Impact of nanostructure configuration on the photovoltaic performance of quantum dot arrays

TL;DR

This study uses a mesoscopic model to analyze how nanostructure configurations in quantum dot arrays affect their photovoltaic efficiency, highlighting the roles of inter-dot and contact couplings in charge dynamics.

Contribution

It introduces a detailed non-equilibrium Green's function model linking nanostructure design to optoelectronic performance in quantum dot solar cells.

Findings

Inter-dot coupling influences the joint density of states and band gap.

Dot-contact coupling critically affects charge extraction efficiency.

Long carrier lifetimes emphasize the impact of inter-dot coupling on device performance.

Abstract

In this work, a mesoscopic model based on the non-equilibrium 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 inter-dot 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 inter-dot 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.