Dr. Rekha Sharma

Dr. Rekha Sharma

Research Area A

Cluster of Excellence livMatS @ FIT – Freiburg Center for Interactive Materials and Bioinspired Technologies


Correlating redox properties of organic materials with triboelectric charge-separation – from basic understanding to novel materials for efficient triboelectric energy harvesting

Project description
Charge separation at interfaces is the mechanism underlying the triboelectric effect. This can be exploited to harvest mechanical energy from the surroundings in functional materials systems. In this project novel organic materials will be developed to make triboelectric charge separation more efficient and with the ultimate goal to increase the performance of triboelectric nanogenerators used for energy harvesting. This will be preceded by a fundamental study on the effect of the redox activity of organic moieties on triboelectric charge separation by atomic force microscopic studies. Theoretical investigations will provide insight into the physical origins of the charge separation. The results of these fundamental studies will allow selecting the best organic moieties for incorporation into materials (i.e polymers), which will then be synthesized and used in macroscopic devices to investigate triboelectric charge separation at their interfaces.

Project outcomes
In this project, I have synthesized novel organic materials like thiol functionalized donors - triphenyl amine, Carbazole, Phenothiazine, Tetrathiafulvalene and acceptors like 1,8-Naphthalimide to make triboelectric charge separation more efficient. The effect of the redox activity of organic compounds on efficient charge separation is investigated by contacting experiments with AFM-based Force Spectroscopy and Kelvin Probe Force Microscopy (KPFM) using small redox-active molecules covalently attached to the AFM cantilever tip and substrate followed by detection of surface potentials before and after contact.
KPFM proves charge transfer between donor and acceptor molecules, which makes redox-active molecules promising for the application in triboelectric nanogenerators.

Prof. Dr. Birgit Esser