Photovoltaic effect for narrow-gap Mott insulators

TL;DR

This paper explores the photovoltaic effect in heterojunctions with doped Mott insulators, showing that impact ionization can significantly enhance efficiency by generating multiple electron-hole pairs from hot carriers.

Contribution

It introduces a novel approach to improve photovoltaic efficiency using narrow-gap Mott insulators and impact ionization within the Hubbard model framework.

Findings

Impact ionization enhances quantum efficiency in Mott insulator-based devices.

Hot electron/hole pairs can generate multiple electron-hole pairs rapidly.

Narrow-gap Mott insulators are promising for high-efficiency photovoltaics.

Abstract

We discuss the photovoltaic effect at a p-n heterojunction, in which the illuminated side is a doped Mott insulator, using the simplest description of a Mott insulator within the Hubbard model. We find that the internal quantum efficiency of such a device, if we choose an appropriate narrow-gap Mott insulator, can be significantly enhanced due to impact ionization caused by the photoexcited ``hot'' electron/hole pairs. Namely, the photoexcited electron and/or hole can convert its excess energy beyond the Mott-Hubbard gap to additional electrical energy by creating multiple electron/hole pairs in a time scale which can be shorter than the time characterizing other relaxation processes.