Paper 2D-ThP9
Enhanced Electrical Conductivity of Transparent Carbon Nanotube Sheet by Acid Treatment

Thursday, November 13, 2014, 6:00 pm, Room Hall D

Enhanced electrical conductivity of transparent carbon nanotube sheet by acid treatment

Jinhong Kim, Daewoong Jung, Maeum Han and Gil S. Lee^*

Department of Electrical engineering, University of Texas at Dallas, Richardson, Texas, USA

Fax: +1-(972)-883-6839 E-mail address: gslee@utdallas.edu

Considerable efforts were dedicated to fabricate flexible transparent conductive films (TCFs) with high transmittance and low resistance for utilizing in various applications. To date, the most commonly used material for TCFs is indium tin oxide (ITO) due to its high transparency and low electrical resistance. However, there are several disadvantages with using ITO films in future applications, such as the brittleness and problems with polymer substrates. Recently, researches focused on developments in flexible TCFs, either through optimized structural configuration or exploring new materials to replace ITO films.

Carbon nanotubes (CNTs) have received increasing attentions as ITO replacement due to their excellent mechanical, electrical, thermal properties. Our previous work produced transparent, conductive CNT sheets by using a simple spinning method [1-2]. These CNT sheets had sheet resistances of 0.75-1 kΩ/sq and transmittances of ~85-90 %. However, there was a trade-off effect between sheet resistance and transmittance of TCFs during transferring process of CNTs. An increasing number of CNT layers in the TCFs can decrease the sheet resistance as well as the transmittance, simultaneously. Therefore, key challenge is how to realize the highly conductive CNT sheet without a degrading of transmittance.

Simple acid treatment was conducted to improve the electrical conductivity of the CNT sheets. The transferring CNT sheets on glass substrates were immersed in 60 % nitric acid for 1 hour. After the acid treatment, highly conductive CNT sheets were obtained with slightly increased transmittance. The acid treatment leads further inter-connection between the individual CNTs to form continuous electrical pathway, result in high conductivity of the CNT sheet. These results lead us to believe that the CNT sheets with low sheet resistance (450 Ω/sq) and high optical transmittance (90%) can be potential candidate for flexible TCF applications.

Reference

1. Jung et al, Sens Actuators A199 (2013), 176.