Beneficial impact of tunneling in nano-structured intermediate-band solar cell

TL;DR

This study demonstrates that incorporating a thin tunnel barrier in nano-structured intermediate-band solar cells enhances current and voltage by improving optical coupling and lifetime, leading to better overall efficiency.

Contribution

It introduces a detailed Green functions analysis showing the beneficial effects of tunneling barriers on electronic excitation, collection, and voltage in nano-structured solar cells.

Findings

Tunnel barriers improve intersubband optical coupling.

Broadened density-of-states increases radiative recombination.

Enhanced lifetime reduces Voc degradation.

Abstract

Using the non equilibrium Green functions formalism we propose a study of the electronic excitation and collection in nano-structured intermediate-band solar cell. We demonstrate that a thin tunnel barrier between the nano-objects and the host material is beneficial for both current and voltage. For the current, the confinement generated by such a thin barrier favors the intersubband optical coupling in the nano-objects and then improves the excitation-collection trade-off. We also show that a broadened density-of-state in the nano-objects increases the radiative recombination and then degrades the voltage. Using a detailed balance model we propose a broadening factor for this Voc degradation which decreases when a tunnel barrier enhances the life-time in the nano-objects.