Spanish researchers design all-in-one down-conversion chemistry for white LEDs

October 15, 2018 // By Julien Happich
Using elaborate chemical synthesis techniques, a team of Spanish researchers led by Rubén Costa of IMDEA Materials (Madrid) was able to synthetize all three Red Green Blue (RGB) colour down-converters typically used for the manufacture of white LEDs into one down-converter chemistry covalently and stably bonded within a silica framework.

All organic white LEDs typically require a precise layered approach with several organic semiconductors and injection, charge transport/blocking, and light emission layers, while inorganic solutions call for the use of colour down-converting coatings made of rare-earth materials on top of a UV or blue-emitting chip. Even when thoroughly mixed at the right ratio to emit a sun-like spectrum, the discrete chemistries used in organic white LEDs show discrepancies in stability, affecting a white LED's useful lifetime. The use of rare-earth materials for the inorganic alternative implies higher production costs and uncertain availability. Colour tuneability through chemistry also remains a challenge.

In a paper titled "White-emitting organometallo-silica nanoparticles for sun-like light emitting diodes" published in Materials Horizons, the researchers took a more direct approach to down-conversion, by synthesizing luminescent organometallo-silica nanoparticles bearing a mix of blue-, green-, and red-emitting organometallic Ir(III) complexes simultaneously encapsulated via sol-gel coordination chemistry inside the silica nanoparticles. The sol-gel coordination process allowed the researchers to kinetically control the covalent bonding of the three organometallic chromophores at the molecular level, prior to the formation of the silica matrix around them.


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