In the context of this work the
materials Alpha -NPD and MoO3, as well as samples of varying Alpha -NPD:MoO3 doping
concentration have been investigated. The measured spectra of Alpha -NPD have been
compared, and found to be in good agreement with calculations based on density
functional theory. In situ measurements in the middle infrared range show spectral
changes of the vibronic excitation as a function of the doping concentration. The
intensity of spectral change has been determined via an optical model in the analytical
software SCOUT and fits nicely with the formation of Alpha -NPD:MoO3 charge
transfer complexes in the film. Using this approach the efficiency of charge transfer
for MoO3 in Alpha -NPD has been determined to 6.5 %. Additional ex situ measurements
in the near infrared range show a similar behavior as a function of the doping
concentration for an electronic excitation, which has already been assigned to an
Alpha -NPD:MoO3 charge transfer complex in the literature. By comparing the two
observed excitations this assignment has been verified, and by usage of DFT based
calculations of the Alpha -NPD cation extended to the vibronic excitations. |
