Transparent electrodes from the tree

In the future, blades will provide better and cheaper solar cells, LEDs or displays. Researchers are transforming the leaf veins into electrodes with excellent optical and electronic properties.

Scientists, engineers and architects have always been drawn to nature. As early as 1505 Leonardo da Vinci analysed the flight of birds and tried to transfer his findings to flying machines. But it was only in the last few decades that bionics was able to establish itself as a scientific discipline.

Recently, “nature observers” at Leibniz-IPHT have been inspired by the perfectly sophisticated plant organism and developed electrodes with a high power density and low material consumption from leaf veins.

Electrodes from the magnolia tree

Like photochemical factories, plant leaves convert water and CO2 into carbohydrates and oxygen by photosynthesis. A network of leaf veins supplies the leaf cells with water and nutrients and transports the carbohydrates produced by photosynthesis to other parts of the plant.

IPHT researchers are now using this efficient transport network to transport electricity. They detached the chlorophyll from the leaves of the purple magnolia (Magnolia liliiflora), metallized the veins with copper and allowed electric current to flow through them. In this way, the leaf skeletons became transparent, conductive electrodes, because the network of veins still lets light through.

And at the same time they “survive” current densities of up to 6,000 amperes per square centimeter. The leaf electrodes also proved superior in terms of optical transmission in the UV and infrared range.

The advantages of the “bio-solution” are obvious: Electrodes made from leafy leaves require much less material, because the copper consumption for metallization is very low. And due to the superior, vein-like structures of broadleafs, the silver consumption for the mass production of solar cells would also be reduced to less than a tenth of the current level. In addition, the electrically conductive and optically transparent “leaf vein electrodes” open up new possibilities for the construction of batteries and supercondesators as well as for the design of novel LEDs or displays.