Effects Related to the Donor Functionality

Attempts to relate hole mobilities to the structure of the donor molecule or functionality have been based on dipole moment, ionization potential, and charge delocalization arguments. 

There have been several attempts to relate mobilities to ionization or oxidation potentials (Enokida et al., 1990 Scott et al., 1990 Kanemitsu et al., 1991, 1992 Kitamura and Yokoyama, 1991). Scott et al. studied a series of hydrazone compounds in a polyarylate. The oxidation potentials of the donor compounds varied from 0.53 to 1.04 V. The results showed that the zero-field mobilities increase with increasing oxidation potential. In contrast, Enokida et al. investigated a series of butadiene, hydrazone, and oxadiazole compounds doped into a PC and concluded that the mobilities increased with decreasing ionization potential. Kitamura and Yokoyama studied a series of hydrazone compounds in a PC and concluded that the mobilities were independent of the ionization potential. While the reason for these discrepancies is not clear, it should be noted that the study of Scott and coworkers involved zero-field 

---