Question

effect of electron withdrawing group/ electron donating group on emission colour of the Alq3

Answer 1

           The central atom in the complex is Aluminum, surrounded by three bidentate ligands (8-hydroxyquinoline). It is the main component of organic light emitting diodes (OLEDs). The luminescence properties can be varied by varying the substituents on quinoline rings.

As per the literature, Alq3 sample exhibit emission peak at 500 nm. When Alq3 was substituted with electron donating groups like -CH3 or extended conjugation groups at 5th position creates red shift of ~ 50nm (shift to longer wavelengths). The shift was due to the decrease in the band gap of the material. Similarly, when Alq3 was substituted with electron withdrawing groups like -Cl at 5th position creates a small red shift of ~ 30nm.

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