Ag-incorporated Alq3 nanowires: Promising material for organic luminescent devices

Nanowires of pure Alq3 and Ag incorporated Alq3 have been fabricated using thermal vapor transport method. Scanning electron micrographs of these nanowires suggest that these nanowires have the diameters ranging from 60 nm to 100 nm and lengths of several microns. X-ray Diffraction (XRD) analysis predicts the poly-crystalline nature of these as-prepared Alq3 and Ag incorporated Alq3 nanowires. Energy Dispersive X-ray (EDX) analysis confirms the presence of Ag in the nanowires synthesized using Ag incorporated Alq3 powders. UV-visible spectroscopic analysis suggests that Ag is present in these nanowires in the form of small clusters (oligomers) incorporated within the Alq3 matrix. The effect of Ag incorporation on the vibrational states of Alq3 molecules has been studied using FTIR spectroscopy. The photoluminescence (PL) emission spectra of Ag incorporated Alq3 nanowires show a single broad band centered around 505 nm, which is similar to that of the pure one, but PL intensity is enhanced with Ag concentration. The Ag incorporated Alq3 nanowires with concentration ratio of Alq3:Ag=1:0.7 have been found to have the highest PL intensity, which is around 4 times stronger than that of pure Alq3 nanowires. The enhancement in PL intensity is attributed to the local field enhancement around Alq3 molecules, and moderate structural modifications, due to Ag incorporation. Photoluminescence quenching has been observed for the samples having Ag concentration higher than that in the sample having the ratio Alq3:Ag = 1:0.7. This quenching is attributed to the non-radiative energy transfer between Alq3 molecules and Ag oligomers. These results suggest that Ag incorporated Alq3 nanowires may be useful for the development of next generation organic optoelectronic devices.