Light-emitting devices photoluminescence

Metal complexes with Schiff base ligands have useful applications in organic optoelectronics due to their outstanding photoluminescent (PL) and electroluminescent (EL) properties, and their ease of synthesis, which readily allows structural modification for optimization of material properties.28 Hamada and co-workers pioneered the use of zinc(II) Schiff base complexes as blue to greenish white emitters for EL devices. We have demonstrated Pt(II) Schiff base triplet emitters as yellow dopants for organic light-emitting devices... 

Rhenium(I) tricarbonyl-2,2 -bipyridine moieties were used to cap both ends of a poly fluorine, yielding Re-capped Re(bpy)(CO)3(py)-X-(py)(CO)3(bpy)Re 2+ polymers, where X = polyfluorene [51, 52], The polymers with and without the Re caps were spin-coated from their solutions in CH2C12 onto an ITO surface previously modified with a layer of poly(styrene sulfonic acid), doped with poly(ethylenedioxythiophene). The LED (light-emitting device) was then topped with a layer of Ca/Al. The photoluminescence (PL) and electroluminescence seen were consistent with the presence of [Re(bpy)(CO)3(py)]+ [158],... 

Interest surged in studies of fluorescence after the discovery of electroluminescence from PPV (Burroughes et al., 1990), because of its potential for practical application in light emitting devices (LEDs). Electroluminescence is fluorescent emission produced by the recombination of electrons and holes injected into a thin film of conjugated polymer, and will be discussed in the next section. If photoluminescent emission from a polymer is weak, then the electroluminescence is unlikely to be of practical significance, and consequently studies of photoluminescence and photoluminescent quantum efficiency have been used as a means of selecting polymers likely to be useful in LEDs. 

Structures with CdS nanoelusters are promising candidates for of novel light-emitting devices. In the present work the photoluminescence (PL) of CdS nanoelusters in a Langmuir-Blodgett (LB) matrix of behenic acid and nanoelusters after removal of the matrix have been studied. 

Figure 12.3 Device characteristics for a polymer light-emitting device showing (a) the current-voltage characteristic (open circles) and the luminance-voltage characteristic (filled squares) and (h) the ahsorhance (Ahs) and photoluminescence (PL) spectra. The electroluminescence is very similar to the PL.

Polymer nanotubes composites are now extensively studied. Indeed, one may associate the properties of the polymer with those of nanotubes. This is the case of the mechanical reinforcement of standard polymer for example, but also one can take advantage of the specific electronic properties of the nanotubes. Therefore, we prepared composites with either saturated polymers like polymethylmethacrylate and MWNTs [27]. The electrical conductivity of these compounds as a function of the nanotube content exhibits for example a very low percolation threshold, (a few % in mass) and therefore they can be used as conducting and transparent layers in electronic devices such as Light Emitting Diodes (LEDs). Another type of composite that we have studied is based on the use of a conjugated polymer, polyphenylene-vinylene (PPV) known for its photoluminescence properties and SWNTs. We prepared this composite by mixing SWNTs to the precursor polymer of PPV. The conversion into PPV was subsequently performed by a thermal treatment at 300°C under dynamical vacuum [28],... 

Abstract. This article reviews mainly the results of our recent research on the relationship between the structure and the luminescence properties of PPV derivatives. PPV derivatives are particularly useful in an effort toward the establishment of such relationship because their chemical structures can be manipulated very systematically. Attachment of a wide variety of substituents, inclusion of kinky structural units, modification of main chain structures by inclusion of hole- and/or electron-transferring structures, and blending of polymers having different optical and electronic properties are representative approaches. The device characteristics of the light-emitting diodes (LEDs) fabricated from these polymers are discussed in relation to their structures. In certain cases, their photoluminescence (PL) properties are compared with their electroluminescence (EL) properties. 

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