Molecular Dynamics Simulation of Photovoltaic Exciton Dissociation

The dynamics of exciton particles in photovoltaic systems plays a key role in determining the electrical efficiency of such systems. Excitons consist of electron-hole pairs that generate electric currents through dissociation, and a quantitative understanding of exciton dynamics is relevant to the design of efficient photovoltaics. This rate of dissociation is known to depend on the degree of orbital energy disorder prevailing over the molecular lattice of the photovoltaic, and this dependence has previously been investigated using kinetic Monte Carlo techniques that employ pre-assigned lattice site transition rate constants and static lattice sites.

In this study, we simulate this dissociation process using accelerated molecular dynamics (MD), which accommodates lattice vibrations and allows lattice site transitions based on particle dynamics. Treating the electron and hole as separate particles, we investigate the time-averaged separation between these particles over the course of multiple trial simulations and calculate their fractional dissociation yield. The energetic disorder of the lattice is varied and the corresponding fractional dissociation yield of the exciton is determined and compared with experimental results.