Flexible transparent displays based on core/shell upconversion nanophosphor-incorporated polymer waveguides (original) (raw)
Related papers
Composites Part B: Engineering, 2015
The work was to investigate the possibility of making polymer-inorganic nano-composite films with upconversion fluorescence properties using the double beam matrix-assisted pulsed laser evaporation (DB-MAPLE) method. The existing pulsed laser deposition vacuum chamber was modified to accommodate two laser beams of different wavelengths for simultaneous ablation of two separate targets: a polymer host and a rare earth containing rare earth ion enriched upconversion fluoride dopant. The polymer target was prepared in chlorobenzene and kept frozen during the ablation with circulating liquid nitrogen in accordance with the MAPLE procedure. It was ablated with 1064 nm beam from a pulsed Nd:YAG laser. The pellets made of the synthesized powders of inorganic phosphors of NaYF 4 :Yb 3+ , Er 3+ and NaYF 4 :Yb 3+ , Ho 3+ were ablated with 532-nm beam from the same laser. The plumes from both targets were kept overlapping on the substrate during the deposition. X-ray diffraction analysis revealed that the most favorable for upconversion emission of the inorganic target materials was the hexagonal, beta phase of the NaYF 4 matrix existing at a baking temperature between 400 and 600°C. The fabricated nanocomposite films were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and optical fluorescence spectroscopy. The polymer nano-composite films generally retained the crystalline structure and the upconversion fluorescence properties of the initial rare earth compounds due to better control of the deposition process of the materials with substantially different properties. The proposed method can be potentially used for making a wide variety of nano-composite films.
New luminescent polymers for LEDs
Synthetic Metals, 1997
Recent results are reported on the synthesis of statistical copolymers 8 and 9 derived from the highly luminescent silyl PPV derivative (DMOS-PPV) with various alternative building blocks carrying side chains capable of supporting polyelectrolytes. These polymers are prepared by Gilch dehydrohalogenation polymerization. It is of interest to study the effect on charge transport in standard electroluminescent (EL) devices using these PPV copolymers. Moderately efficient conventional single-layer devices are obtained for copolymer 9. When fabricated in a light-emitting electrochemical cell (LEC) configuration (lithium triflate) without any extra supporting polymer electrolyte (e.g., poly(ethylene oxide), PEO), devices based on both 8 and 9 show lower turn-on voltages and improved efficiency.
Fabrication of novel light-emitting devices based on green-phosphor/conductive-polymer composites
Philosophical Magazine Letters, 2007
We report on light-emitting devices based on a green-phosphor compound (Mn-doped zinc silicate, Zn 2 SiO 4 :Mn) dispersed in a conductive polymeric blend (poly-o-methoxyaniline/polyvinylene fluoride, POMA/PVDF-TrFE). The devices exhibited high luminance in the green, good stability and homogeneous brilliance over effective areas up to 5 cm 2 . The electroluminescence (EL) spectrum presented essentially the same characteristics as the photoluminescence (PL) and cathodoluminescence spectra, indicating that the light emission originates from decay of the same excited species, regardless of the excitation source. Operating characteristics were analyzed with current density-voltage (J-V ) and luminancevoltage (L-V ) curves to investigate the nature of the electroluminescence of the active material, which is still not completely understood.
Highly Versatile Upconverting Oxyfluoride-Based Nanophosphor Films
ACS Applied Materials & Interfaces, 2021
Fluoride-based compounds doped with rare-earth cations are the preferred choice of materials to achieve efficient upconversion, of interest for a plethora of applications ranging from bioimaging to energy harvesting. Herein, we demonstrate a simple route to fabricate bright upconverting films that are transparent, self-standing, flexible, and emit different colors. Starting from the solvothermal synthesis of uniform and colloidally stable yttrium fluoride nanoparticles doped with Yb3+ and Er3+, Ho3+, or Tm3+, we find the experimental conditions to process the nanophosphors as optical quality films of controlled thickness between few hundreds of nanometers and several micrometers. A thorough analysis of both structural and photophysical properties of films annealed at different temperatures reveals a tradeoff between the oxidation of the matrix, which transitions through an oxyfluoride crystal phase, and the efficiency of the upconversion photoluminescence process. It represents a si...
Dyes and Pigments, 2019
Several novel orange emission supramolecular phosphorescent polymers (SPPs) with different counterions of PF 6 − , Br − and BIm 4 have been developed for polymer light-emitting diodes. The formation of SPPs, utilizing efficient non-bonding assembly of dibenzo-24-crown-8-tethered iridium complex and dibenzylammoniumfunctionalized fluorene-dibenzothiophene-S,S-dioxide cooligomer, are monitored by 1 H NMR and viscosity measurement. The influences of different counterions on the optical, thermal and electroluminescent (EL) properties of the resulting SPPs, as well as the supramolecular assembly behavior are investigated in detail. These SPPs display high glass transition temperatures of ca. 100°C. The single-emissive-layer PLED with SPP-PF 6 exhibits the highest device efficiency of 12.32 cd A −1 with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.57, 0.43). More importantly, owing to "spacer" effect of the large BIm 4 counterion, the device based on SPP-BIm 4 show very low efficiency roll-off.
Electrical and luminescent properties of double-layer oligomeric/ polymeric light-emitting diodes
Synthetic Metals, 1996
We report the use of α-sexithiophene (T6) thin films sublimed onto glass substrates coated with indium-tin oxide in light-emitting diodes. Absolute photoluminescence quantum efficiencies were found to be in the range 10−2–10−3%, and indicate that T6 should be used as a hole injector into an emissive layer, rather than as a luminescent layer. We have fabricated double-layer organic light-emitting diodes where a cyano-substituted derivative of poly(p-phenylenevinylene) (PPV), MEH-CN-PPV, was spun on top of the T6 layer prior to evaporation of Ca-Al cathodes. Turn-on voltages for electroluminescence of about 3 V were found in structures with total thickness between 160 and 230 nm, while internal quantum efficiencies were up to 0.4%, i.e. at least ten times less than those measured in comparative devices where a PPV hole-injecting layer was used in place of T6. The substantial difference is interpreted on the basis of a significant lowering of the barrier to electron ejection from the luminescent layer into the hole-injecting layer when passing from PPV to T6. This allows inefficient recombination to take place in T6, as confirmed by the electroluminescence spectra.
Solution Processable Phosphorescent Red Luminescent Polymer for OLED Devices
The Journal of The Institute of Image Information and Television Engineers, 2012
Organic light-emitting diodes (OLEDs) are being considered as the next generation technology of flat-panel display. The development of red phosphorescent Ir(III) complexes with high quantum yields compared to green emitters has been found to be relatively challenging because they are intrinsically less emissive. Although Ir(piq) 3 1) and
The Journal of Physical Chemistry C, 2017
In this work, we report a phenomenon that upconversion emission intensity of Er 3+ was enhanced by cadmium. Cd 2+ was taken with 0, 3, 10, 20, 30 and 40 mol% as a new dopant to codope LiY 0.78 Yb 0.20 Er 0.02 F , meanwhile the doping effects on the crystal structure, morphology and the upconversion fluorescence emission are investigated by XRD, Rietveld refinement, TEM, upconversion spectroscopy analysis methods in detail. The green upconversion emission intensity was enhanced and the maximum emission intensities were enhanced to twice when 10 mol% Cd 2+ was codoped into tetragonal LiYF 4 , while its decay lifetime was reduced. Additionally, we further designed the synthesis of the homogeneous LiYF 4 :20%Yb,2%Er,10%Cd@LiYF 4 of which the emission intensity is 11 times higher than the Cd 2+-free nanocrystals, meanwhile an intriguing morphology of core-shell nanocrystals was obtained. This investigation may be useful for design and improvement of upconversion materials for fulfilling the prerequisite of the practical application.
Synthetic Metals, 2016
The emission color of a single-layer polymer light-emitting diode (PLED) was tuned using an external layer. We combine an electroluminescent polymer, known as poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT), embedded in a diode-like structure (ITO/PEDOT-PPS/F8BT/Ca/ Al), and a film of poly(vinyl alcohol) (PVA) containing one of the xanthene dyes, either Erythrosin B (ERB) or Rose Bengal (RB), used as an external photoluminescent layer. The emission color is tuned from the CIE coordinates (0.34, 0.64) for the bare F8BT-diode to (0.39, 0.57) using a 42mmPVA:RBfilmandto(0.35,0.61)usinga42 mm PVA:RB film and to (0.35, 0.61) using a 42mmPVA:RBfilmandto(0.35,0.61)usinga55 mm PVA:ERB film. It was obtained based on trivial photophysical processes: xanthene dyes partially absorb the electroluminescence (EL) emissions coming from the F8BT-diode, decaying radiatively and emitting light by photoluminescence (PL). This method is versatile and may be extended to other combinations of EL and PL materials, tuning the color output and giving different CIE color coordinates. Because both the EL and PL layers are polymer-based systems, they can be used in the development of flexible displays and illumination sources. Furthermore, the PL layer is a self-supported film formed by water-soluble materials, with the advantage of being environmentally friendly, commercially available and low-cost. The PLED delivered a brightness of 123 cd/m 2 at 9 V. 2016 Elsevier B.V. All rights reserved.