Spectral-Luminescent and Electroluminescent Properties of Charge-Transfer Systems Based on Electron-Donating Diphenylamine Derivatives and Acceptors of Dibenzothiophene Sulfone and Phenanthridine

Spectral characteristics and luminescence under the photo- and electro-excitation of substituted dibenzthiophene sulfone and phenanthridine were studied in this paper. Diphenylamines are substituents introduced in the 2nd and 7th positions (linear configuration) or the 3rd and 6th positions (angular configuration) of dibenzthiophene sulfone or phenanthridine. All molecules show delayed fluorescence, both in solutions and films produced by thermal vacuum deposition. The value of the energy gap between the S1 and T1 states has been estimated and is shown to depend not only on the spatial arrangement of the fragments among themselves (linear or angular), but also on the nature of the substituent in diphenylamine. The highest electroluminescence brightness was found for the molecules, in which triplet levels are involved, both through the process of triplet-triplet annihilation and through thermally activated delayed fluorescence.

Fabrication of Polymer Light Emitting Diodes by Layer-by-Layer Complexation Technique

Multilayer films were fabricated employing a new layer-by-layer complexation technique by alternatively dipping substrates in solutions of macromolecular ligands and Eu3+ ions. A luminescent poly[2-(3-thienyl)ethanol hydroxycarbonyl-methyl urethane] (H-PURET) was prepared by hydrolysis of thiophene polymer, poly[2-(3-thienyl)ethanol butoxycarbonyl-methyl urethane] (PURET), which was developed in our laboratory. H-PURET was used as macromolecular ligands. The multilayer deposition was monitored using UV-visible spectroscopy. As the number of bilayers increases, the absorption due to the polymer increases. The multilayer films were characterized by infrared and fluorescence spectroscopic techniques. Electroluminescence brightness easily obtained from the multilayer film of conjugated polymer-Eu3+ complex was measured to be about 40nW.