| Abstract [eng] |
Organic semiconductors showed great potential in many real-life applications including organic light-emitting diodes (OLEDs) and optical sensors. Despite previous achievements for organic semiconductors in the field of organic electronics, there are still no such ideal semiconductors, but scientific community is looking for them. The aim of this work is to discover the potential of isomeric compounds in electronic devices and optical oxygen sensors. Different properties of the compounds were investigated, devices were fabricated, and their performances in potential applications were determined. Competition of room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) was investigated on four newly synthesized organic isomeric compounds, TPA23DBT, TPA24DBT, TPA26DBT, and TPA35DBT, containing two electron-donating triphenylamine moieties and single electron-accepting dibenzothiophene-2-yl(phenyl)methanone unit by numerous theoretical and experimental approaches. Diversity of the emission origin (RTP or TADF) of the isomeric compounds was caused by different energy gaps (0.09-0.39 eV) between the lowest singlet and triplet states that are locally exited and charge transfer in nature. The effect of the competition of RTP and TADF on the performance of electronic devices and optical sensors of oxygen is demonstrated and discussed. Very different external quantum efficiencies, ranging from 2.8 to 13.9%, were observed for green phosphorescent organic light-emitting diodes which were fabricated using the isomeric compounds as hosts. Such differences in device efficiency were partly related to the different hole mobility values. The hole mobilities of ca. 1×10-3 cm2V-1s-1 were observed at electric field of 6.4×105 V/cm for the derivatives having triphenylamine moieties at C-2, C-4 (TPA24DBT) and at C-3, C-5 (TPA35DBT) positions of the central benzene ring. Considerably lower hole mobilities of ca. 1×10-5 cm2 V-1 s-1 were recorded at the same electric field for the compounds with triphenylamine groups at C-2, C-3 (TPA23DBT) and at C-2, C-6 (TPA26DBT) positions. Depending on the great extent on RTP and TADF processes, different efficiencies of long persistent luminescence (LPL) of the exciplex-forming solid-state mixtures of the isomers and bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) were detected. The compound with triphenylamine groups at C-3, C-5 (TPA35DBT) positions as RTP emitter and its molecular mixture with DPEPO as LPL emitter for the active layers of optical sensors of oxygen were prepared. They showed the Stern–Volmer constant of 4.55×10-4 ppm in the range of oxygen concentrations of up to 10000 ppm. |
