**7. Conclusions**

The novel zinc-chelate complexes of sulphanilamino-substituted quinolines and benzothiazoles are proper materials for OLEDs, with efficient exciplex emission giving rise to white OLEDs and OLEDs of different colors including blue, green, and yellow. Exciplex emission can also be observed in the PL spectra of the films containing blends of zinc complex and hole-transporting material. The main reason of effective exciplex formation for these compounds is probably the presence of a spatially extended, electron-rich amine segment in the zinc complex molecule which can enhance its ability of intermolecular interactions with the molecules of the hole-transporting layer and hence magnify the possibility of exciplex forming. Material of the hole-transporting layer is crucial for the efficiency of exciplex formation. Triarylamine derivatives like NPD or PTA seem to be the most proper materials for exciplex formation. Exciplexes can be eliminated with only intrinsic bands remaining in the EL spectra when the hole-transporting layer is not a triarylamine drivative. This may be due not only to positions of energy levels but also to good spatial overlap and high electron density on amino groups of both zinc complex and triarylamine derivatives. The relation between intrinsic and exciplex EL bands for the EL devices depends not only on the material of hole-transporting layer but also on the applied voltage. This may be due to to the shift of the carrier recombination zone from the interface of hole-transporting and emitting layers to the bulk of the emitter layer.
