Anisotropy of the charge-carrier mobility in polydiacetylene crystals

Abstract

The anisotropic mobility of excess charge carriers in pure and mixed crystals of two polydiacetylene derivatives was determined. The charge carriers were produced by pulsed irradiation and detected by time-resolved measurement of the microwave conductivity. The charge-carrier mobility was measured as a function of the orientation of the polymer backbone in the crystal with respect to the probing electric microwave field. A lower limit in the intrinsic anisotropy in the charge-carrier mobility was found to be 15 in favor of charge transport in the direction of the polymer backbone as compared to the transverse direction for polydiacetylene-(bis p-fluorobenzene sulfonate) (pFBS), while a value of 90 was found for polydiacetylene-(bis p-toluene sulfonate) (pTS) and the 50:50 pTS/FBS copolymer. A lower limit of the charge-carrier mobility along the backbone of 3 cm2/V s was found for both pTS and pFBS. The charge-carrier mobility in the copolymer was found to be one order of magnitude lower than in the pure polymers.