Benzo[b]selenophene/thieno[3,2-b]indole-Based N,S,Se-Heteroacenes for Hole-Transporting Layers

Synthesis, Photo- and Electroluminescence of New Polyfluorene Copolymers Containing Dicyanostilbene and 9,10-Dicyanophenanthrene in the Main Chain

Using palladium-catalyzed Suzuki polycondensation, we synthesized new light-emitting fluorene copolymers containing the dicyano derivatives of stilbene and phenanthrene and characterized them by gel permeation chromatography, UV-vis absorption spectroscopy, spectrofluorimetry, and cyclic voltammetry. The photoluminescence spectra of the synthesized polymers show significant energy transfer from the fluorene segments to the dicyanostilbene and 9,10-dicyanophenanthrene units, which is in agreement with the data of theoretical calculations. OLEDs based on these polymers were fabricated with an ITO/PEDOT-PSS (35 nm)/p-TPD (30 nm)/PVK (5 nm)/light emitting layer (70-75 nm)/PF-PO (20 nm)/LiF (1 nm)/Al (80 nm) configuration. Examination of their electroluminescence revealed that copolymers of fluorene with dicyanostilbene show yellow-green luminescence, while polymers with 9,10-dicyanophenanthrene have a greenish-blue emission. The 9,10-dicyanophenanthrene units have a more rigid structure compared to dicyanostilbene and, in OLEDs based on them, an increase in maximum brightness is observed with an increase in the content of the additive to the polymer chain. In particular, the device using fluorene copolymer with 9,10-dicyanophenanthrene (2.5 mol%) exhibited a maximum brightness of 9230 cd/m2 and a maximum current efficiency of 3.33 cd/A.

Copper(II) Etioporphyrinate as a Promising Photoluminescent and Electroluminescent Temperature Sensor

Luminescent temperature sensors are of great interest because they allow remote determination of temperature in transparent media, such as living tissues, as well as on scattering or transparent surfaces of materials. This study analyzes the luminescent properties of copper(II) etioporphyrinate (Cu-EtioP) in a polystyrene film upon variation of temperature from −195 °C to +65 °C in a cryostat. It is shown that the ratio of intensities of phosphorescence transitions in the red spectral region of such a material varies significantly, that is, the material has thermosensory properties. The phosphorescence decay curves of copper(II) etioporphyrinate in a polystyrene film are analyzed. The quantum yield of phosphorescence of copper(II) etioporphyrinate determined by the absolute method was 3.15%. It was also found that the electroluminescence (EL) spectra of copper(II) etioporphyrinate in a poly(9-vinylcarbazole) (PVK) matrix demonstrated a similar change in the spectra in the temperature range −3 °C to +80 °C. That is, copper(II) etioporphyrinate can also be used as a luminescent temperature sensor as part of an active OLED layer.

The effect of PbS quantum dots on molecular dynamics and conductivity of PTB7:PC71BM bulk heterojunction as revealed by dielectric spectroscopy

A ternary photovoltaic blend containing the PTB7 donor component, the PC71BM acceptor component, and colloidal quantum dots of lead sulfide (PbS QDs) was investigated using broadband dielectric spectroscopy. In the dielectric loss spectrum of PTB7:PC71BM:PbS QDs, γ- and β-relaxation processes in PTB7 were recognized and analyzed in terms of Arrhenius-type equations. To elucidate the effect of PbS QDs on molecular dynamics of PTB7, the activation energies of both processes were evaluated and compared with those obtained for the binary PTB7:PC71BM blend. Using the CELIV method, the charge carrier mobility was estimated. The PbS QD incorporation into the binary blend was shown to decrease both electron and hole mobility in the ternary PTB7:PC71BM:PbS QD blend. For evaluating the charge carrier lifetime in the ternary blend, the Cole-Cole diagrams derived from the dc conductivity data were plotted. The charge carrier lifetime was found to be much less than the hole extraction time, thus providing effective accumulation of charge carries at the electrodes in the ternary blend under investigation.

Copper(II) meso-Tetraphenyl- and meso-Tetrafluorenyl Porphyrinates as Charge Carrier Transporting and Electroluminescent Compounds

Studies on copper(II) tetrafluorenyl porphyrinate (CuTFP) and copper(II) tetraphenyl porphyrinate (CuTPP) have been focused on the charge carrier transport in their solid films and electroluminescence of their composites. In the dye layers deposited by resistive thermal evaporation, the mobilities of holes and electrons are on the order of 10^-5 and 10^-6 cm² V^-1 s^-1 for the charge transport under the influence of traps, and the charge mobility reaches the order of 10^-3 cm² V^-1 s^-1 at space-charge-limited current in the nontrapping mode. For the dye molecules, the correlation between the mobility of charge carriers and the distribution of the electron density on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), which serve as hopping sites for holes and electrons, respectively, is considered. Organic light-emitting diodes incorporating the dye molecules as emitting dopants demonstrate electroluminescence in the near-infrared (IR) range.

An Approach to the Construction of Benzofuran-thieno[3,2-b]indole-Cored N,O,S-Heteroacenes Using Fischer Indolization

A series of 6H-benzofuro[2',3':4,5]thieno[3,2-b]indoles were readily synthesized from methyl 3-aminothieno[3,2-b]benzofuran-2-carboxylates using a one-pot procedure with Fischer indolization as the key step. At the same time, 3-aminothieno[3,2-b]benzofuran-2-carboxylates were prepared from 3-chlorobenzofuran-2-carbaldehydes in three steps, including replacement of the Cl atom at the C-3 position of these starting substrates onto the -SCH2CO2Me moiety, conversion of the CHO group at the C-2 position into the CN group, followed by base-promoted cyclization of the formed carbonitrile. The present route was elaborated by us because we failed to obtain directly the desired 3-aminothiophene-2-carboxylate by reaction of 3-chlorobenzofuran-2-carbonitrile with methyl thioglycolate in the presence of various bases. In turn, 3-chlorobenzofuran-2-carbaldehydes were prepared from benzofuran-3(2H)-ones following the Vilsmeier-Haack-Arnold reaction.

An Effective Route to Dithieno[3,2-b:2′,3′-d]thiophene-Based Hexaheteroacenes

A series of 12H-[1]benzo[4′′,5′′]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]indoles were efficiently prepared in three steps starting from available benzo[b]thieno[2,3-d]thiophen-3(2H)-ones. These fused ketones were treated with the Vilsmeier reagent and hydroxylamine hydrochloride to give the corresponding 3-chlorobenzo[b]thieno[2,3-d]thiophene-2-carbonitriles, which then reacted with methyl sulfanylacetate to form methyl 3-aminobenzo[4′,5′]thieno[2′,3′:4,5]thieno[3,2-b]thiophene-2-carboxylates, in accordance with the Fiesselmann thiophene synthesis protocol. Finally, the desired N,S-heterohexacenes were obtained by conversion of these fused 3-aminothiophene-2-carboxylates into the corresponding 3-aminothiophene intermediates, which acted as synthetic equivalents of thiophen-3(2H)-ones, followed by their acid-promoted reaction with arylhydrazines, in accordance with the Fischer indolization procedure.