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Four donor-acceptor-donor compounds consisting of 9,9-dimethyl-9,10-dihydroacridine donors differently linked to a benzothiadiazole acceptor were designed using DFT calculations and synthesized, namely 4,7-bis(4-(9,9-dimethyl-9,10-dihydroacridine)phenyl)benzo[c][1,2,5]thiadiazole (1), 4,7-bis(2,5-dimethyl-4-(9,9-dimethyl-9,10-dihydroacridine)phenyl)benzo[c][1,2,5]thiadiazole (2), 4,7-bis(3,5-di(9,9-dimethyl-9,10-dihydroacridine)phenyl)benzo[c][1,2,5]thiadiazole (3), and 4-(3,5-di(9,9-dimethyl-9,10-dihydroacridine)phenyl)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (4). As predicted theoretically, all studied compounds were electrochemically active both in the reduction as well as in the oxidation modes. They underwent one electron quasi-reversible reduction. Oxidation of 1 and 2 involved a two electron process transforming them into dications and carrying out, in parallel, their dimerization. Oxidation of 3 and 4 resulted in their oligomerization (polymerization). The electrochemically determined ionisation potentials (IP) of 1-4 were similar, covering a narrow range of 5.28-5.33 eV and were consistent with DFT calculations. Larger differences were found for experimentally determined electron affinity (EA) values, being significantly lower for 2 (|EA| = 2.59 eV) as compared to 1, 3 and 4 whose |EA| values were higher by 0.15-0.25 eV, again consistent with DFT calculations. DFT calculations predict positive values of ΔE(S1-T1) for all compounds i.e. in the range of 0.18 eV to 0.43 eV for 1, 3 and 4 and a significantly lower value for 2 (0.06 eV), indicating a possible RISC process in this case. DFT calculations of ΔE(S1-T2) lead to negative and very small values for 2-4 implying a possible involvement of higher lying triplets in the generation of singlet excitons. The investigated derivatives exhibited fluorescence in the orange-red spectral range (550-770 nm) and were strongly dependent on the solvent polarity. The highest PLQY value of 37% was measured for 1 in toluene. The PLQY values significantly improved upon deoxygenation of the studied solutions. Solid state samples also exhibited higher PLQY values as compared to those determined for DCM solutions. These findings were rationalized by partial suppression of the vibrationally induced emission quenching in the solid state due to the intermolecular interaction confinement. [ABSTRACT FROM AUTHOR]

The overwhelming majority of efficient organic light‐emitting diodes (OLEDs) are based on amorphous emitting layers. The devices with crystalline emitters usually show significantly worse performance. It is demonstrated that controlled thermal treatments of phenoxazine‐substituted acridones may lead to a spectacular improvement of photo‐ and electroluminescence of these luminophores. The three acridone derivatives studied, namely 2‐phenoxazine‐N‐hexylacridone (PHhA), 2,7‐bis‐(phenoxazine)‐N‐hexylacridone (bPHhA), and 2,7‐bis[3‐(phenoxazine)phenyl]‐N‐hexylacridone (PHPhhA), are characterized by relatively narrow photoluminescence spectra and photoluminescence quantum yields approaching 100%. These spectra can be reversibly tuned through appropriate thermal treatment of the deposited layers, undergoing shifts up to 92 nm upon transformation from amorphous to crystalline states. Strong thermally activated delayed fluorescence (TADF) observed for these compounds is manifested by a significantly higher reverse intersystem crossing rate of 1.92×106 s−1 as compared to the intersystem crossing rate of 5.68×105 s−1. These improvements are attributed to the annealing‐induced conformational equilibration due to crystallisation in combination with hosting. Adequacy of the proposed concept is demonstrated by the fabrication of devices exhibiting external quantum efficiencies reaching 20.7% – a record value for OLEDs with crystalline emitting layers. The presented approach of annealing‐induced conformational equilibration can lead to improved TADF properties for other fluorescent organic emitters presently considered inefficient. [ABSTRACT FROM AUTHOR]

Poly(3,3'-dioctyl-2,2':5',2'-terthiophene) is fabricated into five fractions distinctly differing in their molecular weights in order to determine the influence of the degree of polymerization (D[P.sub.n]) on its principal physicochemical parameters. The results have shown that at least in the polythiophene family of electroactive parameters, the DP dependence of the crucial electrical parameters persists to relatively high molecular weights and have indicated the importance of the macromolecular parameters control in the fabrication of polymer-based electronic and electrochemical devices.

The grafting of an electoactive oligomer from the polyaniline family-aniline tetramer-on CdSe nanocrystals after their functionalization with 4-formyldithiobenzoic acid is discussed. A simple synthesis method allows for the design of new ligands, and facilites the grafting of other molecules and macromolecules, such as conjugated oligomers or polymers.

Starting from simple metal precursors (AgNO3 and InCl3), ligands (oleylamine (OLA) and 1-dodecanethiol (DDT)) and popular sulfur precursor S/OLA, we have developed a new method for the preparation of colloidal Ag2S nanocrystals and highly luminescent ternary AgInS2 nanocrystals. The significant advantage of this method is that the nanocrystals can be prepared at room temperature in an ultrasonic bath, without the need for an inert gas atmosphere. In particular, using this method, it was possible to perform the synthesis of the studied nanocrystals in an NMR tube providing direct analytical access to chemical transformations occurring in the reaction mixture during the nanocrystal synthesis. Detailed analysis of the evolution of NMR signals originating from ligands (OLA and DDT) enabled us to identify the nucleation and growth stages as well as the stabilization stage of the nanocrystal formation i.e. the stage in which the ligands were permanently attached to the nanocrystal surface. We also demonstrated that under the analyzed conditions, the reactivities of silver and indium precursors resulting in appropriate cation-to-ligand connections (Ag+–DDT and In3+–OLA) were crucial for the nucleation of ternary AgInS2 nanocrystals exhibiting intense red luminescence. [ABSTRACT FROM AUTHOR]