Nitrogen-tailored quasiparticle energy gaps of polyynes

TL;DR

This study uses the GW method to explore how nitrogen doping affects the quasiparticle energy gaps and electronic properties of polyynes, revealing new ways to tailor their characteristics.

Contribution

It provides the first detailed analysis of nitrogen doping effects on polyyne electronic properties using advanced computational methods.

Findings

Nitrogen doping alters the quasiparticle energy gap depending on the substitution site.

Doping shifts the Fermi level closer to the LUMO, indicating n-type behavior.

The effect is most pronounced when a nitrogen atom replaces a carbon near the hydrogen end.

Abstract

Polyyne, a sp1-hybridized linear allotrope of carbon, has a tunable quasiparticle energy gap, which depends on the terminated chemical ending groups as well as the chain length. Previously, nitrogen doping was utilized to tailor the properties of different kinds of allotrope of carbon. However, how the nitrogen doping tailors the properties of the polyyne remains unexplored. Here, we applied the GW method to study the quasiparticle energy gaps of the N-doped polyynes with different lengths. When a C atom is substituted by a N atom in a polyyne, the quasiparticle energy gap varies with the substituted position in the polyyne. The modification is particularly pronounced when the second-nearest-neighboring carbon atom of a hydrogen atom is substituted. In addition, the nitrogen doping makes the Fermi level closer to the lowest unoccupied molecular orbital, resulting in a n-type semiconductor. Our results suggest another route to tailor the electronic properties of polyyne in addition to the length of polyyne and the terminated chemical ending groups.