Power density, light

The relative edge power density is the output in mW/cm2 from the edge of radiant power at the emission wave-length under illumination by an incident (white light) power density of 100 mW/cm2 (=1 kW/m2) under AM 1 conditions. 

Fig. 1 Matching of current-voltage characteristics of solar cell and electrolyzer (a) at constant light power density 1, 2, 3 - characteristics of solar cell at Ng = 1,2, and 4 (at Sj = const) 4 - characteristic of electrolyzer (Ng = 1) o - maximum power point (MPP) dashed line shows the locus of maximum cell output power at the given radiation power density (b) at varying radiation power density 1 , 2, 3, -characteristics of solar cell dashed line - locus of MPP hatched area - variations of MPP in the most probable limits of variation of the light power density and temperature 4 - characteristic of electrolyzer.

In Eq. (1), / is the maximum current that can run through the cell. The open circuit voltage (V ) depends on the highest occupied molecular orbital (homo)level of the donor (p-type semiconductor quasi Fermi level) and the lowest unoccupied molecular orbital(lumo) level of the acceptor (w-type semiconductor quasi Fermi level), linearly. P in is the incident light power density. FF, the fill-factor, is calculated by dividing P by the multiplication of / and V and this can be explained by the following Eq. (2) ... 

Fig. 1.41 (a) Relation between the incident light intensity and the frequency up-converted iight intensity, (b) Illustration of the two-step excitation and subsequent light emission, (c) Efficiency of the frequency up-conversion as a function of the incident light power density. For comparison, the efficiency of the second harmonic generation from a KDP crystal is tilso shown... 

Here I is the intensity of incident light, L is the thickness of the photoconductor, a is the absorption coefficient, and X is the wavelength of light. If /ph is the photocurrent, Po is the light power density, A is the illuminated area, and V is the applied voltage, the change in conductivity per incident light intensity, called... 

The efficiency of the cell is the power density delivered at operating point as a fraction of the incident light power density,... 

Luminance is the luminous intensity divided by the area of emission of light (Iumens/steradian/m2). This is the power density emitted per unit area. 

Various names for this allotropes were in use intermediate phase sulfur (ip-S) [184], high-pressure unknown phase (HPU phase) [191], and photo-sensitive or, more recently, photo-induced sulfur (p-S) [57, 58, 119, 186], respectively. We are inchned to make use of the term photo-induced since it has clearly turned out that the formation of this allotrope is induced when employing laser light of suitable power density and wavelength [1]... 

FIG. 62. Normalized solar cell efficiency as a function of illumination time for different power densities as obtained by continuous illumination of 1000-W/m" AM 1.5 light. The initial efficiencies of the four cells were 9%, 109f. 9c. and 69c for 28-. 42-. 57-. and 113-mW/cm power density, respectively. 

One of the main characteristics of the laser emission is the huge amount of energy that is concentrated within a narrow beam and can be delivered on a tiny area. In order to take full profit of the high power density available, it is also necessary to use photosensitive systems which obey the reciprocity law, i.e. where the energy required for the reaction is not dependent on the light intensity, which means that the quantum yield remains constant. This condition appears to be almost fullfilled in the present case since the fluence, expressed in J cm-2, was found to increase by only a factor of 4 when the light-intensity was increased by over 4 orders of magnitude (Table I). 

Figure 8.3 The similarity of the EEG effects of 12 h total sleep deprivation (TSD) and 0.5mg/kg MK-801. Standardized power density functions for the 12 h light period are shown for the frequency ranges most affected by the two treatments. Both TSD and MK-801 increased power in the 1-4 Hz frequency band during NREM sleep and the 10-20 Hz frequency band during REM sleep. (A) MK-801 vs. saline, NREM (B) MK-801 vs. saline, REM (C) 12 h TSD vs. control, NREM (D) 12 h TSD vs. control, REM.

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