Illuminated characteristics

The illuminating characteristic of the flare is only partly determined by the thermal radiation from the oxide particles, a second factor being the spectral emission from excited metals. 

Fig. 5.18. Measurement and simulation of a bulk heterojunction solar cell in the dark (a) and under illumination (b). The dark I/V characteristics are plotted semi-logarithmically, whilst the illuminated characteristics are plotted on a linear scale. The bulk heterojunction was simulated as a diode with the following structure positive electrode/p++/i/n++/negative electrode, (c) Local variation of the energy levels (top) and of the carrier densities for a bulk heterojunction solar cell with balanced mobilities, (d) Local variation of the energy levels (top) and of the carrier densities for a bulk heterojunction solar cell with higher electron mobility...

The dark and illuminated characteristics of the PCBM PPV solar cells for different concentrations of PCBM are shown in Fig. 5.18. It can be seen that the dark characteristics are not described by Shockley type equation. Forward illuminated I(V) curves are strongly dependent on the applied voltage. Under reverse bias the illuminated current is not so sensitive to the voltage. 

Brabec and coworkers have made extensive measurements of the dark and illuminated currents of MDMO-PPV/PCBM BHSCs [124,141], The experimental results for the BH-SCs from their paper [124] are shown in Fig. 5.22. There are points of inflexion in the dark current of the organic solar cell confirming that the dark current is the space charge limited currents. These features, particularly the points of inflexion, are absent in the illuminated characteristics. At larger voltages the forward dark current intersects the illuminated current and the illuminated current becomes larger than the dark current. 

SCLC is bulk control in these materials, it can not yield any information about the built-in voltage at the contact or at the junction. Han et al. [147] showed that the illuminated characteristics closely obey Eq. (5.8) as shown in Fig. 5.24(b). 

Illuminating Characteristics with Variation in Component Ratio... 

Under Irradiation. Under illumination, the surface characteristics can undergo dramatic changes, altering the nature of the adsorption sites. Thus, dark adsorption—desorption events are altered, and additional events arising from photoadsorption—photodesorption equiUbria take place. 

Impairment of visibility involves degradation of the ability to perceive the environment. Several factors are involved in determining visibility in the atmosphere (Fig. 10-1) the optical characteristics of the illumination source, the viewed targets, the intervening atmosphere, and the characteristics of the observer s eyesight (1). 

Another important characteristic of XPS is that relatively little damage occurs when samples are illuminated with X-rays, especially from a non-monochromatic... 

Figure 15-20. Currenl versus voltage characteristics of the lTO/MEH-PPV/C Au device in the dark (diamonds) and upon illumination wilh the 514.5 nm line of argon-ion laser of 1 mW/cm2 (triangles) (reproduced by permission of the American Institute of Physics from Ref. 1891).

Figure 15-30. t/V characteristics of small area glass cell ( dark - illuminated with 488 mil. 10 mW/cm2) and a flexible large area... 

Figure 15-31. l/V characteristics of a large area plastic solar cell ( illuminated with 488 nm, 10 rnW/ cm2). FF for the 1TO plastic cell is 0.35. As reference a pholocurrcnl of a polycrystalline Si cell is plotted ( ), 10 limes reduced. 

Figure 15-27. Currcnl-vollagp characteristic of a Ca/MEH-PPV 16,6 PCBM/1T0 device in the dark (open circles) and under 20 mW/on2 illumination at 430 mu (solid circles) (reproduced by pennission of the American Association lor the Advancement of Science from Ref. [5 ).

For this study, thin films were deposited onto glass substrates. The as-deposited films showed no spectral narrowing at any pump energy up to the damage threshold. Stimulated emission was observed only in annealed films. The spol-to-spot reproducibiliiy of the measured characteristics was good, and we could measure with excitation energies of up to 4 mJ (1.8 mm beam diameter) without visual damage of the illuminated spot. 

The indirect methods discussed thus far have dealt with measurement of color only as it can be correlated with physical characteristics of materials and the effect of these materials on radiant energy. As has been pointed out, the reflectance spectro-photometric curve describes a property of the material. A change in the reflectance spectrophotometric properties may not always result in a change in visual color. The reason is that color of the object is not an unchangeable characteristic of the object itself, dependent only upon these reflectance properties, but is also dependent upon the quality of the illuminating light and the sensitivity of the observer s eye. Thus the measurement and description of visual color are psychophysical problems... 

FIGURE 1.15 When a metal is illuminated with ultraviolet radiation, electrons are ejected, provided the frequency is above a threshold frequency that is characteristic of the metal. 

Besides improvements in catalyst characteristics [28], the low productivity of a photocatalytic process can also be improved by reactor design. In photocatalytic research on a laboratory scale, the most widely applied reactors are the top illumination or annular reactors containing a suspended catalyst [29]. This type of... 

When porphyrins dissolved in strong mineral acids or in organic solvents are illuminated by ultraviolet hght, they emit a strong red fluorescence. This fluorescence is so characteristic that it is often used to detect small amounts of free porphyrins. The double bonds joining the pyrrole rings in the porphyrins are responsible for the characteristic absorption and fluorescence of these compounds these double bonds are absent in the porphyrinogens. 

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