Structure and disorder in squaraine-C₆₀ organic solar cells: A theoretical description of molecular packing and electronic coupling at the donor-acceptor interface

Organic solar cells based on the combination of squaraine dyes (as electron donors) and fullerenes (as electron acceptors) have recently garnered much attention. Here, molecular dynamics simulations are carried out to investigate the evolution of a squaraine-C₆₀ bilayer interface as a function of the orientation and order of the underlying squaraine layer. Electronic couplings between the main electronic states involved in exciton dissociation and charge (polaron pair) recombination are derived for donor-acceptor complexes extracted from the simulations. The results of the combined molecular-dynamics-quantum-mechanics approach provide insight into how the degree of molecular order and the dynamics at the interface impact the key processes involved in the photovoltaic effect. A combined molecular dynamics-quantum mechanics approach reveals the complex landscape of the intermolecular electronic couplings at the squaraine-C₆₀ (donor-acceptor) bilayer interface as a function of the interfacial molecular packing and dynamics. Such aspects are of importance when considering the operation of organic solar cells.