A comparative study of charge mobility measurements in a diamine and in a hexaazatrinaphthylene using different techniques

Abstract

A comparative study of hole-mobility in N,N '-diphenyl-N,N '-di(3-methylphenyl)(1,1 '-biphenyl)-4,4 '-diamine (TPD) using three independent measurement techniques is presented. Time-of-flight (TOF), steady-state space charge-limited current (SCLC) experiments are carried-out in neat films of TPD, sandwiched between electrodes with different work functions. Organic field-effect transistors (OFET) are fabricated from TPD thin films and their electrical properties characterized. The comparative results show that all-electrical measurements that involve carrier injection from a metal electrode into the organic film yield effective mobility values that are one order of magnitude lower than those obtained from time-of-flight experiments in which carriers are created in the film optically. Similarly, SCLC and TOF experiments were used to measure electron-mobility in a discoid organic compound 2,3,8,9,14,15-hexakis-dodecylsulfanyl-5,6,11,12,17,18-hexaazatrinaphthylene (HATNA-(SC12H25)(6)).