In this letter, we investigate electronic structures and electron-injection mechanisms of the effective cathode structures for organic light-emitting devices incorporating cesium carbonate ͑Cs 2 CO 3 ͒, either deposited as an individual thin injection layer or doped into the organic electron-transport layers. The electronic structures and the interface chemistry studied by ultraviolet and x-ray photoemission spectroscopy show that the enhanced electron injection is associated with strong n-doping effects and increase of electron concentrations in the electron-transport layer induced by Cs 2 CO 3. Since such a reaction occurs without the presence of metals, cathode structures incorporating Cs 2 CO 3 may be applied to a wide range of electrode materials.

A new dye, SSD1, featuring two donor/acceptor chromophores aligned in a spiro configuration with two anchoring groups separated at a distance of 10.05 A (closely matching the distance between the adsorption sites of the anatase TiO(2) surface) undergoes efficient dye adherence on TiO(2) films. A dye-sensitized solar cell incorporating SSD1 exhibited a short-circuit current of 8.9 mA cm(-2), an open-circuit voltage of 0.63 V, a fill factor of 0.67, and a power conversion efficiency of 3.75%.

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A novel ambipolar spiro-configured D-A blue-light emitter bearing hole-transporting diphenylamino groups and electron-transporting phenylbenzimidazole groups was synthesized, characterized, and incorporated into an efficient single-layer organic light-emitting diode (OLED) device exhibiting blue-emission Commission International d'Eclairage (CIE) coordinates of 0.15 and 0.14, a turn-on potential of 4 V, a maximum brightness of 2800 cd/m2 at 830 mA/cm2 (19 V), and a maximum quantum efficiency of 0.53% (0.61 cd/A).

All-conjugated "rod−rod" diblock copolymers are an emerging class of polymeric materials of considerable interest for applications in chemical and biological sensors or as components for optoelectronic devices. Here, we report a novel cationic diblock copolymer containing a neutral polyalkylfluorene block covalently bound to a polar polyfluorene counterpart poly[9,9-bis(6-trimethylammoniumhexyl)-2,7-fluorene]-b-poly(3hexyl-2,5-thiophene) (PF6NBr-b-PF8)which was synthesized in a sequential Suzuki−Miyaura polymerization and was made ionic with trimethylamine in a subsequent quaternization step. The optical properties of this material were investigated by UV/ vis and photoluminescence spectroscopies in three different solvents: methanol, THF and THF/methanol 1:1. Atomic force microscopic (AFM) imaging experiments provided evidence for solvent-induced aggregation. The formation of vesicles and spherical particles is observed in layers from THF and methanolic solution.

The electrochemical polymerization conditions for the synthesis of spirobifluorene-based polymer (EF-CN1) films with adequate properties to be applied in an organic light emitting diode (OLED) were studied. We demonstrate that, after optimization in the parameters of electrochemical polymerization, we were able to obtain a conducting polymeric film with very smooth surface, absence of pinholes, and high optoelectronic activity, which was compatible as an efficient hole transporting layer in OLED. The electrochemical deposited polymers, and polymer films obtained through drop casting from solution of chemically synthesized polymer (C-CN1), were characterized and the results compared. The films were studied by cyclic voltammetry, UV–vis, fluorescence spectra, scanning electron mictroscopy, and atomic force microscopy. The built OLEDs achieve current-luminous efficiency and external quantum efficiency of 2.6 cd/A and 0.50%, respectively.

We have synthesized and characterized a novel thermally polymerizable triaryldiamine monomer (VB-FNPD) possessing a styrene-functionalized 9,9-diarylfluorene core and have used time-of-flight transient photocurrent techniques to investigate the hole transport properties of its solution-processed and subsequently thermally cured (170 C) polymer films. This novel polymeric material exhibits nondispersive hole transport behavior with a high hole drift mobility (up to 10 À4 cm 2 V À1 s À1 ). The film displayed remarkable ambient stability, even when exposed to air for one month. We tested the thermally generated polymer film as a hole transport material in organic light-emitting diodes incorporating tris(8-hydroxyquinolate) aluminium (Alq 3 ) as the emission and electron transport layer. The device exhibited a maximum external quantum efficiency (h ex ) of 1.4%, significantly better than that of the device prepared using the corresponding model compound VB-model (h ex ¼ 1.1%).

Hole mobilities of up to 2 × 10 -3 cm 2 V -1 s -1 of 2,7-and 2,2′-disubstituted spirobifluorene-based triaryldiamine derivatives have been measured using time-of-flight (TOF) techniques. Among these derivatives, 27DPSF (possessing diphenylamino groups attached onto the same biphenyl branch of spirobifluorene) and 22DPASF (possessing extended π-conjugation of the chromophore) exhibited the highest hole mobilities because of their greater intermolecular interactions. The charge transport parameters were extracted, using a Gaussian disorder model (GDM), from detailed temperature-and field-dependent hole mobility measurements. For 2,2′-disubstituted systems possessing different diarylamino groups, the hole mobilities decreased in the order 22DPSF > 22DTSF > 22DBPSF, indicating that spatial hindrance had a crucial effect on the hole transport behavior. To verify these disubstituted spirobifluorene-based amines can be used as HTLs in OLED devices. A standard device was fabricated with the configuration ITO/m-MTDATA (20 nm)/triaryldiamine derivative (40 nm)/Alq 3 (60 nm)/LiF (0.5 nm)/Al (150 nm), which gave a relatively high current density (ca. 5200 mA/cm 2 ), impressive maximum brightness (1.3 × 10 5 cd/m 2 ), and high external quantum efficiency (1.8%). The device performances are strongly correlated to the charge transporting behavior of such disubstituted spirobifluorene-based amines.