Impact of Nanostructure Configuration on the Photovoltaic Performance of Quantum-Dot Arrays

In this paper, a mesoscopic model based on the nonequilibrium Green's function formalism for a tight-binding-like effective Hamiltonian is used to investigate a selectively contacted quantum-dot array designed for operation as a single-junction quantum-dot solar cell. By establishing a direct relation between nanostructure configuration and optoelectronic properties, the investigation reveals the influence of interdot and dot-contact coupling strengths on the rates of charge-carrier photogeneration, radiative recombination, and extraction at contacts, and, consequently, on the ultimate performance of photovoltaic devices with finite quantum-dot arrays as the active medium. For long carrier lifetimes, the dominant configuration effects originate in the dependence of the joint density of states on the interdot coupling in terms of band width and effective band gap. In the low-carrier-lifetime regime, where recombination competes with carrier extraction, the extraction efficiency shows a critical dependence on the dot-contact coupling.