O. Bezvikonnyi “Investigation of new organic semiconductors for organic light emitting diodes” doctoral dissertation defence

Thesis Defense

Author, Institution: Oleksandr Bezvikonnyi, Kaunas University of Technology

Science area, field of science: Technological Sciences, Materials Engineering, T008

Scientific Supervisor: prof. habil. dr. Juozas Vidas Gražulevičius (Kaunas University of Technology, Technological Sciences, Materials Engineering, T008).

Dissertation Defence Board of Humanities, Materials Engineering Science Field:
Prof. Dr. Habil. Sigitas Tamulevičius (Kaunas University of Technology, Technological Sciences, Materials Engineering, T008) – chairman,
Dr. Mindaugas Andrulevičius (Kaunas University of Technology, Technological Sciences, Materials Engineering, T008),
Prof. Dr. Saulius Grigalevičius (Kaunas University of Technology, Technological Sciences, Materials Engineering, T008),
Dr. Anca Ioana Stanculescu (National Institute of Materils Physics, Romania, Natural Sciences, Physics, N002),
Dr. Aurimas Vyšniauskas (Centre of Physical and Tecnological Sciences, Natural Sciences, Physics, N002).

The doctoral dissertation is available at the library of Kaunas University of Technology (Donelaičio 20, Kaunas).


The thesis is devoted to the complex study of newly synthesized organic electroactive compounds and their application in the efficient organic light emitting diodes (OLED). The aim of the work is to analyze the structure-properties relationship of organic semiconductors.
TADF is the emission of triplet up-conerted excitons. Enhancement of spin-orbit coupling induced by heavy metal particles is a key for electrophosorescnece (PhOLEDs). Additionally to these phenomena, ambipolarity and aggregation-induced emission enhancement (AIEE) were investigated.
Red non-doped OLEDs based on D-A-D emitters with a benzothiadiazole acceptor and carbazolyl donors were fabricated and characterized. The possibility of tuning the characteristics of TADF and AIEE by selection of dimtehyldihydroacridine, phenoxazine, carbazole and phenothiazine donating substituents in D-A-D benzonitrile derivatives was demonstrated. TADF emitters based on diphenylsulfone and dibenzothiohene derivatives with two di-tert-butyldimethyldihydroacridine substituents reached external quantum efficiency (EQE) of OLEDs up to 24.1%. Characterization of the triphenyltriazine substituted by tert-butylcarbazolyl moieties as TADF emitters was performed. The suitability of methoxycarbazolyl-disubstituted dibenzofurans as hosts for TADF OLEDs and PhOLEDs was demonstrated. TADF OLED based on diphenylsulfone-based D-A-D derivative reached 20.1% of EQE.

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