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Covalent Organic Framework derived flexible white-light emitters  Nov 14, 2018

A hexagonal honey-comb structured COF built from green and yellow emitting monomers giving rise to a solvent dependent chromism. This COF has emits flexible white-light when dispersed in a solution-processible polymer in very low concentrations. (Image Credit: Dr. R. Vaidhyanathan)

In a collaborative effort from research groups at IISER Pune (R. Vaidhyanathan, Partha Hazra) and IIT Bombay (Dinesh Kabra), a covalent organic framework (COF) material has been synthesized, which can be used for the coating of white-Compact Fluorescent Lamps (CFLs) as an alternative for commercially used metallic white-phosphors.

Depending on the concentration of this COF (powder) in a polymer matrix, the color temperature can be tuned from cool to natural white which is essential for making the CFL lamp of desirable brightness (cool: bluish white; hot: reddish white). The use of this all-organic material for the conversion of higher energy UV light into lower energy visible light brings environmental friendliness. The team has also addressed the issue of durability of this COF as a white-fluorophore under harsh (acidic/basic) and humid environments. Loading a small amount (0.3 wt %) of this COF in a polymer matrix is sufficient for bright white lighting, which could make it cost-effective.

“Metal-based phosphors can be expensive, toxic and pose difficulty in disposal. Our findings can contribute to a suitable alternative for cost-effective and environmentally benign solid-state lighting/displays. Further work is required to improve the life-time of these white emissions to make it comparable to the metal-based phosphors,” says Dr. Vaidhyanathan.

This research published in the Journal of American Chemical Society (140(41):13367–13374) is titled “Anthracene-Resorcinol derived covalent organic framework as flexible white light emitter” and is authored by Sattwick Haldar, Debanjan Chakraborty, Bibhisan Roy, Gangadhar Banappanavar, Kushwaha Rinku, Dinesh Mullangi, Partha Hazra, Dinesh Kabra, and Ramanathan Vaidhyanathan.

This work received funding from DST-Nanomission, SERB, DST-INSPIRE, and the MHRD-FAST program.

- with inputs from Dr. R. Vaidhyanathan