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Cathode quantum efficiency

The RCA C313034 with a GaAs cathode has a cathode quantum efficiency far better than that of the S-20 type in the red region. This photomultiplier tube allows the study of the 2700-3200 cm-1 Raman shift region with greater sensitivity using the red line (Fig. 8). [Pg.314]

Figure 13-13. (a) Currem-vollage data from MEH-PPV-bascd OLEDs willi Au anodes and various cathodes plotted according to E4. (13.5) (b) the external quantum efficiency for the diodes with Al and Ca cathodes The solid line represents the maximum efficiency of 2%. Reproduced with permission from 11511. Copy light 1998 by the American Physical Society. [Pg.234]

Similar results of photoelectrolysis of water in cells with n-type SrTi03 single-crystal anode and platinized Pt cathode were reported around the same time in a preliminary communication by Mavroides et al. [53] who measured the maximum quantum efficiency... [Pg.247]

A p-type electrode is in depletion if a cathodic bias is applied. Illumination generates one electron per absorbed photon, which is collected by the SCR and transferred to the electrolyte. It requires two electrons to form one hydrogen molecule. If the photocurrent at this electrode is compared to that obtained by a silicon photodiode of the same size the quantum efficiencies are observed to be the same for the solid-state contact and the electrolyte contact, as shown in Fig. 4.13. If losses by reflection or recombination in the bulk are neglected the quantum efficiency of the electrode is 1. [Pg.66]

While the external quantum efficiency of PS reported for solid-state contacts is usually low, wet contacts are found to give high EL efficiencies at low applied bias under anodic [Vi2, Itl, Ge2, Ha7] as well as cathodic conditions [Bsl]. An example of bright EL from a micro PS sample in acetic acid under anodic bias is shown... [Pg.148]

An optical microcavity produced by the latter process has been applied to tune the emission from erbium-doped PS [Zh6], Erbium compounds like Er203 are known to exhibit a narrow emission band at 1.54 pm, which is useful for optical telecommunications. Several methods have been used to incorporate erbium in PS. A simple and economical way is cathodic electrochemical doping. External quantum efficiencies of up to 0.01% have been shown from erbium-doped PS films under electrical excitation [Lo2]. The emission band, however, is much broader than observed for Er203. This drawback can be circumvented by the use of an optical cavity formed by PS multilayers. In this case the band is narrowed and the intensity is increased because emission is only allowed into optical cavity modes [Lo3]. [Pg.228]

Figure 12.21. Photocathode spectral sensitivity curves in imlliampcres of cathode current per watt ofradiam power falling on the photocathode, q is the photocathode quantum efficiency, i.e, the probability of photoelectron emission (Adapted from Ref 76.)... Figure 12.21. Photocathode spectral sensitivity curves in imlliampcres of cathode current per watt ofradiam power falling on the photocathode, q is the photocathode quantum efficiency, i.e, the probability of photoelectron emission (Adapted from Ref 76.)...
Another type of Chi interfacial layer employed on a metal electrode was a film consisting of ordered molecules. Villar (79) studied short circuit cathodic photocurrents at multilayers of Chi a and b built up on semi-transparent platinum electrodes in an electrolyte consisting of 96% glycerol and 4% KCl-saturated aqueous solution. Photocurrent quantum efficiencies of multilayers and of amorphous films prepared by solvent evaporation were compared. The highest efficiency (about 10 electrons/ absorbed photon, calculated from the paper) was obtained with Chi a multilayers, and the amorphous films of Chi a proved to be less efficient than Chi b multilayers. [Pg.243]

We have investigated the photocurrent behavior of multilayers of a Chi a-DPL (molar ratio 1/1) mixture on platinum in an aqueous electrolyte without added redox agents (80). Cathodic photocurrents with quantum efficiencies in the order of 10- were obtained with films consisting of a sufficient number of monolayers. The photocurrent was increased in acidic solutions. However, no appreciable photocurrent was observed with a single monolayer coated on platinum. The latter fact most probably results from minimal rectifying property of the metal surface and/or an efficient energy quenching of dye excited states by free electrons in... [Pg.243]

Tetraphenylporphine (TPP) and other metal porphyrine derivatives coated on platinum (87,88,89) or gold (89,90) electrodes have been investigated in photoelectrochemical modes. Photocurrents reported are cathodic or anodic, depending on the pH as well as the composition of the electrolyte employed. Photocurrent quantum efficiencies of 2% (89) to 7% (87) were reported in systems using water itself or methylviologen as the redox species in aqueous electrolyte. Photocurrent generation at Zn-TPP-coated metal cathodes (89) was interpreted in terms of a rectifying effect of the Schottky barrier formed at a metal-p-type... [Pg.244]

Bilayered polysilane LEDs have been obtained by inserting a SiOx thin layer between the cathode and a Wurtz synthesized PMPS emitter film.94 The SiOx layers were prepared by 02 plasma treatment of the PMPS film surfaces. It was found that the external quantum efficiency was significantly enhanced by this treatment. This enhancement has been attributed to an increased electron injection via tunneling, resulting in a reduced hole current caused by the blocking effect of the thin SiOx layer. The weak visible emission observed from single-layer polysilane LEDs is almost completely eliminated. It was concluded that the visible emission is caused by the erosion of the PMPS surfaces due to the collision with hot metal particles during the vacuum deposition of the cathode, and this erosion process is avoided by the SiOx layer. [Pg.232]


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