Photovoltaic properties of mixed monolayers of chlorophyll a and carotenoid canthaxanthin

Abstract

Photovoltaic studies of cells of the type (Al|pigment monolayers|Ag) prepared by sandwiching the mixed monolayers of chlorophyll (Chl) a and the carotenoid canthaxanthin (Cantha) between electrodes of Al and Ag have been made. The cells (Al|Cantha monolayers|Chl a monolayers|Ag) do not show any photocurrent, while photocurrent for cells (Al|Chl a|mixture of Chl a and Cantha|Chl a|Ag) has been observed. This has been explained in terms of the characteristics of metal|semiconductor junction. The action spectra of the cells have been found to resemble the absorption spectra, which indicates that the singlet excitons are the precursors of the charge carriers. The appearance of photocurrent in absorption region of canthaxanthin is suggested to be due to the energy transfer from canthaxanthin to Chl a.