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Research

Cable Supercapacitors

Currently, millions of miles of electrical cables have been used for providing electrical connections in machineries, equipment, buildings and other establishments. Energy storage devices are completely separated from these electrical cables if used. However, it will revolutionize energy storage applications if both electrical conduction and energy storage can be integrated into the same cable. Here, a dual-function coaxial supercapacitor cable (CSC), which has the capability to be used as an electrical cable and an energy storage device, is demonstrated. Similar to typical coaxial cables, the inner core is used for electrical conduction and the overlying layer is used for energy storage. The integrated CSC device shows excellent flexibility and bendability, long and stable cycle lifetimes, and high energy and power densities. All these remarkable results demonstrate a clear technological advance achieved by clubbing electrical conduction and energy storage into one cable.

For details: “Highly Ordered MnO2 Nanopillars for Enhanced Supercapacitor Performance” Adv. Mater. 26, 4279-4285 (2014). (Highlighted by Nature in News & Views).

Plasmonic Structures

We have developed a facile fabrication technique for producing tunable plasmonic substrates. With this technique, we are able to tune the plasmon resonance of the substrate to match the molecular resonance of an organic dye with a simple additional fabrication step. Two oscillators can exchange their energies and become coupled when placed in the vicinity of each other. Our nanohole structures are very promising candidate for photon-exciton coupling. This is because nanoscale light confinement is possible with their plasmon resonances. Moreover, since our structures are open cavities, accessing the mode volume in which the coupling take place is relatively easy. This allows us to probe physical/chemical properties of the coupled states. We have found that when we match the plasmon resonance of the nanohole structure to an organic dye such as R6G, Raman scattering signal from the sample is significantly enhanced. Our ongoing research is to explore the use of our fabrication technique to fabricate plasmonic structures with unique properties.

For details:

  • Li, J., Madiyar, F., Ghate, S., Kumar, K.S. and Thomas, J., 2023. Plasmonic organic electrochemical transistors for enhanced sensing. Nano Research, 16(2), pp.3201-3206.
  • Chantharasupawong, P.; Tetard, L.; Thomas, J., Coupling Enhancement and Giant Rabi-Splitting in Large Arrays of Tunable Plexcitonic Substrates. The Journal of Physical Chemistry C 2014, 118, 23954-23962.

Wearable Energy Storage and Harvesting Ribbons (2016)

Wearable technology has been in the limelight ever since the electronics started becoming smaller and smaller. The miniaturization of gadgets became even easier with the introduction of nanoscience and technology. We have fabricated a flexible and wearable integrated device in the form of thin ribbons which can simultaneously harvest and store energy. An array of such devices are woven into a textile form that can be knitted on clothes. The integrated device consists of a perovskite solar cell on a copper ribbon to harvest the light energy and a thin film supercapacitor on the other side of the ribbon is used to store the charges generated.

Superstructures for Photodetectors and Synapses

The human brain has the power to process and memorize information simultaneously. Neuromorphic computing is designed based on this principle. We recently developed optoelectronic synapsis using a superstructure, which is a baby step in this direction. This superstructure is developed by growing highly photosensitive methylammonium lead bromide perovskite quantum dots (PQDs) on graphene, by a defect-mediated process. Graphene, a two-dimensional sheet of carbon atoms, is a dream material for electronic and optoelectronic applications due to its interesting properties such as broad bandwidths, very high electron mobility and high transparency besides outstanding flexibility and stability. However, a major disadvantage of graphene is the low charge generation efficiency, with only 2.3% of incident light being converted to electric charge. This low charge generation limits its applications in optoelectronic and photonic devices. Contrarily, PQDs have emerged as attractive materials for optoelectronic devices due to their high extinction coefficients, bandgap tunability, high photoluminescence quantum yield, and narrow emission spectrum. However, the charge transport properties of these PQDs are inferior when compared to graphene. By combining these two materials in a superstructure enabled us to achieve high optical absorption and charge transport in an extremely thin medium. The neuromorphic computing ability of our device was tested via face recognition experiments.

Publications:

  • Thomas, J., Roy, T., Das, S., Pradhan, B. and Li, J., University of Central Florida Research Foundation Inc UCFRF, 2023. Photonic synapse based on graphene-perovskite quantum dot for neuromorphic computing. U.S. Patent 11,574,177.
  • J. Li, P. Dwivedi, K. S. Kumar, T. Roy, K. E. Crawford, J. Thomas, Growing Perovskite Quantum Dots on Carbon Nanotubes for Neuromorphic Optoelectronic Computing. Adv. Electron. Mater. 2021, 7, 2000535. https://doi.org/10.1002/aelm.202000535
  • Pradhan, B., Das, S., Li, J., Chowdhury, F., Cherusseri, J., Pandey, D., … & Thomas, J. (2020). Ultrasensitive and ultrathin phototransistors and photonic synapses using perovskite quantum dots grown from graphene lattice. Science advances, 6(7), eaay5225 (2020). DOI:10.1126/sciadv.aay5225