Atomistic Mechanisms of Codoping-Induced p- to n-Type Conversion in Nitrogen-Doped Graphene

TL;DR

This study uses first-principles calculations to explore how codoping nitrogen-doped graphene can switch its electronic type from p- to n-type or bipolar, addressing a key challenge for graphene electronics.

Contribution

It reveals atomistic mechanisms and identifies specific codopants that enable type conversion and defect healing in nitrogen-doped graphene.

Findings

B-, Al-, and P-codoping can repair vacancy defects in p-type NG.

Type conversion depends on nitrogen bonding configuration.

Codoping can restore charge transport properties.

Abstract

It was recently shown that nitrogen-doped graphene (NG) can exhibit both p- and n-type characters depending on the C-N bonding nature, which represents a significant bottleneck for the development of graphene-based electronics. Based on first-principles calculations, we herein scrutinise the correlations between atomic and electronic structures of NG, and particularly explore the feasibility of converting p-type NG with pyridinic, pyrrolic, and nitrilic N into n- or bipolar type by introducing an additional dopant atom. Out of the nine candidates, B, C, O, F, Al, Si, P, S, and Cl, we find that the B-, Al-, and P-codoping can anneal even relatively large vacancy defects in p-type NG. It will be also shown that, while the NG with pyridinic N can be converted into n-type via codoping, only the bipolar type conversion can be achieved for the NG with nitrilic or pyrrolic N. The amount of work function reduction was up to 0.64 eV for the pyridinic N next to a monovacancy. The atomistic origin of such diverse type changes is analysed based on Mulliken and crystal orbital Hamiltonian populations, which provide us with a framework to connect the local bonding chemistry with macroscopic electronic structure in doped and/or defective graphene. Moreover, we demonstrate that the proposed codoping scheme can recover the excellent charge transport properties of pristine graphene. Both the type conversion and conductance recovery in codoped NG should have significant implications for the electronic and energy device applications.