Structural determinants in the bulk heterojunction

Abstract

Photovoltaics is one of the key areas in renewable energy research with remarkable progress made every year. Here we consider the case of a photoactive material and study its structural composition and the resulting consequences for the fundamental processes driving solar energy conversion. A multiscale approach is used to characterize essential molecular properties of the light-absorbing layer. A selection of bulk-representative pairs of donor/acceptor molecules is extracted from the molecular dynamics simulation of the bulk heterojunction and analyzed at increasing levels of detail. Significantly increased ground state energies together with an array of additional structural characteristics are identified that all point towards an auxiliary role of the material's structural organization in mediating charge-transfer and -separation. Mechanistic studies of the type presented here can provide important insights into fundamental principles governing solar energy conversion in next-generation photovoltaic devices.

Electron Dynamics with Explicit-Time Density Functional Theory of the [4+2] Diels–Alder Reaction

“…The explicit-time-dependent DFT simulations were performed by means of a numerically stable algorithm that we applied in previous studies to predict the nonlinear electronic response in systems under the effect of external perturbations: − where ψ­( t ) is the nonstationary wave function at time­( t ), H is the Hamiltonian, and Δ t is the simulation time-step, here set to 0.0048 fs. The time dependence of the electronic wave function is calculated using a generalized Cayley algorithm, based on a Dyson-like expansion of the time-evolution operator, which conserves probability and preserves orthogonality.…”