M. A. Mohd Sarjidan

Study and fabrication of europium picrate triethylene glycol complex

A mononuclear of [Eu(NO3)(Pic)(H2O)2(EO3)](Pic)·(0.73)H2O complex, where EO3=trietraethylene glycol and Pic=picrate anion, shows a red emission when used as an active layer in a single layer of ITO/EO3-Eu-Pic/Al configuration. The crystal structure of the complex consists of [Eu(NO3)(Pic)(H2O)2(EO3)]+ cation and [Pic]- anion. The Eu(III) ion is coordinated to the 10 oxygen atoms from one EO3 ligand, one Pic anion, one nitrate anion, and two water molecules. The complex is crystallized in triclinic with space group P-1. The hybrids in thin films I and II were prepared in the respective order solution concentrations of 15 and 20 mg/mL the emissive center. Comparing the photoluminescence (PL) and electroluminescence (EL) spectra, we can find that all emissions come from the characteristic transitions of the Eu(III) ion. The EL spectra of both thin films showed the occurrence of the most intense red-light emission around at 612 nm. Comparison of organic light-emitting device (OLED) current intensity characteristics as a function of voltage (I-V) show that the thin film I is better than those found for the thin film II. The thickness of the emitting layer is an important factor to control the current-voltage curve. The sharp and intense emission of the complex at low voltage indicates that the complex is a suitable and promising candidate for red-emitting materials.

Electroluminescence and negative differential resistance studies of TPD:PBD:Alq3 blend organic-light-emitting diodes

Ternary system of single-layer organic-light-emitting diodes (OLEDs) were fabricated containing tris(8-hydroxyquinoline) aluminium (Alq 3) blended with N,N ′-diphenyl-N,N ′-bis(3-methylphenyl)-1,1 ′-biphenyl-4,4 ′-diamine and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole small molecules. Electroluminescence properties were investigated with respect to blend systems. Significant improvement in turn-on voltage and luminance intensity was observed by employing the blends technique. Negative differential resistance (NDR) characteristics observed at a low voltage region in blended OLED is related to the generation of guest hopping site and phonon scattering phenomenon. However, luminescence of the devices is not altered by the NDR effect.

Junction properties and conduction mechanism of new terbium complexes with triethylene glycol ligand for potential application in organic electronic device

Terbium-picrate triethylene glycol (EO3-Tb-Pic) complex was prepared in thin film and single layer device structure of ITO/EO3-Tb-Pic/Al, using spin coating technique. The UV-Vis absorption spectroscopy analysis was performed to evaluate the elec- tronic molecular transition of the complex. The optical band gap, Eg estimated from the Tauc model revealed that EO3-Tb-Pic thin film exhibited a direct transition with Eg of 2.70 eV. The electronic parameters of the ITO/EO3-Tb-Pic/Al device such as the ideality factor n, barrier height Φb, saturation current Io, and series resistance Rs, were extracted from the conventional lnI-V, Cheungs func- tions and Nordes method. It was found that the evaluated parameters calculated from Nordes and Cheungs methods were consistent with those calculated from the conventional I-V method. In the double logarithmic I-V plot, three distinct regions based on the slope were identified, and the conduction mechanisms were discussed and explained. The mobility, μ value was estimated from SCLC re- gion as 2.58×10 -7 cm 2 /(V·s). This newly obtained lanthanide complex may be potentially utilized in electronic devices.

Structural and Optical Properties of Nickel-Doped and Undoped Zinc Oxide Thin Films Deposited by Sol-Gel Method

ZnO thin films with and without Ni-doping were successfully deposited by sol-gel method with zinc acetate dihydrate as inorganic precursor, and nickel (II) acetate tetrahydrate as dopant. The solutions were prepared by dissolving zinc acetate and nickel (II) acetate in ethanol and diethanolamine (DEA) as its chelating agent. Thin films were fabricated by using spin-coating method on glass substrates. ZnO films were obtained by pre-heating and post-heating at 300 °C for 10 minutes and 500 °C for 1 h respectively. The films were analyzed by X-ray diffraction (XRD), UV-Vis transmittance and photoluminescence (PL). All samples exhibit high transparency in visible. Ni dopant does not alter so much ZnO structure, which due to the ion substitution between Ni and Zn. However, the Ni tends to create a dopant energy interlayer in ZnO energy band gap which cause significant change in PL intensity.

Annealing Effect on Small Molecules Blend Organic Light-Emitting Diodes

This research work investigates the influence of the annealing process upon the performance of photo-emissive layer of organic light-emitting diode (OLED). The photo-emissive layer consists of a ternary blend of N, N-diphenyl-N,N-bis (3-methylphenyl)-(1,1-biphenyl)-4,4-diamine (TPD), 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) and tris-8-hydroxyquinoline (Alq3), to produce TPD:PBD:Alq3 (at 1:1:1 ratio) blend thin films, in which the material solutions are deposited onto clean substrate via spin-coating method. The samples were annealed at 100°C in 10, 20 and 30 minute of time in an open-air condition. The results reveal that the annealing process at 10 minutes produces an optimum performance of the ternary OLED.

Fabrication and Characterization of Organic Light-Emitting Diodes Containing Small Molecules Blends as Emissive Layer

Organic light-emitting diodes (OLEDs) were fabricated containing guest molecule of Tris (8-hydroxyquinoline) aluminum (Alq3) blend with host molecules of N,N-diphenyl-N,N-bis (3-methylphenyl)-1,1-biphenyl-4,4-diamine (TPD) and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) small molecules. Optical, photoluminescence (PL) and electroluminescence (EL) properties were investigated with respect to blend systems. The obtained optical energy gap and PL intensity in the blend systems increased due to the transfer of high energy from the host to guest molecules. Luminance and current efficiency were enhanced for blended OLEDs as compared to that of pure Alq3, related to high exiton recombination in guest caused by high injection and accumulation of charge carrier.

Optical, Structural and Electrical Study of Organic Light Emitting Diode (OLED)Based on MEH/PPV:C60 Composite

The influence of C60 on absorption, photoluminescence (PL) and luminescence properties of a single layer MEH/PPV:C60 organic light emitting diode has been investigated. The MEH/PPV molecules were mixed with 5 wt%, 20 wt% and 50 wt% of C60 and stirred in toluene. The emissive layer of OLED was deposited the MEH/PPV:C60 mixture solution on cleaned ITO by spin‐coating at 3000 rpm in 40 s. The absorption and PL characterization of the spin‐cast films were carried out using UV/Vis/NIR spectrometer (Jasco V‐570) and luminescence spectrometer (Perkin Elmer, LS50B), respectively. The current‐voltage (I–V) properties of OLED were obtained using source measurement unit (SMU) (2400, Keithley Instrument).

Fabrication and Characterization of New Hybrid Organic Light Emitting Diode (OLED): Europium‐picrate‐triethylene oxide Complex

Thin‐film light emitting devices based on organic materials have attracted vast interest in applications such as light emitting diode (LED) and flat‐panel display. The organic material can be attached with inorganic material to enhance the performance of the light emitting device. A hybrid OLED based on a new complex of europium picrate (Eu‐pic) with triethylene oxide (EO3) ligand is fabricated. The OLED is fabricated by using spin coating technique with acetone as the solvent and aluminum as the top electrode. The optical, photoluminescence (PL) and electrical properties of the sample are carried out by UV‐Vis spectroscopy (Jasco V‐750), luminescence spectroscopy (Perkin Elmer LS‐500) and source measure unit (SMU) (Keithly), respectively.