Solar Cells Imitate Photosynthesis

Green plants, algae, and some bacteria use sunlight to convert energy with the help of pigments in chlorophyll that absorb electromagnetic radiation, thereby initiating chemical reactions in electrons. These reactions are performed in the nucleus of complex protein structures known as photosystems I and II. Catalysts induce the processes that take place in these photosystems in a certain order. In the initial step, oxygen is released from water and the later reaction prepares the production of carbohydrates and no further source of energy is required in the reaction.

The reaction centers of the photosystems are surrounded by light-absorbing pigments that are grouped into consolidated complexes. These pigments increase the area available for light rays to hit and extend the spectrum of usable wavelengths. Now, a team of researchers from University of Erlangen-Nuremberg led by Prof. Dr. Dirk Guldi is focused on enhancing the productivity of solar technology. The team set to synthesize modules based on the correlation between structure and function in photosystem II. The new system includes light-absorbing crystals, transistors, and solar cells that are layered into a network of hexagonal honeycombs. The network is surrounded by a water-oxidising catalyst with four ruthenium metal atoms in the center. In a simplified manner, the compact, stable units made up of two components with a common long axis are reminiscent of cylindrical batteries. Such miniature power stations in the self-assembling chemical process develop two dimensional slats. These stations form a common block, which collects the energy absorbed from sunlight.

According to the researchers, although the system is not an entirely accurate reproduction of the ideal arrangement found in the natural photosystem, the principle is the same. The system contains five macromolecules in the shape of a honeycomb that can capture light to create a sheath around each reactor core. Moreover, such small power stations are efficient and successful at harvesting sun energy and wavelengths from the green portion of the color spectrum can also be used. According to the researchers, the results aid in enhancing the efficiency of solar technology. The research was published in the journal Nature Chemistry on December 3, 2018.

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