Electrical conductivity manipulation and switching phenomena of poly(p-phenylenebenzobisthiazole) thin film by doping process

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Abstract
Current–voltage (i-v) characteristics of dry poly(p-phenylenebenzobisthiazole) (PBZT) thin films are studied before and after various doping processes. Conductivity switching phenomenon is observed after doping with HCl and H2SO4 acidic solutions at different concentration levels. The conductivity is 10 folds higher in a relatively high sweeping voltage range (0.2–0.3 V) than that sweeping in a lower range of 0–0.1 V. The conductivity switching phenomenon becomes more obvious with an increase of acid concentration. HCl shows to be more favorable for a quick and efficient switching behavior than H2SO4. The reduction of PBZT with metal (Fe, Cu and Pd) doping process produces linear conductivity along the whole sweeping range of voltage. A 30% electrical conductivity enhancement is observed after applying an external dc voltage on the acid soaked PBZT film and different voltages enhance the conductivity to the same level. The conductivity returns gradually after removing the applied voltage. Four-point probe conductivity measurements, FT-IR, scanning electron microscopy, EDAX elemental analysis, X-ray diffraction and TGA thermal analysis were used for better understanding the doping processes and conductivity switching mechanisms. A molecular structure transformation during the doping process is proposed.