Energy effciency of the sunlight harvesting and storing system in bacterial photosynthesis: comparison with semiconductor photovoltaic cells

Abstract

The light phase of photosynthesis is considered a joint operation of 2 functional pigment protein complexes: a lightharvesting antenna, absorbing sunlight in a wide spectral range, and a reaction center, utilizing the energy of absorbed light quanta inphotochemical charge separation reactions. Tese complexes allow converting solar energy to the energy of specifc biomolecules withhigh quantum efciency. However, before being transferred to reaction centers, the solar energy is stored in the lowest excited state ofpigment molecules of the light harvesting antenna that partially convert light quantum energy into heat. Tese energy losses bring asignifcant reduction of energy efciency of photosynthesis in view of a very wide spectral range of photosynthetically active sunlight. Inthe current study we analyzed the energy efciency of sunlight harvesting and storing in diferent photosynthetic bacteria with diferentabsorption bands. We showed that simultaneous exploitation of several such photosynthetic organisms leads to an increased totalenergy efciency in terms of harvesting sunlight of the wider spectra. Maximal values of energy efciencies of the sunlight harvestingand storing system in photosynthetic bacteria and semiconductor photovoltaic cells are compared, and perspectives on practical use ofphotosynthetic bacteria as solar energy converters are discussed.