Fabrication and Characterization of Conductive Transparent Film Based on Carbon Nanotube for Optoelectronic Devices

Optoelectronic devises are an integral part of our modern society. From the screens on our electronic computers to the solar panels that will hopefully replace fossil fuel sources, the need for theses devices and advancements for their sustainability and improved mass production is a large area of interest. A common component of all of these devices is a conductive and transparent cathode, usually transparent conducting oxides (TCOs). The downfall of TCOs is their degradation and incompatibility with progressive flexible substrates as their resistivity increases significantly with flexing and environmental exposure.

This study involved the fabrication and characterization of a multi-walled carbon nanotube (MWCNT) and sodium lauryl sulfate (SDS) composite deposited over polyethylene terephalate. The cathode materials have shown drastically effect of the performance of both organic and dye sensitized solar cells. The roughness of the films and electronic absorbance spectra are important as roughness increases the surface area over a two dimensional area and has shown to improve efficiency in solar cells. Also the absorbance spectrum of the film would need to be complementary to the photovoltaic material.

 

Figure 1: Electronic absorbance spectra of the MWCNT:SDS thin film that has been background corrected for PET.

Figure 1 shows the absorption spectra from both UV-Vis and IR ranges. The spectrum shows decreases in transmittance at 635 nm, 115 1nm, 1201 nm, 1223 nm, and 1630 nm. These absorbance peaks would not interfere with poly(3-hexylthiophene-2,5-diyl) (P3HT) that has a strong broad maxima at 525nm that extends between 400nm and 600nm [1]. The roughness (Ra) value of the MWCNT:SDS film is much greater at 21.8 nm as compared to 0.59 nm for unannealed ITO films [2].

References

1. Boland, P.; Sunkavalli, S.S.; Chennuri, S.; Foe, K.; Abdel-Fattah, T.M.; Namkoong, G. Inversigation of structural, optical, and electrical properties of regioregular poly(3-hexylthiophene)/fullerene blend nanocomposites for organic solar cells. 2010. Thin Solid Films. 518 1728-1731.
2. Raoufi, D.; Kiasatpour, A.; Fallah, H.R.; Rozatian, A.S.H. Surface characterization and microstructure of ITO thin films at different annealing temperatures. 2007. Appl. Surf. Sci. 253 9085-9090.