Ultrahigh-performance transparent conductive films of carbon-welded isolated single-wall carbon nanotubes.

Abstract

Single-wall carbon nanotubes (SWCNTs) are ideal for fabricating transparent conductive films because of their small diameter, good optical and electrical properties, and excellent flexibility. However, a high intertube Schottky junction resistance, together with the existence of aggregated bundles of SWCNTs, leads to a degraded optoelectronic performance of the films. We report a network of isolated SWCNTs prepared by an injection floating catalyst chemical vapor deposition method, in which crossed SWCNTs are welded together by graphitic carbon. Pristine SWCNT films show a record low sheet resistance of 41 ohm □^-1 at 90% transmittance for 550-nm light. After HNO₃ treatment, the sheet resistance further decreases to 25 ohm □^-1. Organic light-emitting diodes using this SWCNT film as anodes demonstrate a low turn-on voltage of 2.5 V, a high current efficiency of 75 cd A^-1, and excellent flexibility. Investigation of isolated SWCNT-based field-effect transistors shows that the carbon-welded joints convert the Schottky contacts between metallic and semiconducting SWCNTs into near-ohmic ones, which significantly improves the conductivity of the transparent SWCNT network. Our work provides a new avenue of assembling individual SWCNTs into macroscopic thin films, which demonstrate great potential for use as transparent electrodes in various flexible electronics.