White-Light Emitting Di-Ureasil Hybrids

Abstract

White-light emitting materials have emerged as important components for solid state lighting devices with high potential for the replacement of conventional light sources. Herein, amine-functionalized organic-inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains codoped with lanthanide-based complexes, with Eu3+ and Tb3+ ions and 4,4′-oxybis(benzoic acid) and 1,10-phenanthroline ligands, and the coumarin 1 dye were synthesized by in situ sol–gel method. The resulting luminescent di-ureasils show red, green, and blue colors originated from the Eu3+, Tb3+, and C1 emissions, respectively. The emission colors can be modulated either by variation of the relative concentration between the emitting centers or by changing the excitation wavelength. White light emission is achieved under UV excitation with absolute quantum yields of 0.148 ± 0.015, 0.167 ± 0.017, and 0.202 ± 0.020 at 350, 332, and 305 nm excitation, respectively. The emission mechanism was investigated by photoluminescence and UV–visible absorption spectroscopy, revealing an efficient energy transfer from the organic ligands to the Ln3+ ions and the organic dye, whereas negligible interaction between the dopants is discerned. The obtained luminescent di-ureasils have potential for optoelectronic applications, such as in white-light emitting diodes.

A Hybrid Materials Approach for Fabricating Efficient WLEDs Based on Di‐Ureasils Doped with Carbon Dots and a Europium Complex

“…[ 74 ] The values found were 30.4, 27.6, and 27.6 (±0.1) Å for dU6‐aCDs, dU6‐Eu, and dU6‐aCDs/Eu, respectively, in agreement with the values previously reported for the non‐doped d‐U(600) matrix. [ 21,34 ]…”

“…[74] The values found were 30.4, 27.6, and 27.6 (±0.1) Å for dU6-aCDs, dU6-Eu, and dU6-aCDs/Eu, respectively, in agreement with the values previously reported for the non-doped d-U(600) matrix. [21,34] The FT-IR spectra of d-U(600), dU6-aCDs, dU6-Eu, and dU6-aCDs/Eu (Figure S7a, Supporting Information) show broad bands centered at ~3540 and ~3340 cm -1 , assigned to N-H and O-H stretching vibration modes, respectively. The band due to the stretching vibration of the isocyanate (-N=C=O) moiety of the 3-isocyanateproplytriethoxysilane (ICPTES) precursor compound, expected at 2272 cm -1 , is absent in all the spectra, confirming the completion of the reaction between the -N=C=O group of ICPTES and the terminal amino (NH2) groups of the precursor ED-600 diamine.…”

“…[11] Presently, other requirements involving flexibility, transparency, and large-scale fabrication have also been extensively considered in white-light-emitting film fabrication, facing the new challenges of the domain of flexible and light-weight electronic devices. [13,14,21] To produce flexible white-light-emitting films for WLEDs, the incorporation of chromophores into organic-inorganic hybrid structures synthesized by the sol-gel method has emerged as an attractive solution to design low-cost new phosphors through an energy-saving and large-scale fabrication process. [14,22,23] In fact, the di-and tri-urea cross-linked poly(oxyethylene) (POE)/siloxane hosts (di-ureasils [24] and triureasils [25] , respectively) demonstrated a low absorbance in the UV range (<1 dB cm −1 ) [26] and an excellent dispersion ability that prevents the interaction of Ln 3+ complexes with OH oscillators, reducing nonradiative deactivations [27] and allowing the production of fine-tunable emission colors from red-to-yellowto-green.…”

“…[14,22,23] In fact, the di-and tri-urea cross-linked poly(oxyethylene) (POE)/siloxane hosts (di-ureasils [24] and triureasils [25] , respectively) demonstrated a low absorbance in the UV range (<1 dB cm −1 ) [26] and an excellent dispersion ability that prevents the interaction of Ln 3+ complexes with OH oscillators, reducing nonradiative deactivations [27] and allowing the production of fine-tunable emission colors from red-to-yellowto-green. [13,[28][29][30][31][32][33] In all the examples found, the blue component that yields white-light is provided by the intrinsic blue emission of the host [34] or from the addition of commercial dyes [21] or polymers. [29] The relatively low emission quantum yield of the ureasil emission (<0.2), [35] the difficulty to tune the emission of the dyes or polymers, and the poor photostability of their emission are important constraints motivating the search of efficient blue-emitting materials.…”

“…[ 11 ] Presently, other requirements involving flexibility, transparency, and large‐scale fabrication have also been extensively considered in white‐light‐emitting film fabrication, facing the new challenges of the domain of flexible and light‐weight electronic devices. [ 13,14,21 ]…”