Converted photon energy

Photoelectrochemical semiconductor cells are used to convert photon energy into chemical substances or into electricity, the former is a photodectrolytic cell and the latter is a photovoltaic cell. A photoelectrochemical semiconductor cell consists of either a pair of metal and semiconductor electrodes or a pair of two semiconductor electrodes. 

PV cells convert photon energy into electrical energy. Two conditions must exist inside a PV material to for a PV electricity generation to occur (1) incident light energy must be sufficiently high to break a chemical bond in the material and thus create a free electron/hole pair and (2) an electrical asymmetry in the form of a p-n junction must be present [3],... 

There are three principal modes of ET, namely, thermal, optical and photoinduced ET, and these are shown schematically in Fig. 1. Optical ET differs from photoinduced ET in that ET in the former process results from direct electronic excitation into a charge transfer (CT) or intervalence band, whereas photoinduced ET takes place from an initially prepared locally excited state of either the donor or acceptor groups. Photoinduced ET is an extremely important process and it is widely studied because it provides a mechanism for converting photonic energy into useful electrical potential which may then be exploited in a number of ways. The most famous biological photoinduced ET reaction is, of course, that which drives... 

The light-induced isomerization of the azobenzene moiety is a classical example of controlled molecular motion and has provided the basis for the construction of some of the first archetypes of molecular machines [17]. In system 5, the pendant-arm/ring interaction concurs to improve the efficiency of the azobenzene-based engine, which converts photonic energy into a mechanical work, at the molecular level. 

Iron-thiazine photogalvanic cells use the photoredox reactions of Fe(II) with thiazine dyes, represented for thionine by Reactions 1, 2, 3, 4, and 5, to convert photon energy into chemical potential. The spontaneous ground state reactions represented by Reactions 6, 7, 8, and 9 also occur in homogeneous solution during illumination. Photogalvanic action results when homogeneous Reactions 7, 8, and 9 are replaced by anodic oxidation of and TH2 coupled with cathodic reduction of... 

Numerous luminescent compounds were demonstrated for their potential uses as centers/catalysts for photochemical syntheses — syntheses catalyzed by light (see also photochemical techniques and supramolecular photochemistry). Catalysts for photochemical reactions and syntheses are devices that convert photon energy to chemical energy (Fig. 4). In order to achieve a working photochemical... 

The advantage of T102 as a semiconductor photocatalyst comes from its ability of converting photon energy into chemical energy. The absorption of photons... 

Laser cutting is a thermal process converting photon energy, condensed into a very small spot, into heat. To clarify the scope of this chapter, detailed descriptions of all the components of a laser system cannot be given in here. Furthermore, all the statements refer to the CO2 gas laser representing the vast majority of the applications in metal cutting. However, most of the general descriptions also apply to solid-state lasers. 

On the other hand, single-wall CNTs (SWCNTs) can efficiently absorb and convert photon energy into thermal energy and have excellent thermal conductivities. Thus, they can act as a nanoscale heat source and thermal conduction pathway to heat the crosslinked LCP matrix effectively [51]. Furthermore, the resultant crosslinked PLCP/SWCNT nanocomposites exhibited effective photoactuation not only by white light but by near-IR irradiation as well [52]. Such nanocomposites were used to direct sun-driven artificial heliotropism for solar energy harvesting [53]. 

These data are typical of lasers and the sorts of samples examined. The actual numbers are not crucial, but they show how the stated energy in a laser can be interpreted as resultant heating in a solid sample. The resulting calculated temperature reached by the sample is certainly too large because of several factors, such as conductivity in the sample, much less than I00% efficiency in converting absorbed photon energy into kinetic energy of ablation, and much less than 100% efficiency in the actual numbers of photons absorbed by the sample from the beam. If the overall efficiency is 1-2%, the ablation temperature becomes about 4000 K. 

An incident ion beam causes secondary electrons to be emitted which are accelerated onto a scintillator (compare this with the operation of a TV screen). The photons that are emitted (like the light from a TV screen) are detected not by eye but with a highly sensitive photon detector (photon multiplier), which converts the photon energy into an electric current. 

Charge generation. Once the light is within the volume of the photosensitive material, the photon energy must be absorbed and converted to charge. The photon energy creates electron-hole pairs. 

When a nuclear event takes place, some rest mass is converted to extra mass of the product particles because of their high speed or to the mass of photons of light. While the total mass is conserved in the process, some rest mass (that is, some matter) is converted to energy. 

For chemical systems of interest, photolysis produces intermediates, such as radicals or biradicals, whose energetics relative to the reactants are unknown. The energetics of the intermediate can be established by comparison of the acoustic wave generated by the non-radiative decay to create the intermediate, producing thermal energy , with that of a reference or calibration compound whose excited-state decay converts the entire photon energy into heat, / (ref). The ratio of acoustic wave amplitudes, a, represents the fraction of the photon energy that is converted into heat. 

When the sunlight strikes the semiconductor material, an electrical potential is created by dislodging electrons due to the impact of the photons. Sunlight is made of photons that contain different amounts of photon-energy at different frequencies. The semiconductor material cannot readily be matched to convert all types efficiently. This means that some photons will not be converted at all because they have too little photon energy and some photons will only have a part of their energy converted to electricity because they have too much photon energy. 

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