DC Hall-effect measurement for inkjet-deposited films of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) by using microscale gap electrodes

DC Hall-effect measurements were performed for inkjet-deposited p-type poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) films, site-selectively fabricated onto micrometer-scale van der Pauw electrode gap patterns. A commercially-available ink of high conductivity grade PEDOT/PSS was utilized. Carrier concentration and Hall mobility of the PEDOT/PSS containing ethylene glycol were in the order of 10²¹ cm^-3 and 0.1 cm²/(Vs), respectively, derived from the repeated Hall voltage measurements under reversal of current flow and magnetic field. The Hall voltage showed an n-type behavior, while the thermoelectric measurement indicated p-type. This sign anomaly of the Hall voltage, which is often observed in such low-mobility materials as amorphous silicon and chalcogenide glasses, may be due to hopping carrier transport in the PEDOT/PSS, although non-uniformities in the sample structure should be noted. Nonetheless this study suggests that the combination of microscale electrodes and inkjet deposition may be useful in high-sensitivity detection of Hall voltages for organic conducting films.