LUTETIUM BISPHTHALOCYANINE THIN-FILMS FOR GAS-DETECTION

The bisphthalocyanine of lutetium, Pc2Lu, is the first intrinsic molecular semiconductor, with a high concentration of intrinsic charge carriers and a low thermal activation energy of conduction. The redox potentials of Pc2Lu, which is more easily oxidized and reduced than conventional metal phthalocyanines, make it possible to obtain the intrinsic semiconducting properties. The possibility of using Pc2Lu as the sensitive element of a gas sensor is studied. This paper describes the absorption spectra of thin films of Pc2Lu and their changes during oxidation or reduction induced by gases such as HCl, Cl2, H2S and SO2. Special attention is given to the action of NO2 on the conductivity and the corresponding thermal activation energy, whose evolution is interpreted in terms of variations of carrier concentration and mobility.