Highly fluorescent organic nanoparticles, films and crystals for sensing and lasing applications

In this work the photophysical properties of novel phenylenediacetonitrile (PDACN) derivatives bearing systematically introduced different side-groups are investigated in their different forms (liquid and solid solution, neat films and nanoparticles). It was determined that emission properties can be tuned in a controlled manner by changing film/nanoparticle morphology by varying preparation conditions or altering molecular structure. Demonstrated tunability of fluorescence spectra and intensity via induced changes in morphology encourages technological application of PDACN compounds in threshold temperature or volatile organic vapour fluorescence sensing. Although organic materials expressing efficient fluorescence and high radiative decay rates have been of interest as a gain medium in lasing applications for a few last decades, no systematic studies of amplified spontaneous emission (ASE) concentration behaviour in such a wide concentration range (0.1 – 100%) were carried out so far. Thorough assessment of concentration effects on ASE properties of new fluorene- and benzo[c]fluorene-cored oligomers allowed to achieve extremely low ASE thresholds at very high compound concentrations and in the neat amorphous films, which are required for future organic laser applications. Moreover, new bifluorene derivatives bearing different linking groups were inspected as building materials for highly fluorescent organic single crystals, attractive for electrically pumped laser applications. Control of intermolecular interactions, achieved by chemical structure design, allowed to demonstrate record low ASE threshold values (700 W/cm2) in organic single crystals grown by physical vapour transport

Našiai fluorescuojantys organiniai nanodariniai, sluoksniai ir kristalai taikymams jutikliuose ir lazeriuose

In this work the photophysical properties of novel phenylenediacetonitrile (PDACN) derivatives bearing systematically introduced different side-groups are investigated in their different forms (liquid and solid solution, neat films and nanoparticles). It was determined that emission properties can be tuned in a controlled manner by changing film/nanoparticle morphology by varying preparation conditions or altering molecular structure. Demonstrated tunability of fluorescence spectra and intensity via induced changes in morphology encourages technological application of PDACN compounds in threshold temperature or volatile organic vapour fluorescence sensing. Although organic materials expressing efficient fluorescence and high radiative decay rates have been of interest as a gain medium in lasing applications for a few last decades, no systematic studies of amplified spontaneous emission (ASE) concentration behaviour in such a wide concentration range (0.1 – 100%) were carried out so far. Thorough assessment of concentration effects on ASE properties of new fluorene- and benzo[c]fluorene-cored oligomers allowed to achieve extremely low ASE thresholds at very high compound concentrations and in the neat amorphous films, which are required for future organic laser applications. Moreover, new bifluorene derivatives bearing different linking groups were inspected as building materials for highly fluorescent organic single crystals, attractive for electrically pumped laser applications. Control of intermolecular interactions, achieved by chemical structure design, allowed to demonstrate record low ASE threshold values (700 W/cm2) in organic single crystals grown by physical vapour transport

Diboraanthracene-doped polymer systems for colour-tuneable room-temperature organic afterglow

Organic ultralong room temperature phosphorescence (RTP), or organic afterglow, is a unique phenomenon, gaining widespread attention due to its far-reaching application potential and fundamental interest. Here, two laterally expanded 9,10-dimesityl-dihydro-9,10-diboraanthracene (DBA) derivatives are demonstrated as excellent afterglow materials for red and blue-green light emission, which is traced back to persistent thermally activated delayed fluorescence and RTP. The lateral substitution of polycyclic DBA scaffold, together with weak transversal electron-donating mesityl groups, ensures the optimal molecular properties for (reverse) intersystem crossing and long-lived triplet states in a rigid poly(methyl methacrylate) matrix. The achieved afterglow emission quantum yields of up to 3 % and 15 %, afterglow lifetimes up to 0.8 s and 3.2 s and afterglow durations up to 5 s and 25 s (for red and blue-green emitters, respectively) are attributed to the properties of single molecules

Efficient p-phenylene based OLEDs with mixed interfacial exciplex emission

Organic electronics, mainly due to the advancement of OLED (Organic Light Emitting Diode) technology, is a fast developing research area, and has already revolutionized the displays market. This direction presents the use of exciplex emitters and thermally activated delayed fluorescence (TADF) in OLEDs. This is shown through electrochemical characterisation of six p-phenylene derivatives for application in optoelectronic devices and presents the possibility the compounds' use as OLED emitters. In these OLED devices, it is established that selenophene based compounds with a "heavy-atom effect" can be used as potential emitters when exciplex phenomena are involved. (C) 2015 Elsevier Ltd. All rights reserved

TADF parameters in the solid state: an easy way to draw wrong conclusions

The successful development of thermally activated delayed fluorescence (TADF) OLEDs relies on advances in molecular design. To guide the molecular design toward compounds with preferable properties, special care should be taken while estimating the parameters of prompt and delayed fluorescence. Mistakes made in the initial steps of analysis may lead to completely misleading conclusions. Here we show that inaccuracies usually are introduced in the very first steps while estimating the solid-state prompt and delayed fluorescence quantum yields, resulting in an overestimation of prompt fluorescence (PF) parameters and a subsequent underestimation of the delayed emission (DF) yield and rates. As a solution to the problem, a working example of a more sophisticated analysis is provided, stressing the importance of in-depth research of emission properties in both oxygen-saturated and oxygen-free surroundings

Realization of deep-blue TADF in sterically controlled naphthyridines for vacuum- and solution-processed OLEDs

Narrow-band deep-blue (emission peak 80 nm) sky-blue (λmax ≈ 480 nm) emission. The demonstrated emitters are among the best-performing conventional D–A-type blue/deep-blue TADF emitters in terms of EQE and efficiency roll-off properties of their devices