Harvesting solar energy with man-made leaves

06-Nov-2013 - Japan

Scientists in Japan have developed a two-step artificial photosynthetic process that mimic’s nature’s efficient method for harvesting energy from sunlight by using a system of a large number of artificial leaves, as plants do.

The researchers used a large number of light absorbers to relay photons via a small number of antennae into one final energy acceptor, resulting in greater and more efficient energy transfer. Until now, researchers have only used single-step light harvesting systems, which greatly limit the number of absorbers able to feed light into a single reaction centre.

The team combined 440 periodic mesoporous organosilica (PMO) tubes bridged by light-absorbing biphenyl (Bp) groups with five stick-shaped rhenium (I) pentamer units connected to one ruthenium(II) trisdiimine complex (Ru-Re₅). This Ru–Re₅–Bp–PMO hybrid system concentrates photons absorbed by the large framework of Bp–PMO in two steps: first to the rhenium oligomers, and then to the ruthenium reaction centre.

Tokyo Institute of Technology professor, Osamu Ishitani, who led the research, said: “Photon collection has always been a problem in developing efficient solar energy conversion systems because the molecules are so small and solar light is so dilute. This new system is fantastic because now we can accumulate light from a large area and into, say, a photocatalyst.”

The research team plan to merge this light harvesting technique with their work on photocatalysts for CO₂ reduction, with an eventual application in water oxidation photocatalysis.