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Herein are reported the syntheses of poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PF), poly(9,9-dioctylfluorene-alt-benzothiadiazole) (PFBT), and poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) by employing catalytic mechanochemical Suzuki polymerization in a ball mill. This mechanochemical synthesis technique can yield soluble functionalized polyfluorenes and its derivatives in 30 min or less. Furthermore, the polymer light emitting diode and photovoltaic interfacial electrolyte, poly(9,9-bis(3′-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluprene))dibromide (PFN-Br), was obtained via a facile mechanochemical quaternization reaction at the terminal amino groups of PFN. [ABSTRACT FROM AUTHOR]

Polymer Light Emitting Diodes (PLEDs), the most promising name in the field of display technology has received tremendous attention from various research groups. The research on light emitting polymers are an interdisciplinary zone which has challenging investigates on materials science and engineering, physics of device architecture and technology. This review addresses the wide range of tailored polymers, evolution of LED device structure for high performance, single and multicolor polymer based LEDs. Though, polymers are possessing better efficiency and easy fabrication processes, it has very low stability and short life. This study also reviews, device degradation during device fabrication and operation. [ABSTRACT FROM AUTHOR]

This paper has investigated the synthesis of plasma-polymerized pyrrole (pPPy) nano-particles grown by the proposed atmospheric pressure plasma jets (APPJs) through the parametric studies, especially input power and gas flow rate. The transition of conventional streamer-like into intense and glow-like discharges necessary for fully cracking the monomer was observed to be strongly dependent on both input power and gas flow rate. The intense and glow-like discharge was produced only when adopting the specific parametric condition,i.e., a gas flow rate of 1600 sccm and input power with 12.5 kV, thereby resulting in obtaining the synthesized pPPy nano-particle structures with highly cross-linked networks and many double bonds. The plasma-flow characteristics were investigated based on the non-plasma flow numerical simulation, and also analyzed by the voltage, current, infrared, and optical emission spectroscopy (OES). The synthesized pPPy films were analyzed by field-emission scanning electron microscopy (FE-SEM) and Fourier infrared spectroscopy (FT-IR). It is anticipated that the high-quality plasma polymer grown by the proposed APPJs contributes to serving as conducting electrode-materials of a flexible polymer light emitting diode (P-LED). [ABSTRACT FROM AUTHOR]

In typical fluorescent organic light emitting diodes (LEDs), the observation of triplet excitons is difficult because of their non-radiative features of decay. The generation process of triplet excitons was successfully monitored by employing spectroscopic techniques combined with LED operation. The generation dynamics of singlet excitons are then simultaneously examined by time-resolved electroluminescence measurements, enabling relative comparison of the generation processes of singlet and triplet excitons. As a result, the generation ratio of singlet excitons is shown to be enhanced by applied voltage. The enhancement is concluded to result from the increase of the generation rate in signlet excitons induced by electric field. [ABSTRACT FROM AUTHOR]

Floating-off film-transfer technique was used for the formation of semiconducting polymer multi-layers and the effect on the performance of polymer light-emitting diode (PLED) was studied. This method made it possible to avoid the solvent compatibility problem that was typically encountered in successive coating of polymeric multilayer by solution processing. F8BT and MEH-PPV were used for electron transporting layer (ETL) and for emissive layer, respectively. Current-voltage-luminance characteristics and luminescence efficiency results showed that the insertion of ETL by floating-off film-transfer technique followed by proper heat treatment resulted in a significant improvement in PLED operation due to its electron-transporting and hole-blocking abilities. [ABSTRACT FROM PUBLISHER]

We report on fabrication and characterization of polymer light emitting diode by using a thin film of pure deoxyribonucleic acid as electron blocking layer (EBL). A thin film of phosphorescent Ir(ppy)3luminophore, embedded in the poly(N-vinylcarbazole) (PVK)/2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) is used as emission layer. The obtained BioLED shows a good stability and its luminous efficiency is improved byca40% as compared to the case without EBL. The result shows that using the DNA layer one can either improve the OLED brightness at the same current density or operate at a significantly lower current density with the same brightness than without it. [ABSTRACT FROM PUBLISHER]

In a homemade UV-Ozone generator, different ignition tubes extracted from HID mercury vapor lamps were investigated, namely: 80, 125, 250 and 400 watts. The performance of the generator in function of the type of the ignition lamp was monitored by the measurements of the ozone concentration and the temperature increment. The results have shown that the 400 W set up presented the highest ozone production, which was used in the treatment of indium tin oxide (ITO) films. Polymer light emitting diodes were assembled using ITO films, treated for 10, 20 and 30 min, as an anode. The overall results indicate improvement of the threshold voltage (reduction) and electroluminescence of these devices. [ABSTRACT FROM AUTHOR]

Admittance Spectroscopic analysis was applied to study the effect of LiF buffer layer and to model the equivalent circuit for poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV)-based polymer light emitting diodes (PLEDs) with the LiF cathode buffer layer. The single layer device with ITO/MEH-PPV/Al structure can be modeled as a simple combination of two resistors and a capacitor. Insertion of a LiF layer at the Al/MEH-PPV interface shifts the lowest unoccupied molecular orbital (LUMO) level and the vacuum level of the MEH-PPV layer as a result of which the barrier height for electron injection at the Al/MEH-PPV interface is reduced. The admittance spectroscopic analysis of the devices with the LiF cathode buffer layer shows reduction in contact resistance (RC), parallel resistance (RP) and increment in parallel capacitance (CP). [ABSTRACT FROM AUTHOR]