Photothermal Radiometry analysis of charge transport

Photothermal techniques have been applied successfully in the study of the charge transport process in inorganic semiconductors in crystalline and polycrystalline form. Photothermal radiometry is a non-contact technique that could provide not only the thermal properties but also parameters related with recombination of charge. In this work the potential of photothermal radiometry in the study of charge recombination in organic polymeric semiconductors is explored. It has been shown that conjugated polymers are especially interesting for its charge transport properties. In this work, polyaniline samples grown on stainless steel by electrochemical methods are studied. Photothermal radiometry profiles were obtained by illuminating the sample with modulated light of an ion Argon laser and detecting the changes of temperature with an IR detector. The profiles show marked differences depending on the conditions of preparation. In order to determine the effects of charge recombination, and at the same time to eliminate the influence of the roughness of the different samples, a normalization procedure was devised. This procedure consisted in dividing the signal of the sample with charge recombination effects by the signal of the sample that would not present charge recombination. Our results are discussed and compared with an inorganic semiconductor.