Soft X-ray excited optical luminescence from functional organic materials

This brief report reviews some of the recent findings in the study of synchrotron based X-ray excited optical luminescence (XEOL) from representative organic light emitting device (OLED) and related functional organic materials. The systems of interest include Alq3, aluminium tris(8-hydroxylquinoline); Ru(bipy)32+, tris-(2,2-bipyridine) ruthenium(II); Ir(bpy)3, tris(2-phenyl-bipyridine)iridium; PVK (poly(N-vinylcarbazole)) and [Au2(dppe)(bipy)]2+, a Au(I) polymer containing 1,2-bis(diphenylphosphino)ethane and the 4,40-bipyridyl ligands, as well as TBPe (2,5,8,11-tetra-tert-butylperylene) polyhedral crystals and fluorescein isothiocyanate (FITC) and FITC-labelled proteins. It is shown that tunable and pulsed X-rays from synchrotron light sources enable the detailed tracking of the optical properties of organic functional materials by monitoring the luminescence in both the energy and time domain as the excitation energy is scanned across an element-specific absorption edge. The use of XEOL and X-ray absorption spectroscopy (XAS) in materials analysis is illustrated.