Nearly ohmic hole injection

Nearly Ohmic Hole Injection in Phenylamine-Based Compounds... 

Hence, r is equal to 1 if the hole injection efficiency is 100%, and the contact can be viewed as truly ohmic. On the other hand, t) should be less than 1 if the contact is Schottky. Figure 3.24 shows t) (solid squares) vs the nominal hole injection barrier at a field strength f=0.1MV/cm. The open circles are the ratios of mobilities derived from DI experiments (Xdi to the TOF-derived hole mobilities p. Moreover, the open triangles are ratios of AS-derived mobilities Pas to the average hole mobilities derived from TOF For the ohmic contact of PEDOTPSS/MTDATA, rj 1 and the hole injection approaches an efficiency of nearly 100%. Meanwhile, the injection efficiency for NPB is lowered to about 70%, but the nominal hole mobilities derived from Dl and AS reach 90% and 100% of the TOF-derived mobility value respectively. For the contact of TPD, the injection efficiency and the nominal hole mobilities are less than 80%. Therefore, PEDOTPSS forms the worst contact with TPD among those PA compounds. 

Once ohmic contacts are formed, electrons and holes can be injected and transported to the insulating region near the center of the film where radiative recombination occurs. 

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