Time‐of‐Flight Method for Determining the Drift Mobility in Organic Semiconductors

Electronic properties of organic semiconductors are determined by the carrier density and carrier mobility. The time-of-flight (TOF) method is one of the techniques used for the measurement of the drift mobility of charge carriers, unlike the microwave conductivity method and Hall measurement, which provide the band mobility. This chapter describes the principle, experimental setup, sample preparation, and characteristic features of TOF measurement. In TOF experiments, charge carriers move from one edge of the samples to another. During the charge carrier movement, they interact with localized states formed by impurities and defects. Therefore, the TOF experiment affords the drift mobility of charge carriers in the bulk of the samples. In addition to the conventional TOF method, the xerographic TOF, lateral TOF, pulse-voltage TOF, and dark injection space charge-limited transient current techniques are used for the measurements of the charge carrier mobilities of organic semiconductors.