Multiple exciton generation and giant external quantum efficiency in VO$_2$

TL;DR

This paper reports the first experimental observation of multiple exciton generation in VO$_2$, leading to a record external quantum efficiency of 170% at room temperature, highlighting potential for advanced solar cell applications.

Contribution

It demonstrates MEG in a strongly correlated material VO$_2$, showing a significant increase in quantum efficiency, which was not previously observed in such materials.

Findings

MEG observed in VO$_2$ at room temperature

EQE enhanced to ~170% with specific photoexcitation

MEG correlates with electron correlation strength

Abstract

Multiple exciton generation (MEG) is a widely studied phenomenon in semiconductor nanocrystals and quantum dots wherein photo-excited carriers relax by generating additional electron-hole pairs. Here, we present the first experimental observation of MEG and the same leading to giant external quantum efficiency (EQE) in VO$_2$, a prototype strongly correlated material. By employing a photoexcitation (lamda ~ 488 nm) of ~ 4.2 times the bandgap, EQE in VO$_2$ is enhanced up to ~ 170 % at room temperature. Temperature dependent experiments exhibit the direct relation between MEG and strength of electron correlation and suggest that such a phenomenon could be exploited in large number of strongly correlated materials for high performance solar cell research in near future.