Dispersibility of vapor phase oxygen and nitrogen functionalized multi-walled carbon nanotubes in various organic solvents.

Maryam Khazaee,Gerhard Lackner,Mark Rümmeli,Wei Xia,Martin Muhler,Doru C. Lupascu,Rafael G. Mendes

doi:10.1038/srep26208

Abstract

The synthesis and characterization of gas phase oxygen- and nitrogen-functionalized multi-walled carbon nanotubes (OMWCNTs and NMWCNTs) and the dispersibility of these tubes in organic solvents were investigated. Recently, carbon nanotubes have shown supreme capacity to effectively enhance the efficiency of organic solar cells (OSCs). A critical challenge is to individualize tubes from their bundles in order to provide homogenous nano-domains in the active layer of OSCs. OMWCNTs and NMWCNTs were synthesized via HNO3 vapor and NH3 treatments, respectively. Surface functional groups and the structure of the tubes were analyzed by temperature-programmed desorption, Fourier transform infrared spectroscopy, transmission electron microscopy, and Raman spectroscopy which confirmed the formation of functional groups on the tube surface and the enhancement of surface defects. Elemental analysis demonstrated that the oxygen and nitrogen content increased with increasing treatment time of the multi-walled carbon nanotube (MWCNT) in HNO3 vapor. According to ultra-violet visible spectroscopy, modification of the MWCNT increased the extinction coefficients of the tubes owing to enhanced compatibility of the functionalized tubes with organic matrices.

Highlights

This research aims to find out the nature of chemical doping of Multi-walled carbon nanotubes (MWCNTs) and their dispersion capability in organic solvents
Functionalization of tubes by oxygen and nitrogen resulted in the creation of a bumpy morphology in all of the functionalized tubes which may be attributed to the introduction of new defects on the carbon nanotubes (CNTs) sidewalls
The amount of amorphous carbon was enormously decreased on the functionalized tubes sidewall, as compared with pristine MWCNT

Summary

Introduction

In recent years, utilizing CNTs in bulk heterojunction (BHJ) solar cells has attracted much attention due to their superior electrical properties[20]. For this purpose, proper individualization of CNTs in organic solvents is indispensable, because it facilitates their incorporation into photovoltaically active matrices providing nano-domains in the BHJ. The out of plane unhybridized Pz orbitals of CNTs form an appropriate pathway for transporting charge to the electrodes[22] These effects can enhance solar cell efficiency[23]. This research aims to find out the nature of chemical doping of MWCNTs and their dispersion capability in organic solvents Understanding these phenomena is essential and beneficial for their subsequent usage e.g. in BHJ solar cells

Objectives

Methods

Results