Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.252, 195-204, 1994
Temperature and Field-Dependence of Hole Transport in Chloroaluminum Phthalocyanine Determined by Time-of-Flight Measurements
Using the time-of-flight technique, drift mobility measurements were performed on the p-type semiconductor chloroaluminum phthalocyanine (ClAIPc). The field dependence of the hole mobilities was examined at different temperatures, and the results were found to be interpretable within the context of the disorder formalism developed by H. Bassler and coworkers. In the region of low applied fields the mobilities are seen to first decrease with increasing field, for all the temperatures in the range studied. The mobility then reaches a distinct minimum at intermediate fields which is followed by an increase at higher fields. The high field behaviour for all temperatures studied shows a linear dependence of 1n mu vs E(1/2), the slope of which decreases with increasing temperature with values ranging from 9.15x10(-3) (cm/V)(1/2) at 265 K to 5.25x10(-3) (cm/V)(1/2) at 330 K. Mobilities at all applied fields were found to increase with rising temperatures showing a linear dependence of 1n mu vs T-2. At each temperature, measurements were taken for applied fields of 2.5x10(4) V cm(-1) to 1.9x10(5) V cm(-1). The mobilities at the highest applied field ranged from 6.05x10(-5)cm(2)V(-1) s(-1) at 265K to 1.15x10(-4) cm(2)V(-1)s(-1) at 330K. In view of the apparent consistency of this system’s behaviour with that predicted by the disorder formalism, the relevant constants were calculated and their relationships examined to better determine the correlation with the proposed model. From mu (E=0) mu 0 exp-(T-0/T)(2) and the appropriate plot, the values for mu(0) and T-0 are 2.5x10(-3) cm(2)V(-1)s(-1) and 777 K respectively. This yields a distribution width sigma of 0.1 eV and corresponding