Photogalvanic effect

Koroteev N I 1996 Optical rectification, circular photogalvanic effect and five-wave mixing in optically active solutions Proc. SPIE 2796 227-38... 

After dark-condition equilibrium was established, as indicated by the visible spectra, the photo-shift in equilibrium was observed to be completely reversed when the illumination ceased. This photogalvanic effect maintained a mass balance in the system, with no reagent consumed or generated during the dark-light-dark cycle. This observation suggested that the plutonium system in the proper network of a concentration cell... 

The photogalvanic effect is based on light absorption by a suitable photoactive redox species (dye) in the electrolyte solution. The photo-excited dye subsequently reacts with an electron donor or acceptor process, taking place in the vicinity of an electrode, is linked to the electrode... 

The term photovoltaic effect is further used to denote non-electrochemical photoprocesses in solid-state metal/semiconductor interfaces (Schottky barrier contacts) and semiconductor/semiconductor pin) junctions. Analogously, the term photogalvanic effect is used more generally to denote any photoexcitation of the d.c. current in a material (e.g. in solid ferroelectrics). Although confusion is not usual, electrochemical reactions initiated by light absorption in electrolyte solutions should be termed electrochemical photogalvanic effect , and reactions at photoexcited semiconductor electodes electrochemical photovoltaic effect . 

The electrochemical photovoltaic effect was discovered in 1839 by A. E. Becquerelt when a silver/silver halide electrode was irradiated in a solution of diluted HN03. Becquerel also first described the photogalvanic effect in a cell consisting of two Pt electrodes, one immersed in aqueous and the other in ethanolic solution of Fe(C104)3. This discovery was made about the same time as the observation of the photovoltaic effect at the Ag/AgX electrodes. The term Becquerel effect often appears in the old literature, even for denoting the vacuum photoelectric effect which was discovered almost 50 years later. The electrochemical photovoltaic effect was elucidated in 1955 by W. H. Brattain and G. G. B. Garrett the theory was further developed... 

The photogalvanic effects are initiated by a homogeneous photoredox reaction of an electrolyte redox system with a suitable photoexcited organic or organometallic substance (dye), S. The photon absorption produces a short-lived, electronically excited dye molecule, S ... 

Electrodes can also play the role of electron acceptor and photogalvanic effects can be induced by anion excitation, eq. 

Nonetheless, sensitization by dyes held within the cores of microemulsions can be easily accomplished [69]. Such sensitization is an important component of photogalvanic effects, the magnitude of which are significantly enhanced in the non-homogeneous environment of a microemulsion [70], The hydrophilic core of an water-in-oil microemulsion can concentrate cation radicals formed via interfacial electron transfer and hence increase the yield of subsequent dimerization the dimethylnaphthalene cation radical exhibits a dimerization equilibrium constant of nearly 500 in a microemulsion [71]. For similar reasons, hexylviologen acts as a much more efficient relay than methyl viologen in a CTAB/hexanol microemulsion [72]. 

Finally, it should be noted that when the back electron transfer reaction between the primary products (At and A 2 in Fig. 13) is sufficiently slow, the concentrations of these products attain appreciable steady-state values. In such a case, a photogalvanic effect can be observed in the system (Section 8). 

E. Rabinowitch, The photogalvanic effect I. The photochemical properties of the thionine-iron system, J. Chem. Phys., 8, 551-559 (1940). 

Research into the photogalvanic effect has hardly progressed in recent years and the field is in urgent need of a fresh impetus. Irradiation of an acetonitrile solution of... 

Pittman R. W. (1953), The photochemistry of selenium. Part III. Photogalvanic effects with red selenium Part IV. Photogalvanic effects with grey selenium , J. Chem. Soc. 855-860, 3888-3893. 

Earlier light-to-electricity conversion cells were often based on the photogalvanic effect, whereby light was absorbed in a dye in solution or adsorbed on an elecnode surface. The iron-thionine cell of Murphy (1978) provides an example of a photogalvanic device with storage. The forward reaction is ... 

The corresponding current value is mainly determined by the back-reaction between S " and D". This kind of photocurrent is based on photochemical effects in solution and is also known as the photogalvanic effect, already reported in 1961 [59], Very large photocurrents have been obtained by using the leuco dye (SH2) as an electron donor. 

Protonated poly vinylpyridine (PVP) coated on Nesa glass bound rose bengal electrostatically. This modified electrode, when dipped into an aqueous solution containing a redox reagent such as Fe, induced an anodic photogalvanic effect A photo-... 

Rohatgi-Mukherjee KK, Choudhary R, Bhowmik BB (1985) Molecular interaction of phenosafranm with surfactants and its photogalvanic effect. J Colloid Interface Sci 106 45... 

Dube S, Sharma SL, Ameta SC (1997) Photogalvanic effect in azur B-NTA system. Energy Convers Manage 38 101... 

Fig. 21 An example of the use of Ru(bpy)32+ as LAS light energy is converted into electrical energy (photogalvanic effect).

The involvement of LES in electrochemical processes may allow the conversion of electrical energy into light. This phenomenon, which is the reverse of the previously described photogalvanic effect, is called electrochemiluminescence (ECL). One of the most noticeable examples of ECL is that concerning Ru(bpy)3 in acetonitrile solution [57,58]. When cyclic square waves between the potentials of formation of Ru(bpy)3" and Ru(bpy)3 (figure 8) are applied at a Pt electrode immersed in the solution, a red luminescence is observed which continues indefinitely if the electrical potential is maintained. The reaction mechanism, illustrated in figure 22 involves reactions (56) - (59) ... 

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