6,12,32,[39][40][41][42] Among the various experimental or theoretical studies published on aromatic molecules for graphene p-doping, two main families emerge. The most studied doping molecules have been tetracyanoquinodimethane (TCNQ) or tetracyanoethylene (TCNE) and tetrathiafulvalene (TTF).…”

“…[6,7,10,32,[42][43][44][45][46][47][48][49][50][51] The former molecules or their fluorine derivatives have been shown to promote p-doping of graphene due to their wellknown acceptor character while TTF favors a n-doping of graphene. [6,7,43,44,47,51] Another family widely studied consists in the metallo-phthalocyanines, made up of a central metal ion and a conjugated macrocycle of alternating carbon and nitrogen atoms [33,43,46,[52][53][54][55][56][57] which give lower charge transfers (CT) compared to the aforementioned dopants. Indeed whereas the CT due to TCNQ/TCNE is in the range of a few tenths of electron transferred per molecule, [44,[47][48][49]51] phthalocyanine (Pc) molecules yield a weaker CT of a few hundredths of electron per molecule.…”