Development of MWCNT thin film electrode transparent in the mid-IR range

In this research carbon nanotube-based thin film electrodes, with high transparency in mid-infrared range, were developed as a replacement for indium fin oxide electrodes. The thin film electrodes were prepared from polyelectrolyte and mull-walled carbon nanotubes by layer-by-layer assembly. Polyethyleneimine (PEI) and carboxylic mull-walled carbon nanotubes (MWCNT-COOH) were deposited alternately on glass substrates. Samples with different number of bilayers (PEI + MWCNT-COOH) were prepared. Thickness of the films varied between 80 and 240 nm, depending of the number of bilayers. After deposition of each bilayer, the samples were dried at 120 degrees C for 10 min. The fabricated films were characterized using Raman spectroscopy, high-resolution scanning microscopy (HRSEM) and transmission electron microscopy (TEM). Transparency of the films was measured in UV/Vis and IR ranges, utilizing UV/Vis spectrophotometer and FTIR spectrometer respectively. Sheet resistance of the films was measured with four-point probe method and the resistance values obtained were ranging from 6 k Omega/sq up to 23 k Omega/sq, depending on the number of layers.