Dual versus normal TADF of pyridines ornamented with multiple donor moieties and their performance in OLEDs. Issue 11 (2nd March 2021)

• Record Type: Journal Article
• Authors: Arsenyan, Pavel; Vigante, Brigita; Leitonas, Karolis; Volyniuk, Dmytro; Andruleviciene, Viktorija; Skhirtladze, Levani; Belyakov, Sergey; Grazulevicius, Juozas Vidas
• Is Part Of: Journal of materials chemistry. Volume 9:Issue 11(2021)
• Page Start: 3928
• Page End: 3938
• Publication Date: 2021-03-02
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0tc05745b
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Pyridine ring in novel dicyanopyridines exists in a twist-conformation in solid state. Green and orange OLEDs with 3, 6-di- tert -butyl-carbazole-containing emitter exhibiting normal TADF, showed high maximum EQE of 25%. Abstract : A procedure for post-functionalization by 3, 6-di- tert -butyl-carbazole or 3, 7-dibromophenothiazine of dicyanopyridines was developed. Pyridine rings in new pyridines exist in a twist-conformation in the solid state. Green and orange thermally activated delayed fluorescence (TADF) with close emission quantum yields in solid-state resulting from recombination of two different intramolecular charge transfer (ICT) states was observed for compounds post-functionalized by 3, 6-di- tert -butyl-carbazole and 3, 7-dibromophenothiazine moieties, respectively. Non-doped and doped organic light-emitting diodes exhibiting green and orange electroluminescence were developed using the synthesized compounds as normal/dual TADF emitters. The device based on 3, 7-dibromophenothiazine-containing emitters exhibiting dual TADF showed low device life-times and a low maximum external efficiency of 3.1 (for the non-doped device) and 5% (for the doped device). Organic light-emitting diodes with 3, 6-di- tert -butyl-carbazole-containing emitters exhibiting normal TADF showed relatively high device life-times and a high maximum external efficiency of 8.1 (for the non-doped device) and 25% (for the doped device). Because of the energy distribution between the two ICT states in dual-TADF emitters, ultra-long lifetime of fluorescence (up to milliseconds) was detected which results in exciton–exciton and exciton–polaron annihilations under electrical excitation and low stability and efficiency of the device.