A plausible mechanism in premicellar aggregates for photocurrent generation in photogalvanic cell for simultaneously solar power conversion and storage

Abstract

Photogalvanic (PG) cells are the only solar cell that can convert and store solar energy simultaneously. The PG cell is based on the diffusion of electrolytes (dye, reductant, alkali/acid and surfactant). We have completed photogalvanic study for the four (BCB-fructose, BCB-AA, MB-fructose and MB-AA) redox systems without and with SDS, CTAB and tween 80 surfactant in our previous research work. The results show that the most efficient system is MB-AA-SDS, in which methylene blue (MB) as a photosensitizer, ascorbic acid (AA) as reductant, and sodium dodecyl sulphate (SDS) as anionic surfactant is used. Since, to make an efficient cell, it is very important to understand the mechanism part. Consequently, the aim of this paper is to provide information about the basic difference of photocurrent generation in PV, DSSC and the PG cell, a plausible mechanism for the generation of electricity in the PG cell having MB, AA and SDS, and also give mechanism for stabilization of MB molecules in premicellar region of SDS on the basis of findings of our previous research work and literature study. For the same, first, made a comparative study for generation of electricity in PV, DSSC and the PG cell, then the most possible mechanism for photocurrent generation in PG cell and lastly mechanism for solubilization and stabilization of the MB molecules by SDS have been given. The comparative study of different solar cells shows that the basic principle for conversion of solar to electrical energy is same for all solar cells. The main difference is in the place of chemical reactions which occur on the surface of the electrode in solar cells while in the PG cells, it occurs inside the electrolytic solution. The AA/ascorbate ion and the base form of the MB are stabilized by premicellar aggregates of SDS, this helps to solubilize the MB molecules by providing an ordered way and enhancing the number of MB molecules for absorption of light in the PG cell. This ultimately enhances the number of leuco forms of MB which leads to an increase in the number of electrons in the external circuit of the PG cell. Thus, by understanding the most plausible mechanism one can make a PG cell in which the compatibility of surfactant is maximum with a dye-reductant system for photocurrent generation and storage, simultaneously. Further, it provides basic ideas about conditions and parameters which are responsible for the better electrical output of the PG cell. This may make the cell practically viable for daily life in the future.