Photoluminescence electroluminescence

Keywords Poly(para-phenylene)s, Poly(para-phenylenevinylene)s, Oligomers, Photoluminescence, Electroluminescence, Light emitting diodes. 

L.S. Swanson, J. Shinar, Y.W. Ding, and T.J. Barton, Photoluminescence, electroluminescence, and optically detected magnetic resonance study of 2,5-dialkoxy derivatives of poly(p-phenylene acetylene) (PPA) and PPA-based light-emitting diodes, Synth. Met., 55 1-6, 1993. 

Luminescence covers all emissions of light in the near IR, VIS and near UV spectral regions. The origin of the luminescence can be specified as photoluminescence , electroluminescence , chemiluminescence , or bioluminescence for example. These definitions depend on the mode of formation of the excited molecule which eventually emits the luminescence. 

The incorporation of siloles in polymers is of interest and importance in chemistry and functionalities. Some optoelectronic properties, impossible to obtain in silole small molecules, may be realized with silole-containing polymers (SCPs). The first synthesis of SCPs was reported in 1992.21 Since then, different types of SCPs, such as main chain type 7r-conjugated SCPs catenated through the aromatic carbon of a silole, main chain type cr-conjugated SCPs catenated through the silicon atom of a silole, SCPs with silole pendants, and hyperbranched or dendritic SCPs (Fig. 2), have been synthesized.10 In this chapter, the functionalities of SCPs, such as band gap, photoluminescence, electroluminescence, bulk-heterojunction solar cells, field effect transistors, aggregation-induced emission, chemosensors, conductivity, and optical limiting, are summarized. 

Keywords Silicon, germanium, carbon, alloys, nanostructures, optoelectronics, light emission, photoluminescence, electroluminescence, quantum well, quantum wire, quantum dot, superlattices, quantum confinement. 

The octahedral Ru complex [Ru(bipy)3] (bipy=2,2 -bipyridyl) exhibits efficient photoluminescence, electroluminescence, and also electrochemically-generated chemiluminescence (quantum yields up to 5-7%) through the reactions shown in Eqs. 2.18a and 2.18b, respectively (excited states are labelled ) [68-70]. These properties have led to a range of studies on polymers with appended polypyridyl and related complexes. 

According to P, Alivisatos et al, [31], the advantages of nanocomposite LEDs originate from the fact that the band gap can be tailored and hence, due to quantum confinement, the emission color changes depending on the size of the nanoparticles (see Sect, 2), This phenomenon is well illustrated in Fig, 9, which displays the effects of quantum confinement in photoluminescence, electroluminescence and optical absorption spectra. 

Figure 14 Disubstituted acetylene polymers that show photoluminescence, electroluminescence, and related functions.

Figure 9-12. Absorption (Abs), photoluminescence excitation spectrum (PLCX), pholo-lumincscence (PL), and electroluminescence (EL) emission of mLPPP.

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). 

Fig. 1. Absorption and photoluminescence dashed line) spectra of a thin film of LPPP 26 and electroluminescence solid line) spectrum of an ITO / LPPP 26 (60 nm) / A1 device (from [50])...

Numerous ternary systems are known for II-VI structures incorporating elements from other groups of the Periodic Table. One example is the Zn-Fe-S system Zn(II) and Fe(II) may substimte each other in chalcogenide structures as both are divalent and have similar radii. The cubic polymorphs of ZnS and FeS have almost identical lattice constant a = 5.3 A) and form solid solutions in the entire range of composition. The optical band gap of these alloys varies (rather anomalously) within the limits of the ZnS (3.6 eV) and FeS (0.95 eV) values. The properties of Zn Fei-xS are well suited for thin film heterojunction-based solar cells as well as for photoluminescent and electroluminescent devices. 

It was observed in other works that in sulfide electrolyte, decomposition of ZnSe was still obtained stable PECs could be constructed though from singlecrystal, n-type, Al-doped ZnSe electrodes and aqueous diselenide or ditelluride electrolytes [124]. Long-term experiments in these electrolytes were accompanied by little electrode weight loss, while relatively constant photocurrents and lack of surface damage were obtained, as well as competitive electrolyte oxidation. Photoluminescence and electroluminescence from the n-ZnSe Al electrodes were investigated. 

Zinc sulfide, with its wide band gap of 3.66 eV, has been considered as an excellent electroluminescent (EL) material. The electroluminescence of ZnS has been used as a probe for unraveling the energetics at the ZnS/electrolyte interface and for possible application to display devices. Fan and Bard [127] examined the effect of temperature on EL of Al-doped self-activated ZnS single crystals in a persulfate-butyronitrile solution, as well as the time-resolved photoluminescence (PL) of the compound. Further [128], they investigated the PL and EL from single-crystal Mn-doped ZnS (ZnS Mn) centered at 580 nm. The PL was quenched by surface modification with U-treated poly(vinylferrocene). The effect of pH and temperature on the EL of ZnS Mn in aqueous and butyronitrile solutions upon reduction of per-oxydisulfate ion was also studied. EL of polycrystalline chemical vapor deposited (CVD) ZnS doped with Al, Cu-Al, and Mn was also observed with peaks at 430, 475, and 565 nm, respectively. High EL efficiency, comparable to that of singlecrystal ZnS, was found for the doped CVD polycrystalline ZnS. In all cases, the EL efficiency was about 0.2-0.3%. 

Strickert HH, Tong JR, EUis AB (1982) Luminescent photoelectrochemical cells. 6. Spatial aspects of the photoluminescence and electroluminescence of cadmium selenide electrodes. J Am Chem Soc 104 581-588... 

Ouyang J, Pan ERE, Bard AJ (1989) Semiconductor Electrodes, 62. Photoluminescence and electroluminescence from manganese-doped ZnS and CVD ZnS electrodes. J Electrochem Soc136 1033-1039... 

Many of the linear conjugated tricyclic systems have interesting fluorescence or other electrophysical properties. Bis-pyrazolepyridines such as compound 30 have been incorporated into polymers as fluorescent chromophores <1999JMC339>, and used in doped polymer matrices <1997JMC2323>. They are electroluminescent at 425 nm and photoluminescent at 427 and 430 nm in a poly(vinylcarbazole) matrix with a quantum efficiency of 0.8. 

It is worth summarizing at this point the different excitation methods used for phosphors that will be referred to throughout this chapter. There are three types photoluminescence (PL) which is based on initial excitation by absorption of light, cathodoluminescence (CL) which is based on bombardment with a beam of electrons, as in a cathode ray tube (CRT) and electroluminescence (EL) which is based on application of an electric field (either a.c. or d.c.) across the phosphor. 

The term chemiluminescence was not introduced until 1888, when Wiedemann defined the term luminescence. He was able to classify luminescence phenomena of six different kinds, according to the manner of excitation photoluminescence, caused by the absorption of light, electroluminescence, produced in... 

Figure 11.9. NW LED. (a) Crossed InP nanowire LED. (top) Three-dimensional (3D) plot of light intensity of the electroluminescence from a crossed NW LED. Light is only observed around the crossing region, (bottom) 3D atomic force microscope image of a crossed NW LED. (inset) Photoluminescence image of a crossed NW junction, (b-c) Multicolor nanoLED array, (b) Schematic of a tricolor nanoLED array assembled by crossing one n-GaN, n-CdS, and n-CdS NW with a p-Si NW. The array was obtained by fluidic assembly and photolithography with ca. 5- xm separation between NW emitters, (c) Normalized EL spectra obtained from the three elements. [Reprinted with permission from Ref. 59. Copyright 2005 Wiley-VCH Verlag.]...

FIGURE 1.10 Optical absorption, photoluminescence and electroluminescence (circle) of Covion SY film. 

MR Andersson, G Yu, and AJ Heeger, Photoluminescence and electroluminescence of films from soluble PPY-polymers, Synth. Met., 85 1275-1276, 1997. 

D.M. Johansson, M. Theander, G. Srdanov, G. Yu, O. Inganas, and M.R. Andersson, Influence of polymerization temperature on molecular weight, photoluminescence, and electroluminescence for a phenyl-substituted poly(p-phenylene vinylenes), Macromolecules, 34 3716-3719, 2001. 

---