An electronic ratchet is required in nanostructured intermediate band solar cells

TL;DR

This paper analyzes the limitations of nanostructured intermediate band solar cells and proposes that incorporating an electronic ratchet mechanism can overcome these challenges, enabling higher efficiencies.

Contribution

It demonstrates that electronic ratchets reduce sensitivity to nanostructure limitations and highlights advantages of quantum well devices over quantum dots.

Findings

Electronic ratchets improve efficiency robustness.

Quantum wells outperform quantum dots in this context.

Current materials cannot surpass single junction cell efficiencies.

Abstract

We investigate in this letter the intrinsic properties that have limited the efficiency of nanostructured intermediate band solar cells. Those devices take advantage of intra-band transitions, which occur on narrow energy width, and present low radiative recombination efficiency. We derive the minimum requirements in terms of those two characteristics to achieve efficiencies in excess of the Shockley-Queisser limit, and show that compatible nanostructures are challenging to obtain. Especially, we evidence that currently experimentally considered materials cannot overcome the best single junction cells. In order to solve those issues, we consider devices including an electronic ratchet mechanism. Firstly, such devices are shown to be much less sensitive on the limitations of the nanostructures characteristics, so that requirements for high efficiencies can be met. Secondly, we show that quantum well devices present advantages over their quantum dots counterparts, although they have attracted much less interest so far.