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Thermally activated delayed fluorescence has been found in a group of tricarbazolylamines that are purely electron-donating, non-charge-transfer (CT) molecules. We show that the reverse intersystem crossing step in these materials is mediated through upper triplet states. Reverse internal conversion is shown to be the thermally activated mechanism behind the triplet harvesting mechanism. The strongly mixed n−π*/π–π* character of the lowest energy optical transitions retains high oscillator strength and gives rise to high ΦPL. Organic light-emitting diode devices using these materials were fabricated to show very narrow (full width at half-maximum = 38–41 nm) electroluminescence spectra, clearly demonstrating the excitonic nature of the excited states. This new combination of physicochemical properties of a non-CT molecule yields thermally activated delayed fluorescence, but via a different, physical mechanism, reverse internal conversion delayed fluorescence.

In this work the electrochemical and spectroelectrochemical characterization of a s-tetrazine-triphenylamine derivative with a donor–acceptor–donor-type structure is reported, which in addition undergoes electrochemical polymerization. The investigations of the polymerized layers have revealed unusual characteristics. Thin polymeric film exhibits charge-trapping properties with great storage and memory effect. Moreover, the polymer displays reversible switching of fluorescence in oxidation mode and emission of light during reduction.

Organic electronics, mainly due to advancements in OLED (organic light-emitting diode) technology, is a fast developing research area having already revolutionized the displays market. This direction presents the use of exciplex emitters and thermally activated delayed fluorescence (TADF) in OLEDs, to give efficient, stable emitters that do not use scarce and expensive materials such as iridium. Here, it is shown for the first time several diketopyrrolopyrrole (DPP) derivatives that could be used as emitters in OLED devices. We were able to improve the efficiency of DPP materials by forming exciplex-enhanced OLED devices. These organic materials were also characterized by electrochemical and spectroscopic methods in order to elucidate each molecule's interaction and decrease the photoluminescence efficiency.

Here we report the characterization of diquinoline derivatives with ambipolar character. The investigated derivatives show low p- and moderately low n-doping redox systems. The derivatives were investigated and the electrochemical and optical properties of these compounds measured, with attempts to correlate the properties with their π-electron conjugation lengths. We showed the marked influence of the heteroatom in the bridge (central ring) and geometry of the molecule with its electronic properties. The compounds were compared by UV–vis–NIR and electron paramagnetic resonance (EPR) spectroelectrochemistry indicating very different charge and spin properties dependent on the heteroatoms present. Finally the organic light-emitting diode (OLED) devices were formed and characterized.

Electrochemical and spectroelectrochemical properties of a series of new penta-ring donor–acceptor compounds, comprising 1,3,4-oxadiazole, 1,3,4-thiadiazole, and 1,2,4-triazole central ring, symmetrically connected to substituted bithiophenes, were investigated. Aromaticity and electrophilic–nucleophilic traits of the aza-heterocyclic units, fostering inductive and resonance effects that translate to conjugation enhancement and electron (de)localization, were found a major factor determining the key electron properties of ionization potential (IP) and electron affinity (EA) of these molecules. Replacing the alkyl thiophene substituent for an alkoxy one afforded certain control over the two parameters as well. All studied compounds were found to undergo electrochemical polymerization giving p- and n-dopable products, featuring good electrochemical reversibility of their oxidative doping process, as demonstrated by cyclic voltammetry and UV–vis–NIR, EPR spectroelectrochemistry. While electropolymerization o...