Results 1 - 10 of 2748
Results 1 - 10 of 2748. Search took: 0.028 seconds
|Sort by: date | relevance|
[en] Present article is devoted to identification of elastic stresses in heterostructures Ga In As P/In P with ultrafine active region on the polarization of radiation. Two methods of record of polarization-dimensional effect were proposed.
[en] Methods for the synthesis of styrylazines and styrylbenzazines are considered, their photophysical and photochemical properties are analyzed. The review covers both published data and own works of the authors. Important data on the prospects of application of arylhetarylethenes as components of electroluminescence materials are discussed. The bibliography includes 124 references.
[en] We fabricated hybrid structures using combined properties of organic and inorganic materials for application in light emitting diode. The hybrid structures were demonstrated using poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as organic materials and n-GaN as inorganic materials. To investigate the effects of organic layer thickness, we changed polymer concentration and spin speed of MDMO-PPV solution. We obtained current rectifying behaviour with MDMO-PPV layer of approximate 60 nm thickness. The hybrid structure shows broad emissions covering orange range in both photoluminescence and electroluminescence spectra and its band structures matched well with energy band gap of GaN and MDOM-PPV. We expect the potential applications and the enhanced efficiency in optoelectronic devices with hybrid structure by making progress the results. -- Highlights: • We fabricated the hybrid structures using MDMO-PPV, PEDOT:PSS and n-GaN. • We investigated the effects of organic layer thickness in hybrid devices. • These results will provide a guide to develop the hybrid optoelectronic devices
[en] The photo- and electroluminescence spectra of silicon-based structures formed by direct bonding with simultaneous doping with rare-earth metals are studied. It is shown that emission in the visible and IR spectral ranges can be obtained from n-Si:Er/p-Si and n-Si:Eu/p-Si structures fabricated by the method suggested in the study. The results obtained make this method promising for the fabrication of optoelectronic devices
[en] This thesis reports on the synthesis and characterisation of various poly(phenylenevinylene) (PPV) polymers with various structure and using various polymerisation methods to investigate the stereoregularity of the materials and with an aim to produce polarised electroluminescence. The Wittig reaction has been used to prepare both main-chain and flexible spacer PPV materials. A series of model compounds based upon distyrylbenzene was also synthesised as an aid to fully characterising the above polymers. These materials were incorporated into LED devices to test their emissive properties. With an aim to produce more stereoregular materials, the Wadsworth-Emmons reaction was employed to re-synthesise the main-chain and the flexible spacer polymers. The resultant polymers were of much higher stereoregularity and molecular weight. The electroluminescent characteristics showed a slight improvement over those from the Wittig materials. The Heck reaction was also used to synthesise the main-chain PPV materials to compare the stereoregularity of the resultant materials. The above materials were investigated using X-ray diffraction to understand the liquid crystalline behaviour of the polymer melts. Reactive mesogens were also synthesised as an alternate route to producing aligned fluorescent films that could be incorporated into a LED. Compounds that showed liquid-Crystallinity over a wide temperature were developed and then photo-polymerised into an intractable network. (author)
[en] We demonstrate an improved efficiency in OLEDs with a thin Alq3 interlayer, which is inserted into the hole-transport layer for adjusting the hole-injection and transport, and improving the hole-electron balance. The thin Alq3 interlayer can effectively influence the electrical performance and electroluminescence (EL) efficiency of the devices. The devices with an optimum Alq3 interlayer exhibit a maximum EL efficiency of around 3.3 cd/A, which is improved by a factor of two over the conventional devices (1.6 cd/A) without the interlayer
[en] Current-voltage characteristics of surface-irradiated photodiodes based on the InAsSbP/InAs structures are analyzed using experimental data on the distribution of electroluminescence intensity over the diode surface and taking into account thickening the current streamlines near the contacts. The influence of the potential barrier associated with the N-InAsSbP/n-InAs junction in double heterostructures on the differential resistance of diodes under zero bias, the value of the reverse current, and spreading of the forward current is discussed.
[en] The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface (ΔEc = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence (EL) spectrum. In the entire temperature range under study, T = 290–480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated as a result of the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the EL intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290–345 K, and a linear increase is observed at T > 345 K. This work for the first time reports an increase in the emission power of a light-emitting diode structure with increasing temperature. It is shown that this rise is caused by a decrease in the threshold energy of the impact ionization due to narrowing of the band gap of the active region
[en] Improved efficiency and colour purity of blue electrophosphorescent devices based on bis[(4,6-difluorophenyl)-pyridinato-N,C2](picolinato)Ir(III) (FIrpic) were demonstrated by codoping a fluorescent emitter 2,5,8,11-tetra-t-butyl-perylene (TBPe). The optimized device codoped with 8 wt% FIrpic and 0.15 wt% TBPe shows a maximum current efficiency and power efficiency of 11.6 cd A-1 and 7.3 lm W-1, which were increased by 20% and 40%, respectively, compared with that of the reference device. Also, a blue shifted electroluminescent spectrum of the codoped devices was observed with doping concentration of TBPe, leading to improved colour purity of the devices. The improved efficiency and colour purity of the codoped devices were attributed to the simultaneous emission of the two emitters