Sandwich cells

A textbook example for the successful application of the model of Arkhipov et al. is the work of van Woudenbergh et al. [173]. More recently, Agrawal et al. [106] compared injection limited currents and space-charge-limited currents in a copper-phthalocyanine sandwich cell with TTO and Al electrodes. An analysis of experimental data yields consistent values for the width of the DOS distribution as well as for inter-site separation [174]. These studies support the model of thermally activated injection into a Gaussian DOS distribution of hopping sites and confirm the notion that disorder facilitates injection because it lowers the injection barrier, although the transport velocity decreases with increasing disorder. 

Figure 1.5 (a and b) Typical electrode configurations used for the measurements of thermally stimulated currents. The sample surface ceU (a) may be augmented by additional contacts (b)-(d) to monitor potential distribution along the sample. The sandwich cell (e)-(h) is ideally suited for the use of guard rings of either rectangular or circular shapes. 

It has recently been shown that organic photoconductor-liquid crystal sandwich cells can in theory act as dynamic scattering devices 164> and the technical possibilities ought to be tested. In this context, it should be noted that dyes can be used in two-layer photocondensers (consisting e.g. of phthalocyanine and a ferroelectric ceramic), which are very sensitive to light and have a response time of lO-4 to 10-3 Sec 165). 

Figure 17.32 Photoaction spectra obtained in presence of Cu(I)/Cu(II) electron mediators using regenerative sandwich cells equipped with gold counter electrodes. (5) Stars, (1) open circles, (4) open triangles, (2) solid triangles, (3) open squares, and (6) solid circles. Data compared with the F/I3 couple (black squares). Li+ 0.5 M was added to all copper-based electrolytes.

Tbpy increases the open-circuit photovoltage via suppression of the back recombination. With such a treatment, FT O/T i 02/dy e/P E D OT-P E D /FT sandwich cells afforded efficiencies of the order of 2.6%, one of the highest results so far recorded with solid-state DSCs based on hole conducting polymers (Fig. 17.46). 

Fig. 7. Systems for photoconductivity and mobility measurements, a) sandwich cell, b) surface cell...

Fig. 9 Structure of sandwich cells for measurement of photoswitching of hole injection, (a) metal-diarylethene-Au, (b) ITO-diarylethene-organic hole transport layer.

The solar to electric power conversion efficiency of dye-sensitized solar cells of laboratory scale (0.158 cm2), validated by an accredited photovoltaic calibration laboratory, has reached 11.1% under standard reporting conditions, i.e., air mass 1.5 global sunlight at 1000 Wm-2 intensity and 298 K temperature, rendering it a credible alternative to conventional p-n junction photovoltaic devices [68]. Photovoltaic performance data obtained with a sandwich cell under illumination by simulated AM 1.5 solar light using complex 26 are shown in Fig. 16. At 1 sun the 26-sensitized solar cell exhibited 17.73 =b 0.5 mA current, 846 mV potential, and a fill factor of 0.75 yielding an overall conversion efficiency of 11.18%. 

Figure 3-19 Resonance Raman spectroelectrochemistry cells and back scattering geometry. (A) Controlled potentional electrolysis cell (B) sandwich cell for semi-infinite diffusion conditions. (Reproduced with permission from Ref. 73. Copyright 1975 American Chemical Society.)...

The major difference between the configuration of the OMI sandwich cell and other STN-LCDs is that the optical path difference (5 = And 1 pm) is much lower. There is no requirement for a significant pretilt (0 < 0 < 5°), the twist angle of the chiral nematic layer is lower (180°), the front polariser is parallel to the nematic director (a = 0°) and the polariser and analyser are crossed (P = 90°). The 180° twist gives rise to strong interference between the two elliptically polarised rays. If the optical path difference is small, e.g. 0.4 m, a bright, white, non-dispersive off-state is produced. The chiral nematic mixture should be of positive dielectric anisotropy, low birefringence and exhibit a low cell gap to pitch ratio dip 0.3). 

The electrode surfaces of a normal LCD sandwich cell d 8-10 pm) are coated with an alignment layer in order to induce a planar alignment of a host (chiral) nematic mixture containing the dichroic dye of positive dichroism and a chiral dopant. Due to the absence of polarisers a very thin mirror can be incorporated within the cell on top of the rear glass plate electrode in direct contact with the guest-host mixture, see Figure 3.15. 

Particularly when doped appropriately, the ionic liquid fuel cell (ILFC) gives clearly superior performance [18]. Using an ambient temperature version of the (technologically unacceptable) difluoride IL illustrated in Figure 2.8, equally good performance can be obtained at ambient temperature It is expected that this application of the ionic liquid concept will receive considerable attention in the immediate future. Results using more efficient Teflon sandwich cells and colloidal Pt electrodes will be reported separately [41]. 

Pulsed photoconductivity provides a powerful means of measuring carrier mobilities. The usual experimental arrangement shown in Fig. 4.8 (Kepler,1960) uses a sandwich cell with a transparent front electrode. If the coefficient of... 

Figure 7.13 SEM images of the surface of PSC annealed at 1500 °C in a vacuum chamber (a), and at 1700 °C in the sandwich cell (b)...

Adapter, T type, 24/40 Adapters, hose connection with stopcocks, 24/40 joints, one inner, one outer Beaker, 30 mL Beaker, plastic, 400 mL Bottles, wash, 250 mL Card, calibration, polystyrene Cell, NaCl, sandwich Cell, NaCl, wedge Clamps, buret... 

Place an NaCl sandwich cell on a paper or cloth towel. CAREFUL NaCl rapidly dissolves in water - do not breath on this cell or expose it to any water. 

Place chloroform in either a second sandwich cell or a wedge cell and place this cell in the reference beam of the instrument. 

The design of sandwich cells (FIGURE 3) is defined, firstly, by the direction of mass transfer. In the upper part of the crucible the material transport occurs upwards and the substrate is mounted on a graphite or tantalum holder. Polycrystalline SiC powder is the most... 

FIGURE 2 The positioning of silicon sources and of sandwich cells with respect to the temperature field... 

FIGURE 3 The modifications of sandwich cells employed for the growth of SiC (a) with powder SiC source, (b) with dense polycrystalline SiC source, (c) with single crystal source. 

Quite pronounced photovoltaic effects have been observed in Mx 1150 nm -chlorophyll a M2 sandwich cells, where Mx = A1 or Cr and M2 = Hg or Au.7e>77 These are ascribed to a Schottky barrier at the junction with metal Mx which has a lower work function than M2. If the Mi junction is the front (illuminated) electrode then the photovoltaic action spectrum is identical with the absorption spectrum of the chlorophyll. If it is at the rear, the action spectrum shows an inner filter effect, because only light absorbed in the region of the barrier is effective. Figure 11 shows the performance of a typical cell, which has a power conversion efficiency of ca. 10-3% at 745 nm. The best efficiency, 5 x 10-a%, was achieved by a Cr chlorophyll a Hg cell. Photovoltaic properties have also been reported in the cell A11 Mg phthalocyanine Ag, which has a Schottky barrier of height ca. 0.6 eV at the A1 junction.78 At 690 nm, the power conversion efficiency was ca. 10-2%. It has been shown that oxidized A1 contacts to Cu phthalocyanine are blocking.79... 

---