Comprehensive study on photophysical properties of Eu(TTA)3bipy phosphor molecularly doped in PMMA and PS matrices

Abstract

Successful synthesis of the most studied europium activated β-diketonate red light emitting complex Eu(TTA)3bipy in which 2,2′ bipyridine is used as a synergistic ligand has been demonstrated. This complex is incorporated into Polymethylmetha acrylate (PMMA) and Polysterene (PS) at 10 and 25 wt% to check its compatibility with polymers. The photophysical properties of molecularly doped blended thin films were characterized by UV–visible absorption spectra and photoluminescence (PL) spectra in the solid state as well as by dissolving them in different organic solvents such as chloroform, tetrahydrofuran (THF), toluene (basic) and acetic acid (acidic). From the results of UV–vis absorption spectra, probability transition parameters were calculated. Thin films illustrated red emission, always peaking at 614 nm when excited at 380 nm, irrespective of solid state or solvated state. Comparison of optical intensities of the doped thin films dissolved in chloroform for different wt % and the pure complex in the same solvent reveals enhancement in PL intensity in the doped thin films rather than in pure complex. Relative intensity ratio (R-values) for different wt% of doping in PMMA and PS matrix were found to be in the range of 13.0–14.3. CIE coordinates of Eu (TTA)3bipy in PMMA and PS for 10 and 25 wt% in solid state were found to be (0.66, 0.34) and (0.66, 0.33), whereas in solvated state the same was found to be (0.67, 0.32) and (0.66, 0.34), respectively, clearly indicating unique emission wavelength. These results dictates that the blended films are more economical as compared to the pure Eu(TTA)3bipy, proving its great potential as strong red light emitting phosphor for the fabrication of optoelectronic devices such as OLEDs, flat panel displays by solution processing techniques. Keywords: Synergistic ligand, PMMA, PS, Probability transition parameters, OLEDs, Solution processing techniques