Ultrafast charge carrier separation in Potassium-intercalated endohedral metallofullerene Sc$_3$N@C$_{80}$ thin films

TL;DR

This study demonstrates that potassium intercalation in endohedral metallofullerene thin films significantly accelerates charge carrier separation by providing an ultrafast exciton dissociation pathway, potentially improving photovoltaic efficiency.

Contribution

It introduces alkali metal doping as a novel method to enhance charge separation and reduce exciton trapping in molecular photovoltaic materials.

Findings

Potassium intercalation modifies exciton dynamics in Sc3N@C80 films.

Intercalation results in ultrafast exciton dissociation.

Enhanced free charge carrier generation observed.

Abstract

Molecular materials have emerged as highly tunable materials for photovoltaic and light-harvesting applications. The most severe challenge of this class of materials is the trapping of charge carriers in bound electron-hole pairs, which severely limits the free charge carrier generation. Here, we demonstrate a significant modification of the exciton dynamics of thin films of endohedral metallofullerene complexes upon alkali metal intercalation. For the exemplary case of Sc$_3$N@C$_{80}$ thin films, we show that potassium intercalation results in an additional relaxation channel for the optically excited charge-transfer excitons that prevents the trapping of excitons in a long-lived Frenkel exciton-like state. Instead, K intercalation leads to an ultrafast exciton dissociation coinciding most likely with the generation of free charge carriers. In this way, we propose alkali metal doping of molecular films as a novel approach to enhance the light to-charge carrier conversion efficiency in photovoltaic materials.