Sermet Koyuncu

Electrochromic and electroluminescent devices based on a novel branched quasi-dendric fluorene-carbazole-2,5-bis(2-thienyl)-1H-pyrrole system

We report here the synthesis of a novel branched quasi-dendric system, 9,9′-(9,9′-dihexylfluorene-2,7-diyl)bis[3,6-bis(2,5-bis(2-thienyl)pyrrol-1-yl)carbazole], (FCSNS), in four steps, followed by coating onto an ITO-coated glass surface by an electropolymerization process to give a very stable cross-linked polymeric film (poly-FCSNS). The yellowish-green color of this film in its neutral state changed reversibly to black upon oxidation. An electrochromic device, assembled in the sandwich configuration [ITO/anodically coloring polymer (poly-FCSNS)//gel electrolyte//cathodically coloring polymer/(PEDOT)/ITO], exhibited a relatively short response time (about 1 s), a high redox stability, and a high coloration efficiency (1624 cm2C−1). In addition to electrochromic studies, organic light-emitting diode (OLED) work was also carried out using FCSNS. A multilayer OLED having a configuration of ITO/PEDOT:PSS/FCSNS/Alq3/LiF : Al was fabricated, and it showed a turn-on voltage of approximately 6 V and exhibited a bright green emission with a luminance of 3700 cd m−2. The maximum luminous efficiency was found to be 2.0 cd A−1 at 14 V and 11.75 mA cm−2. The emitted light from the OLED device is green, and has the color coordinates of (x, y) (0.33, 0.54) according to CIE. Electrochemical and optical properties were also studied by using cyclic voltammetry, UV-Vis absorption and fluorescence spectroscopy, respectively.

Solution processable neutral state colourless electrochromic devices: effect of the layer thickness on the electrochromic performance

In this study, a neutral state colourless electrochromic device fabricated through a solution process is introduced. The device contains indium doped transparent oxide coated glass as the transparent conductive electrode, poly(N-(2-ethylhexyl)carbazol-3,6-diyl) (PCbz) as the anodically colouring material, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the ion storage layer and a lithium perchlorate based conducting gel electrolyte. A maximum optical contrast (ΔT%) of 58% at 800 nm is achieved by optimizing the film thickness of both the organic layers. The device that has layers of 220 nm PCbz and 120 nm PEDOT:PSS thickness revealed a high coloration efficiency (1246 cm2 C−1) and colouring and bleaching response times of 5.6 s and 2.3 s, respectively.

A novel complementary absorbing donor–acceptor pair in block copolymers based on single material organic photovoltaics

We report on the first synthesis of a highly crystalline donor–acceptor low band gap block copolymer by using diketopyrrolopyrrole (DPP) as a low band gap block and perylenebisimide (PDI) as a strong acceptor block. All important prerequisites for PV applications such as strong and broad optical absorption, compatible HOMO–LUMO levels can be accomplished and combined on one macromolecule at the same time. Besides, microphase separation is achieved by solvent annealing the film in dichloromethane and the PV performance is improved from 0.25% to 0.89%. The morphology and performance of this single component system can be enhanced by further improvements under processing conditions.

Synthesis and Characterization of Oligo-Salicylidene-3-Amino-1, 2, 4-Triazole and Oligo-2-Hydroxy Naphthalidene-3-Amino-1, 2, 4-Triazole

Abstract: In this study, the oxidative polycondensation reaction conditions of oligo-salicylidene-3-amino-1, 2, 4-triazole (OSAT) and oligo-2-hydroxy naphthalidene-3-amino-1, 2, 4-triazole (OHNAT) with air O2, H2O2, and NaOCl were studied in an aqueous alkaline medium at 80°C. The oligo-salicylidene-3-amino-1, 2, 4-triazole and oligo-2-hydroxy naphthalidene-3-amino-1, 2, 4-triazole were characterized by 1H-nuclear magnetic resonance (NMR), Fourier transform-infrared (FT-IR), ultraviolet-visible spectrometry (UV-Vis), size exclusion chromatography (SEC), and elemental analysis techniques. According to the SEC analysis, the number average–molecular weight (Mn), weight average–molecular weight (Mw), and polydispersity index (PDI) values of OSAT and OHNAT were found to be 1980 g mol−1, 5115 g mol−1, and 2.58 and 1752 g mol−1, 4300 g mol−1, and 2.45, respectively. Also, thermogravimetric (TG) analyses were shown to be unstable for oligo-salicylidene-3-amino-1, 2, 4-triazole and oligo-2-hydroxy naphthalidene-3-amino-1, 2, 4-triazole against thermo-oxidative decomposition. The weight losses of OSAT and OHNAT were found to be 97.30% and 98.48% at 900°C, respectively.

Synthesis, Characterization, and Thermal Properties of Oligo-2-Hydroxyphenylbenzaldimine

Abstract In this study, the oxidative polycondensation reaction conditions of 2-hydroxyphenylbenzaldimine (HPBA) with air oxygen and NaOCl were studied in an aqeous alkaline medium between 50 and 90°C. The product was characterized by 1H-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC), and element analysis techniques. Solubility testing of oligo-2-hdroxyphenylbenzaldimine was investigated by organic solvents such as DMF, THF, DMSO, methanol, ethanol, CHCl3, CCl4, toluene acetonitrile, ethyl acetate, conc. H2SO4, and aqueous alkaline solution. 2-Hydroxyphenylbenzaldimine (96%) was converted to oligomer by oxidation in an aqueous alkaline medium. According to solubility in water, oligo-2-hydroxyphenylbenzaldimine separated into two fractions: oligo-2-hydroxyphenylbenzaldimine (OHPBA-I, undissolved in water) and oligo-2-hydroxyphenylbenzaldimine (OHPBA-II, dissolved in water). According to the SEC technique, the number average molecular weight (M n), mass average molecular weight (M w), and polydispersity index (PDI) values of OHPBA-I and OHPBA-II were found to be 2166 g mol−1, 2591 g mol−1, and 1.196; 1736 g mol−1, 2509 g mol−1, and 1.445, respectively. Also, differential thermal analysis (DTA) and thermo gravemetric analyses (TGA) were shown to be stable of oligo-2-hydroxyphenylbenzaldimine against thermo-oxidative decomposition. The weight loss of OHPBA was found to be 93.63% at 1000°C.