Abstract
Due to their luminescent and charge-transport properties, polyfluorenes and their copolymers find wide application in optoelectronics as light-emitting and photoactive materials. For use in optoelectronic devices, particularly organic light-emitting diodes (OLEDs), it is necessary to ensure a sufficiently high and balanced mobility of electrons and holes injected into the light-emitting polymer layer. To achieve this, electron-acceptor units must be introduced into the polyfluorene structure to facilitate electron transport between molecules, as the electron conductivity of polyfluorenes is significantly lower than their hole conductivity. In this study, a series of copolyfluorenes with dicyanostilbene and phenanthrene-9,10-dicarbonitrile moieties were prepared via polycondensation via the Suzuki reaction mechanism. For OLEDs with these copolyfluorenes as light-emitting material, the highest electroluminescence brightness (11000 cd/m2) and the lowest turn-on voltage (3.1 V) were achieved. To create a chemosensor for β-lactamase secreted by tuberculosis patients, a cephalosporin moiety was introduced into the end group of copolyfluorene containing 2.5 mol% dicyanostilbene. It has been shown that cleavage of the cephalosporin fragment by β-lactamase leads to a change in the photoluminescence spectrum with a shift to the yellow region. A simplified in situ method for producing TADF polymers has been developed, in which TADF-active tricarbazole-triazine fragments are formed directly during polymer chain growth. The method is based on Suzuki polycondensation using readily available monomers that do not exhibit TADF properties individually. The use of the stable PEPPSI-IPr catalyst allowed for open-air synthesis, eliminating the need for an inert atmosphere. The inclusion of bis(4-bromobenzyl)dimethylsilane in the polymer ensured high solubility in toluene and chlorobenzene and significantly increased the material's resistance to concentration quenching—luminescence remains stable up to 50 wt% doping (unlike its silicon-free counterpart, where quenching begins at 10 wt%). The resulting polymer is characterized by a small singlet-triplet splitting of ΔEST = 0.045 eV, a photoluminescence quantum yield of 30%, and a delayed component lifetime of 2.3 μs. OLED devices created on the basis of this polymer demonstrate a maximum brightness of 4000 cd/m2, an external quantum yield of 13%, and an electroluminescence peak at 500 nm.