Doping Effects and Electronic States in C60-Polymers

TL;DR

This study investigates how doping and conjugation affect the electronic structures of C60-polymers, revealing transitions between insulating and metallic states using a semiempirical model.

Contribution

It provides new insights into the electronic state transitions in C60-polymers under various doping levels and conjugation conditions.

Findings

Neutral C60-polymer can be a direct-gap insulator or metal.

Doping with one electron per molecule results in metallic behavior.

Two-electron doping causes a transition from indirect to direct-gap insulator.

Abstract

Band structures of C60-polymers are studied changing conjugation conditions and the electron number. We use a Su-Schrieffer-Heeger type semiempirical model. In the neutral C60-polymer, electronic structures change among direct-gap insulator and the metal, depending on the degree of conjugations. The C60-polymer doped with one electron per one molecule is always a metal. The energy difference between the highest-occupied state and the lowest-unoccupied state of the neutral system becomes smaller upon doping owing to the polaron effects. The C60-polymer doped with two electrons per one C60 changes from an indirect-gap insulator to the direct-gap insulator, as the conjugations become stronger.