Light energy conversion with chlorophyll a and pheophytin a monolayers at the optically transparent SnO₂ electrode: artificial photosynthesis

The photoelectrochemical behavior of chlorophyll a and pheophytin a monolayers, deposited on tin oxide (SnO₂) optically transparent electrodes (OTE) by means of the Langmuir-Blodgett technique, has been investigated. The photocurrent action spectra coincide with the absorption spectra of photosynthetic pigment monolayers at the SnO₂/solution interfaces. Anodic and cathodic photocurrents were measured at various electrode potentials. Effects of electrolyte concentration, pH, electrode potentials, type of SnO₂ OTE and the nature of redox reagents on the magnitude of the photocurrent in solar energy conversion are discussed. A mechanism for the electron transfer in thin films of photosynthetic pigments in monolayers at the SnO₂ OTE is proposed. On the other hand, the absorption and fluorescence spectral characteristics, and fluorescence lifetime measurements of pheophytin a in monolayers and thin films are also discussed in view of the aggregation properties of the photosynthetic pigments.