First-principles stochastic Schrödinger dynamics of photoinduced charge separation: Full quantum evolution in ZnPc-F8ZnPc aggregates.

Abstract

The photoinduced charge separation in donor-acceptor materials is key to improving organic solar cell efficiency. However, it is complex due to the interplay of electronic excited states, molecular vibrations, and morphology. Here, we investigate this process in ZnPc-F8ZnPc aggregates using first-principles quantum dynamics. We construct the diabatic excited states from fragment particle-hole densities and simulate the dynamics via the stochastic Schrödinger equation. The results show that charge separation involves three hybrid steps: energy/charge transfer, vibronic coherence, and entropy enhancement. In 100 fs, local excitation (LE) and charge transfer (CT) states relax to lower energy states, forming a quasi-stationary distribution. This involves interfacial energy transfer and exciton dissociation. Then, CT states coherently interact with LE states via C-N and C-C bond vibrations for 300 fs, aiding charge separation. Finally, free charges form due to entropy enhancement. This work demonstrates a novel approach to studying photophysics in complex systems. It unifies several charge separation mechanisms and highlights the importance of interfacial energy transfer for enhancing photovoltaic performance.