New Transparent Metal-like Bilayer Composite Films with Highly Conducting Layers of θ-(BET-TTF)2Br·3H2O Nanocrystals

Abstract

A flexible low-density metallic material, which is extremely transparent, was obtained using as active component the highly conducting molecular metal θ-(BET-TTF)2Br·3H2O, BET-TTF = bis(ethylenethio)tetrathiafulvalene. This material is a bilayer (BL) film that was prepared by treating a polycarbonate film containing 2 wt.-% of molecularly dispersed BET-TTF with vapor of a Br2/CH2Cl2 solution. Optimum conditions for the preparation of very transparent metallic materials were established. The X-ray diffraction patterns indicate that the conducting layer of the BL films is formed by well a* oriented θ-(BET-TTF)2Br·3H2O nanocrystals, which are clearly observed in the SEM images. Conductivity measurements confirm that the nanocrystalline layers have the same transport properties as those of the single crystals, displaying metal-like behavior down to He temperature and the highest room temperature conductivity (120 Ω–1 cm–1) reported so far for this kind of film.