Codoping

Fig. 4 shows PL spectra of Mn and Pr-codoped ZnS nanoparticles opdcaily aimealed in air and vacuum. Mn and Pr-codoped ZnS nanoparticles emit light of white color. The PL intoisity of the Pr-related peaks incirasrf more rapidly than that of Mn-related peak, for the codoped ZnS nanoparticles ann ed in air. The different rates may be assodated with the luminescent ions. Pr-related oimplaces are incaeased with the incrrasing UV irradiation time, but Mn ions are constant. In case of the arni ing in vacuum, Pr-related peaks are initially weaker in intensity than Mn-related peaks due to small Pr-related complexes. 

Undoped, Mn, and Pr-doped ZnS namopartides synthesized by wet chemiral mdhod were optically annealed in air or vacuum. PL emission inoeas with annulling time. This increase is attributed to the photo-oxidation, enhancanent in the crystal quality, and diffiision of the luminescent ions. PL intensity of nanoparticles annealed in air increased more significantly due to the photo-oxidation compared with the nanoparticles annealed in vacuum. Mn and Pr-codoped ZnS nanoparticles emitted white light due to the effects of dopants. The optical annealing enhanced the emission intensity. 

Consider first blue sapphire Al203 Ti(III), Fe(III) (Fig. 2). In the absence of Fe(III) the absorption spectrum is easy to interpret. The weak band with a maximum at about 500 nm is due to the t2 —> e crystal-field transition on Ti(III) (3d ), the strong band at 2<280nm is due to a Ti(III)-0( — II) LMCT transition. The absorption band in the region around 700 nm in the case of the codoped crystal cannot be due to Fe(III). It has been ascribed to MMCT, i.e. to a transition within an iron-titanium pair ... 

Sun, X., Liu, H., Dong, J., Wei, J., and Zhang, Y. (2010) Preparation and characterization of Ce/N-codoped Ti02 particles for production of H2 by photocatalytic splitting water under visible light. Catalysis Letters, 135 (3-4), 219-225. 

Long, R. and English, N.J. (2010) Synergistic effects on band gapnarrowing in titania by codoping from first-principles calculations. Chemistry of Materials, 22 (5), 1616-1623. 

Another issue with ScSZ is that there is a decrease in conductivity at around 580°C as indicated by broken lines in two of the curves for higher scandia contents, 10.0 to 12.0 mol%. With high scandia contents, the cubic phase transforms to a lower conductivity rhombohedral phase, the p phase, at lower temperatures [25], The phase change can be avoided by limiting the scandia content to 8 mole% [25] or by codoping with other oxides, such as those of bismuth [36] or ytterbium [37],... 

Codoping has been used to improve the electrochemical properties, chemical stability, thermal stability, or decreasing the cost of Ln3+ as a stabilizer. Usually,... 

Lei and Zhu [63] found that adding 2.0 mol% Mn203 to llScSZ can inhibit the cubic-rhombohedral phase transformation in both oxidation and reduction atmospheres, and the codoped zirconia can reach nearly full density when sintered at temperatures as low as 850°C. The conductivity of 2Mn203-l IScSZ sintered at 900°C is 0.1 Scm-1 at 800°C. Figure 1.11 illustrates the conductivity of some zirconia-based ternary systems [32,42,57,63-67],... 

FIGURE 1.32 Effect of Sm-doping content on the conductivity in air for codoped ceria with nominal composition of SmyGd015.yCe0.85O1 925 [132,133]. 

FIGURE 1.33 Effect of Sm-doping concentration (y) on the activation energy (Ea) of conduction for codoped ceria of SmyGd015 yCe0925 [132,133]. 

FIGURE 1.34 Comparison in open-circuit voltage of a unit cell with gadolinia-doped ceria electrolyte containing 3 mol% of Ln(Y, Sm, Nd, Pr, and La) codopant [134]. 

Codoped Single Doped Effect on Conduction Behaviors... 

Same as arylamine DSA derivatives used as guest materials in blue OLEDs, Geise et al. synthesized a series of alkyloxy-substituted biphenyl vinyl compounds as dopant materials [236]. These authors studied OLEDs fabricated using PVK as a host polymer and holetransporting PBD as a codopant with a PLED structure of ITO/PEDOT-PSS/PVK 230VBP PBD/LiF/Al, which gave an optimized QE of 0.7% and brightness of 1600 cd/m2 at 100 mA/cm2 with emission peak at 450 nm. 

White emission can also be achieved by directly combining a blue emitter and an orange-red emitter as codopants. The combination of blue and orange-red emission generates white emission. 

In comparison to the research in n-type oxide semiconductors, little work has been done on the development of p-type TCOs. The effective p-type doping in TCOs is often compensated due to their intrinsic oxide structural tolerance to oxygen vacancies and metal interstitials. Recently, significant developments have been reported about ZnO, CuA102, and Cu2Sr02 as true p-type oxide semiconductors. The ZnO exhibits unipolarity or asymmetry in its ability to be doped n-type or p-type. ZnO is naturally an n-type oxide semiconductor because of a deviation from stoichiometry due to the presence of intrinsic defects such as Zn interstitials and oxygen vacancies. A p-type ZnO, doped with As or N as a shallow acceptor and codoped with Ga or Zn as a donor, has been recently reported. However, the origin of the p-type conductivity and the effect of structural defects on n-type to p-type conversion in ZnO films are not completely understood. 

The fluorescence lifetime of Eu + in fluorite (CaF2) crystals is 700 ns. When these crystals are codoped with Sm + ions, the lifetime of the Eu + ions is reduced to 150 ns. Determine the energy transfer rate from the Eu + ions to the Sm + ions. 

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