Electroluminescence spectra

The electroluminescence spectra of the single-layer devices are depicted in Figure 16-40. For all these OPV5s, EL spectra coincided with the solid-state photoluminescence spectra, indicating that the same excited states are involved in both PL and EL. The broad luminescence spectrum for Ooct-OPV5-CN" is attributed to excimer emission (Section 16.3.1.4). 

FIGURE 4.7 (Left) Chemical structures of PPLED materials. (Right) The device structure and the electroluminescence spectra of the PPLEDs prepared with PYK (4) host polymer and the above dopants (5wt%). (From Kawamura, Y., Yanagida, S., and Forrest, S.R., J. Appl. Phys., 92, 87, 2002. With permission.)... 

Figure 9. Electroluminescence spectra from an n-GaP electrode under about —2.5 V (SCE) in a 0.3M ferro- and ferricyanide solution at pH 13...

Rutz [13] reported a broad near-UV band in the electroluminescence spectra, extending from 215 nm into the blue aid of the visible range. Moiita et al [14] observed the cathodoluminescence with peaks or humps in epitaxial AIN films on (0001) sapphire substrates at about 2.71, 2.88, 3.12, 3.19, 3.33 and 3.53 eV. They insisted that the last two peaks were due to nitrogen vacancies or interstitial Al impurities, and that the first two peaks were attributed to oxygen impurities or defects induced by the increase in oxygen concentration. 

Figure 11.30 The electroluminescence spectra obtained from RE tris(8-hydroxyquinoline) (REQ, RE = Nd, Er, or Yb) based OLEDs [82]. (Reproduced from Current Opinion in Solid State Materials Science, 5, no. 6, R.J. Curry and W.R GiUin, Electroluminescence of organolanthanide based organic tight emitting diodes, 481-486, 2001, with permission from Elsevier.)...

Iridium(in) /8-diketonates show a relatively week absorption in the 350-400 nm range, that can be ascribed to spin-aUowed MLCT transitions. Electroluminescent spectra (EL) show green light emission. In electronic spectra of Ir(III)), Pt(II), Ru(II) and Os(II) /3-diketonates " weak absorption bands between 330 and 560 nm can be assigned to singlet and triplet MLCT transitions. The n n transition from the complexes are blue-shifted for about 20 mn compared with the free ligands. 

Figure 8 (right) Polarised electroluminescence spectra from an ITOtruhhed PPVtPFOl Ca LED. The upper curve is for light emitted with polarisation parallel to the orientation direction and the lower curve for perpendicular polarisation. The anisotropy, IparaUei I perpendicular, hos a peak valuc of 25 1. 

In order to remove the reaction by-products and other impurities the as-prepared nanociystals were precipitated by the addition of non-solvent (typically, 2-Propanol) and redissolved in pure water. Indium tin oxide (ITO) coated glass slides (13 Ohm/cm thickness of ITO layer of 125 nm, unpolished, Merck) were used as substrates for LbL assembly and as transparent positive electrodes. Aluminium layers evaporated with a lab coating machine B30.3-T (Malz Schimdt) play a role of cathode. PL measurements were performed at room temperature using a FluoroMax-2 spectrofluorimeter (Instruments SA). Electroluminescence spectra were measured with the same device by positioning the NEED in the focus of the detecting channel. 

New results on the influence of uniaxial stress up to / = 4 kbar along [110] and [1-10] directions on the electroluminescence spectra of laser diode nanostructures p-ALGai-xAs/GaAsi.yP,/ -AlxGai.xAs are presented. With the increasing stress, the emission spectra demonstrate a blue shift of up to 20-25 meV at P = 3-4 kbar, while the electroluminescence intensity and light efficiency increase under compression. The results are discussed in terms of changes in the band structure under an uniaxial compression. 

H. Noguchi, T. Kondo, K. Murakoshi, and K. Uosaki, Visible electroluminescence from n-type porous silicon/electrolyte solution interfaces Time—dependent electroluminescence spectra, J. Electrochem. Soc. 146(11), 4166, 1999. 

FIGURE 4.5. Electroluminescence spectra from three devices which have different optical thicknesses. The presence of a second mode in one of the spectra is a result of a closer than ideal mode spacing, If the refractive index difference between the materials that constitute the QWS is enhanced, the total optical thickness will be reduced and the mode spacing increased. 

FIGURE 4.9. Electroluminescence spectra (along the cavity axis) from three representative cavity devices from the same substrate but with a terraced filler (as in Fig. 4.2). The anode is a 55-nm-thick ITO layer. The three spectra have major peaks at (a) 625 run, (b) 512 nm, and (c) 545 nm. The measured external quantum efficiencies (in units of photons/electron) are also indicated in each case. 

FIGURE 4.10. Electroluminescence spectra (along the normal to the plane of the substrate) from a cavity LED and a reference noncavity LED excited by the same injection current. The active materials for both devices were deposited simultaneously. 

FIGURE 4.12. Electroluminescence spectra from a noncavity LED with an emissive layer consisting of Alq doped with 0.5% pyrromethene. Also shown is the EL spectrum of a LED with an Alq emissive layer. The spectra have been scaled so that the areas are proportional to the measured external quantum efficiencies. 

FIGURE 4.13. Normalized electroluminescence spectra of Alq/NAPOXA/TAD LEDs as a function of NAPOXA thickness x (in X). In the inset is shown the fraction of the total LED light output originating in the Alq as a function of x together with a fit to the data points. 

FIGURE 4.15. Electroluminescence spectra from two noncavity devices with the structure shown in Fig. 4.14b. The thicknesses of the undoped Alq layers in the two devices are 20 nm and 30 nm. 

FIGURE 10.18. Electroluminescent spectra of a BDOH-PF LEC initial EL and the EL after long-term stress. The initial EL is blue and the long-term stress EL changes to bluegreen. The PL spectrum of a thin film of BDOH-PF is also shown for comparison. (From Ref. 33.)... 

FIGURE 10.22. Polarized electroluminescence spectra from an aligned ITO/PPV/PFO/Ca LED. The spectra were measured for light polarized parallel (open triangles) and perpendicular (open circles) to the rubbing direction. (From Ref. 35.)... 

FIGURE 10.39. The electroluminescence spectra of PtOEP/PFO LEDs. The spectra are normalized to the phosphorescence peak at 646 nm and offset for comparison. (From Ref. 72.)... 

Figure 1.7. GaN blue LEDs by MOC VD (a) Electroluminescence spectra and (b) Structure of a buffer layer [22]...

Figures 4 and 5 show typical I-V curves and electroluminescence spectra collected by ARL for 280nm UV LEDs. Analysis of the 1-V curve for the 280nm UV LED gives a series resistance of only 9D, indicating excellent electrical properties of the n- and p-type layers of this structure. An optical power output of 0.6 mW was obtained at 20mA and an operating voltage of 5.39V. This gives a wall-plug efficiency of 0.56% for this...

Finally, the anthracene-based [2] rotaxanes were studied in single layer OLED architecture [73, 74], The measurements revealed new features in electroluminescence spectra comparing to photoluminescence both in solid state and in solution. However, the origin of the phenomena is not still well understood and far to be exploited in applications. 

Figure 16-40. Normalized electroluminescence spectra of the ITO/OPV5/A1 devices U-OPV5...

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