Investigations on optical properties of Eu0.5Sm0.5(TTA)3tppo hybrid organic complexes molecularly doped in PMMA and PS matrices

An attempt has been made to synthesize orange-red light-emitting rare earth-doped polymer matrices Eu0.5 Sm0.5 (TTA)3 tppo (Eu = europium, Sm = samarium, TTA = thenoyltrifluoroacetone, tppo = triphenylphosphine oxide) hybrid organic complex by solution technique. Blended thin films were made by molecularly doping the complex in polymethylmethacrylate (PMMA) and polystyrene (PS) polymers at different weight percentages (5%, 10%). These films were solvated in basic and acidic media to explore the effect of solvent on its luminescence properties. UV-visible absorption spectra of these solvated films portray two peaks corresponding to π→π* and n→π* optical transitions in the range 240-275 nm and 370-390 nm in basic medium. Energy band gap of these thin films in basic medium was found between 3.16 eV to 3.20 eV and 3.12 eV to 3.22 eV in acidic medium. Photoluminescence spectra of all films in dichloromethane showed an intense peak at 614 nm, whereas in formic acid, the same were found at 475 nm, which fell in the orange-red and blue region of the visible spectrum, respectively. CIE coordinates of these solvated films in various solvents and at different weight percentages revealed tunable orange-red to blue light emission with change in polarity of the solvent. Therefore the synthesized complexes blended in the polymers can be shaped into flexible films for fabrication of organic light-emitting diodes (OLEDs) with consistent results, proving their prospect as colour tunable light emissive materials for OLED devices, lasers, displays, and solid-state lighting.