Photoluminescence polymer-emitting layer

The various functional layers in PLED devices are outlined in Figure 10.14. By applying a voltage across the device, electrons and holes are injected into the photoluminescent polymer, where they recombine to form excitons and emit light. Suitable, commonly used emissive polymers are conjugated materials such as poly(phenylenevinylene)s (PPVs) and polyfluorenes. 

DPAs and 1-phenyl-1-alkynes show intense photo- and electroluminescences. A systematic investigation on the luminescence of poly(DPAs) has revealed that these polymers exhibit photoluminescence around 530 nm and electroluminescence around 550 nm. In a similar way, poly(l-phenyl-1-alkynes) photochemically and electrochemi-cally emit strong lights with spectral maxima located around 455 and 470 nm, respectively. Green and blue emissions are observed from the electroluminescent devices using poly(DPAs) and poly(l-phenyl-1-alkynes) as the emission layers, respectively. ... 

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],... 

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],... 

Copolymers containing alternating l,4-bis(phenylethenyl)benzene, l,4-bis(phenylethenyl)-2,5-dimethoxybenzene or l,5-bis(phenylethenyl)naphthalene chromophores, and dibenzo-24-crown-8 spacers within the polymer backbone, best represented by 87, showed blue light emission in solution, and tunable photoluminescence and electroluminescence depending on the structure of the chromophore. Blends of these copolymers with a small amount of poly(ethylene oxide), and lithium salt as active layers, form efficient light-emitting electrochemical cells <2003JMC800>. 

Crystalline silicon is the most widely used semiconductor material today, with a maiket share of above 90%. Because of its indirect electronic band structure, however, the material is not able to emit light effectively and therefore carmot be used for key applications like light-emitting diodes or lasers. Selected one- or two-dimensional silicon compounds like linear or branched polysilylenes [1] or layered structures like siloxene [2], however, possess a direct band gap and therefore exhibit intense visible photoluminescence. Siloxene, a solid-state polymer with a sheet-like layered structure and an empirical formula Si H (OH) , in particular, is considered as an alternative material for Si-based liuninescent devices. Detailed studies of stmctural and photophysical properties of the material, however, are strraigly impeded by its insolubility in organic solvents. 

The oscillatory dependence on the thickness (d) of the polymer layer arises from the proximity of the metallic mirror electrode (the cathode) the emitting oscillator interacts with the virtual image oscillator behind the mirror [36, 37]. Because the radiation from the emitter and the retarded radiation from the image oscillator interfere, the PL decay rate is an oscillatory function of the distance from the mirror. Consequently, for a thin film, the quantum yields for photoluminescence and electroluminescence are oscillatory functions of d. 

Poly(p-phenylenevinylene) derivatives are promising candidates for the active layer of polymer light-emitting diodes. Thus, various types of substituted poly(p-phenylenevinylene)s have been synthesized. Whereas these derivatives are soluble in organic solvents, a high-quality thin film of these polymers can be formed. Die optical properties of these polymers have been reviewed previously [8, 169]. The electroluminescence spectrum of the device fabricated with a conjugated pofymer is almost the same as that of the photoluminescence spectrum of the thin film of the polymer. The peaks in photoluminescence spectra are compiled in Table XVII [170, 171]. 

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