Synthesis and properties of dimeric naphthalene diimides

New dimeric naphthalene diimides were synthesized via condensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride with different aromatic amines such as 2-amino-4-tert-amylphenol and 4-tert-butylcyclohexylamine as well as using linking agents such as hydrazine and p-phenylenediamine. The unsymmetrical imide synthesis approach was used to prepare intermediate derivatives. The structures of the compounds were characterized by means of H-1 NMR, IR and mass spectrometry. The thermal behavior of the naphthalene diimides was investigated via differential scanning calorimetry. The studies showed that the compounds prepared are amorphous materials with glass transition temperatures from 132 degrees C to 266 degrees C. Optical properties of the synthesised naphthalene diimides in solution were studied by UV spectroscopy. All the compounds absorb electromagnetic radiation in the range of 200-400 nmVytauto Didžiojo universitetasŽemės ūkio akademij

Star-shaped triphenylamine-based molecular glass for solid state dye sensitized solar cell application

International audienceThe synthesis by Suzuki cross-coupling and properties of a glass-forming star-shaped compound tris(9-(3-methylphenyl)carbazol-3-yl)-triphenylamine are reported. The thermal, optical, photoelectrical and electrochemical properties of the hole-transporting compound were studied by differencial scanning calorimetry, thermogravimetric analysis, UV/vis spectroscopy, electron photoemission, time-of-flight technique and cyclic voltammetry. The compound exhibits high thermal stability with a the temperature of the onset of the thermal degradation of 510 °C. The compound absorbs in 200-400 nm range and possesses an optical band gap of 3.15 eV, avoiding any screening effect with the dye. The solid state ionization potential (IPss) of the molecule, measured by electron photoemission and cyclic voltammetry is around 5 eV similar to the standard spiroOMeTAD hole-transporting material. The hole drift mobility in the amorphous layer of reported compound reach 6.4 × 10−5 cm2/Vs under high electrical field (6.4 × 105 V/cm). This synthesized derivative was finally assessed as hole transporting material in the solid state dye-senstized solar cells with (5-(1,2,3,3a,4,8b-hexahydro-4-[4-(2,2-diphenylvinyl)phenyl]-cyclopeanta[b]indole-7-ylmethylene)-4-oxo-2-thioxo-thiazolidin-3-yl)acetic acid (D102) as sensitizer and showed a power conversion efficiency of 0.63% under standard solar irradiation (100 mW/cm2, AM1.5

Not the Sum of their Parts: Understanding Multi-Donor Interactions in Symmetric and Asymmetric TADF Emitters

A pair of thermally activated delayed fluorescence (TADF) emitters with symmetric and asymmetric D-A-D structure are investigated. Despite displaying near-identical photoluminescence spectrum and quantum yields, the symmetric material possesses significantly better delayed fluorescence characteristics and OLED performance. Building on a previous study of analogous D-A materials we are able to explain these differences in terms of different strengths of electronic interactions between the two donor units. This interaction lowers the energy of the TADF-active triplet state in the asymmetric molecule, increasing its singlet–triplet energy gap and leading to worse performance. This result therefore demonstrates a new strategy to selectively control the triplet states of TADF molecules, in contrast to established control of singlet states using host environment. These results also show that multi-donor TADF emitters cannot be understood simply as the sum of their isolated parts; these parts have different electronic interactions depending on their relative positions, even when there is no scope for steric interaction

Not the sum of their parts : understanding multi-donor interactions in symmetric and asymmetric TADF emitters

A pair of thermally activated delayed fluorescence (TADF) emitters with symmetric and asymmetric D-A-D structure are investigated. Despite displaying near-identical photoluminescence spectrum and quantum yields, the symmetric material possesses significantly better delayed fluorescence characteristics and OLED performance. Building on a previous study of analogous D-A materials we are able to explain these differences in terms of different strengths of electronic interactions between the two donor units. This interaction lowers the energy of the TADF-active triplet state in the asymmetric molecule, increasing its singlet-triplet energy gap and leading to worse performance. This result therefore demonstrates a new strategy to selectively control the triplet states of TADF molecules, in contrast to established control of singlet states using host environment. These results also show that multi-donor TADF emitters cannot be understood simply as the sum of their isolated parts; these parts have different electronic interactions depending on their relative positions, even when there is no scope for steric interaction