No abstract

No abstract

No abstract

The composition of the surface and electrical properties of silicon oxide nanocomposites of porous silicon were investigated by FTIR spectroscopy in the range of 400 – 4000 cm-1and by impedance spectroscopy in the frequency range of 25 Hz – 1 MHz. It was revealed the different dispersion of electrical capacitance in different frequency bands and the complex relaxation processes that affect the electrical transport properties of nanocomposites. The correlations between the IR absorption spectra of silicon oxide composites and processes of charge transfer was defined. On the basis of analysis of spectra of thermal stimulated depolarization it was shown that oxidation of the surface of porous silicon nanocrystals gives rise to changing the density of states in different energy ranges.

No abstract

Abstract-We report the influence of the thickness of a copper iodide (CuI) hole injection layer (HIL) on the performance of organic light-emitting diodes (OLEDs) with tris-8-hydroxyquinoline aluminum (Alq3) active layer and aluminum cathode layer. The investigation of structural and morphological properties of thermally evaporated CuI thin films indicates that they are amorphous. OLEDs with the ITO/CuI/Alq3/poly(ethylene glycol) dimethyl ether/Al structures were fabricated and current density-voltage, luminance-voltage and current efficiency-current density were analyzed. The maximal luminescence current efficiency is obtained for the devices with a CuI thickness of 12nm.Display technologies that utilize organic light-emitting diodes (OLEDs) were commercialized at the end of the last century and have been continually developed until the present time [1][2][3]. One active direction of current research is the synthesis and characterization of new holeinjection and electron-injection materials. Hole injection layers (HIL) and electron injection layers (EIL) enhance the luminescence current efficiency of OLEDs [4][5][6]. For example, polyaniline [7], poly(3,4-ethylenedioxythiophene) (PEDOT) [8][9], metal phthalocyanines [10] and metals with high work functions [11][12] are successfully used as HILs. These materials decrease the hole injection barrier between the anode and the organic active layer.Recently we have reported that CuI thin films can be used as effective HILs in the pentacene-based photovoltaic structures [13], as an efficient injection layer of holes from the ITO anode in a light-emitting diode structure based on Alq 3 [14], and solid-state dyesensitized solar cells [15].CuI thin films deposited by thermal evaporation are on average 80% transparent over the 400-800nm wavelength range [13]. CuI material has low cost and therefore is promising for practical applications in organic optoelectronic devices.The aim of this work is to characterize the structural and morphological properties of CuI thin films and to investigate the influence of the thickness of the CuI hole * E-mail: stakhira@polynet.lviv.ua injection layer on the performance of organic lightemitting devices.CuI, Alq 3 , poly(ethylene glycol) dimethyl ether (PEGDE) and Al layers for OLEDs were deposited using thermal evaporation of the corresponding powders from molybdenum boats in a vacuum chamber with the base pressure lower than 10 -3 Pa [14]. The layers were grown on ITO-coated glass substrates (Sigma Aldrich, 100Ω/sq) ultrasonically pre-cleaned using acetone and water. The substrates were held at room temperature during the deposition. The deposition rates of Alq 3 , PEGDE [16] and Al were 0.3nm/s, 0.4nm/s and 6nm/s, and the resulting thicknesses were 40nm, 3nm and 150nm, respectively. CuI powders were heated to 300°C which resulted in a deposition rate of 0.3nm/s. The thickness of CuI layers in five reported OLEDs was 0nm, 5nm, 8nm, 12nm, 18nm, and 30nm, as determined from the ellipsometry measurements. The active area of the ITO/CuI/Alq ...

No abstract

No abstract