Bio-hybrid Photovoltaic devices operated on living photosynthetic bacteria

The use of the abundant and easily available solar energy is central towards a carbon-free society and represents the most sustainable strategy for the increasing energy demand. Rhodobacter (R.) sphaeroides is a versatile photosynthetic purple non sulfur bacteria able to harvest sunlight, particularly in the Near InfraRed (NIR) region, and to efficiently transform it into photochemical energy. In this work, whole wild-type, metabolically-active photosynthetic bacterial cells of R. sphaeroides, and their carotenoid-less mutant strain, were integrated in a two-electrode architecture, to output a positive photovoltage upon illumination. The photovoltage amplitude of the mutant strain is almost three times higher than that obtained with wild-type cells. Photosynthetic bacteria were also integrated in a light-electrolyte-gated organic transistor to produce a photomodulated electronic current, as well as in a biophotonic power cell working on direct sunlight. This proves that bio-organic hybrid optoelectronic devices may enable environmentally safe and cost-effective energy production.