Charge Carrier Mobility in Poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine Composites with Electron Acceptor Molecules.

Polymer composites based on poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine (poly-TPD) with PCBM and copper(II) pyropheophorbide derivative (Cu-PP) were developed. In thin films of the poly-TPD and Cu-PP composites, the charge carrier mobility was investigated for the first time. In the ternary poly-TPD:PCBM:Cu-PP composite, the electron and hole mobilities are the most balanced compared to binary composites and the photoconductivity is enhanced due to the sensitization by Cu-PP in blue and red spectral ranges. The new composites are promising for use in the development of photodetectors.

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.

Photoconduction and Electroluminescence of Copper (II) Protoporphyrin and Chlorin Cu-C-e6.

Cu (II) protoporphyrin Cu-PP-IX and chlorin Cu-C-e6 were found to have both thin solid film formation and charge carrier transport abilities. In the layers deposited by resistive thermal evaporation, the mobilities of holes and electrons are on the order of 10-5 cm2 V-1 s-1. Organic light-emitting diodes incorporating the dye molecules as emitting dopants demonstrate electroluminescence in the UV and near-IR ranges.

New Unsymmetrically Substituted Benzothiadiazole-Based Luminophores: Synthesis, Optical, Electrochemical Studies, Charge Transport, and Electroluminescent Characteristics.

Three new benzothiadiazole (BTD)-containing luminophores with different configurations of aryl linkers have been prepared via Pd-catalyzed cross-coupling Suzuki and Buchwald-Hartwig reactions. Photophysical and electroluminescent properties of the compounds were investigated to estimate their potential for optoelectronic applications. All synthesized structures have sufficiently high quantum yields in film. The BTD with aryl bridged carbazole unit demonstrated the highest electrons and holes mobility in a series. OLED with light-emitting layer (EML) based on this compound exhibited the highest brightness, as well as current and luminous efficiency. The synthesized compounds are not only luminophores with a high photoluminescence quantum yield, but also active transport centers for charge carriers in EML of OLED devices.

Crystallography and Molecular Arrangement of Polymorphic Monolayer J-Aggregates of a Cyanine Dye: Multiangle Polarized Light Fluorescence Optical Microscopy Study.

The molecular orientation in monolayer J-aggregates of 3,3-di(γ-sulfopropyl)-5,5-dichlorotiamonomethinecyanine dye has been precisely estimated using improved linear polarization measurements in the fluorescence microscope in which a multiangle set of polarization data is obtained using sample rotation. The estimated molecular orientation supplemented with the previously established crystallographic constraints based on the analysis of the well-developed two-dimensional J-aggregate shapes unambiguously indicate the staircase type of molecular arrangement for striplike J-aggregates with the staircases oriented along strips. The molecular transition dipoles are inclined at an angle of ∼25° to the strip direction, whereas the characteristic strip vertex angle ∼45° is formed by the [100] and [1-10] directions of the monoclinic unit cell. Measurements of the geometry of partially unwound tubes and their polarization properties support the model of tube formation by close-packed helical winding of flexible monolayer strips. In the tubes, the long molecular axes are oriented at a small angle in the range of 5-15° to the normal to the tube axis providing low bending energy. At a nanoscale, high-resolution atomic force microscopy imaging of J-aggregate monolayers reveals a complex quasi-one-dimensional organization.

Polymorphism of Two-Dimensional Cyanine Dye J-Aggregates and Its Genesis: Fluorescence Microscopy and Atomic Force Microscopy Study.

Polymorphic J-aggregates of monomethine cyanine dye 3,3'-di(γ-sulfopropyl)-5,5'-dichlorotiamonomethinecyanine (TC) have been studied by fluorescence optical microscopy (FOM) and by atomic force microscopy (AFM). The in situ FOM observations in a solution drop distinguish two J-aggregate morphology classes: flexible strips and rigid rods. The AFM imaging of dried samples reveals a strong J-aggregate structural rearrangement under adsorption on a mica surface with the strips self-folding and the rods squashing into rectangular bilayers and much deeper destruction. In the present work, the following structural conclusions have been drawn on the basis of careful consideration of strip crystal habits and various structural features of squashed/destructed rods: (1) the tubular morphology of TC rods is directly proved by FOM measurements in the solution bulk; (2) the staircase model of molecular arrangement in strips is proposed explaining the characteristic ∼44° skew angle in strip vertices; (3) a model of tube formation by a close-packed helical winding of flexible monolayer strips is proposed and justified which explains the observed J-aggregate polymorphism and strip-to-rod polymorphic transformations in a wide spatiotemporal scale; (4) at a nanoscale, an unexpectedly complex quasi-one-dimensional organization in J-aggregate two-dimensional monolayers is observed by high-resolution AFM imaging of constituent nanostrips separated by a characteristic distance in the range of 6-10 nm. The obtained results indicate that the underlying monolayer structure is the same for all J-aggregate polymorphs.