\n<\/p>\n
All reagents and solvents used for the synthesis of the compounds were purchased from Aldrich and Acros companies and used without further purification. 1H nuclear magnetic resonance (NMR) spectra were recorded using a Varian Mercury plus 400NB spectrometer, with tetramethylsilane (TMS) as the internal standard. Molecular masses were determined using a FINNIGAN LCQ electrospray ionization mass spectrometer or a matrix-assisted laser desorption\/ionization time-of-flight mass spectrometer. Elemental analyses were performed using a Vario EL III elemental analyser. Suitable single crystals for X-ray diffraction analysis were obtained by slowly diffusing 12\u2009ml of n-hexane into a 3-ml dichloromethane solution of ArPPOA (10\u2009mg) at room temperature. X-ray diffraction data were collected at 295\u2009K on a Rigaku Xcalibur E diffractometer with graphite-monochromatized Mo\u2009K\u03b1 radiation (\u03bb\u2009=\u20090.71073\u2009\u00c5) in \u03c9 scan mode. The structures were solved using direct methods and difference Fourier syntheses. Non-hydrogen atoms were refined by full-matrix least-squares techniques on F2 with anisotropic thermal parameters. Hydrogen atoms attached to carbons were placed at calculated positions (C\u2013H\u2009=\u20090.93\u2009\u00c5) with U(H)\u2009=\u20091.2Ueq(C), following the riding model approximation. All calculations were carried out using the SHELXL97 program.<\/p>\n
We performed transmission electron microscopy measurements using a field-emission transmission electron microscope (JEOL JEM-2010F) operated at an acceleration voltage of 200\u2009kV. Absorption and PL emission spectra were measured using a Shimadzu UV-3150 spectrophotometer and a Shimadzu RF-5301PC spectrophotometer, respectively. Cyclic voltammetry was conducted using an Eco Chemie B.V. Autolab potentiostat in a three-electrode cell with a glassy carbon working electrode, a platinum wire counter electrode and a silver\/silver chloride (Ag\/AgCl) reference electrode. Electrochemical experiments were carried out under a nitrogen atmosphere at room temperature in dichloromethane. Phosphorescence spectra were measured using an Edinburgh FLS1000 fluorescence spectrophotometer at 50\u2009K.<\/p>\n
Time decay spectra were measured using the time-correlated single photon counting method with a picosecond hydrogen lamp for the 100\u2009ps to 10\u2009\u03bcs range and a microsecond pulsed xenon light source for 1\u2009\u03bcs to 10\u2009s lifetime measurements. The synchronization photomultiplier collected the signal and the multi-channel scaling mode of the PCS900 fast counter PC plug-in card was used for data processing. Prompt and delayed fluorescence lifetimes were respectively measured with nanosecond and microsecond time decay methods. Lifetime values were simulated using an exponential fitting function in Fluoracle software.<\/p>\n
Nanocrystal-based films (20\u201340\u2009nm) for optical analysis were prepared through spin coating. The PLQYs of these films were measured using a Labsphere 1-M-2 integrating sphere (\u03d5\u2009=\u20096\u201d) coated by BenFlect, providing efficient light reflection across a wide range of 200\u20131,600\u2009nm. The integrating sphere was coupled with the FLS1000 system. The absolute PLQY was determined by recording two spectral (emission) scans. The first spectrum captured both the scattered light and the emission from the sample, whereas the second spectrum measured the scattered light from the BenFlect coating. By integrating and subtracting the scattered light parts from both spectra, we determined the photon number absorbed by the sample (Na). The emission of the sample was integrated to calculate the emissive photon number (Ne). The absolute PLQY (\u03b7) was then calculated using the equation \u03b7\u2009=\u2009Ne\/Na. Spectral correction (emission arm) was applied to the raw data after background subtraction and the quantum yield was calculated from the spectrally corrected curves using the F900 software wizard.<\/p>\n
NaGd1-xF4:Tb\/Eux@OA nanocrystals: Lanthanide nanocrystals were synthesized according to a well-documented coprecipitation method30. In a typical experiment for synthesizing NaGd1-xF4:Tbx nanocrystals, GdCl3\u00b76H2O (1-x\u2009mmol) and TbCl3\u00b76H2O or EuCl3\u00b76H2O (x\u2009mmol) were mixed with OA (6\u2009ml) and 1-octadecene (15\u2009ml) in a 100-ml flask. The mixture was heated to 140\u2009\u00b0C for 3\u2009h. After cooling to 50\u2009\u00b0C, a methanol solution (10\u2009ml) containing NaOH (0.1\u2009g, 2.5\u2009mmol) and NH4F (0.148\u2009g, 4\u2009mmol) was added and the mixed solution was stirred for 12\u2009h. The temperature was then raised to 70\u2009\u00b0C to remove methanol. After that, the solution was heated to 240\u2009\u00b0C under an argon atmosphere for 45\u2009min, followed by cooling to room temperature. The resulting nanocrystals were extracted by repeated precipitation with a mixture of ethanol and hexane, collected by centrifugation at 12,000\u2009rpm for 5\u2009min and redispersed in 9\u2009ml of hexane.<\/p>\n
The synthesis followed the same procedure as above, with the inclusion of EuCl3\u00b76H2O (x\u2009mmol, x\u2009=\u20090.01, 0.05, 0.08 or 0.10).<\/p>\n
In a typical process32, 1\u2009ml of the as-prepared OA-capped nanocrystals dispersion in hexane (about 50\u2009mg\u2009ml\u22121) was combined with 1\u2009ml of a N,N-dimethylformamide (DMF) solution containing NOBF4 (0.011\u2009g, 0.1\u2009mmol) at room temperature. The mixture was ultrasonicated for 20\u2009min to remove oleate ligands on the surface, followed by the addition of 1\u2009ml of toluene and further sonication for another 20\u2009min. The ligand-free nanocrystals were collected by centrifugation and redispersed in DMF (1\u2009ml). For purification, 1\u2009ml of a hexane\u2013toluene solution (1:1\u2009v\/v) was added to flocculate the dispersion and the precipitate was collected by means of centrifugation. The nanocrystals were then redispersed in 2\u2009ml of EtOH to form a stable colloidal dispersion.<\/p>\n
For ligand modification, sodium hydroxide (0.002\u2009g, 0.05\u2009mmol) in 1\u2009ml of ethanol was added to the desired ligand (0.05\u2009mmol) in 2\u2009ml of ethanol to prepare a ligand salt solution. This solution was added to an ethanol dispersion of ligand-free nanocrystals (0.001\u2009mmol) and ultrasonicated for two hours to ensure ligand coordination to nanocrystal surfaces. Excess ligand was removed by centrifugation and the modified nanocrystals were redispersed in ethanol for optical measurements or in DMF for device fabrication.<\/p>\n
Under an argon atmosphere, 1-bromo-2-methylbenzene (1.186\u2009ml, 10\u2009mmol) in 10\u2009ml of dry ether was added dropwise to a mixture of magnesium turnings (0.267\u2009g, 11\u2009mmol) and a small piece of iodine in 10\u2009ml of dry ether at room temperature. The reaction was stirred at 40\u2009\u00b0C for one hour. After cooling to 0\u2009\u00b0C, chlorodiphenylphosphine (1.980\u2009ml, 11\u2009mmol) in 10\u2009ml of dry ether was added dropwise and stirred for 12\u2009h. The reaction was quenched by adding water and the mixture was extracted with CH2Cl2 (3\u2009\u00d7\u200930\u2009ml). The CH2Cl2 solution was concentrated to 30\u2009ml, then 30% H2O2 (4.5\u2009ml, 40\u2009mmol) was added at 0\u2009\u00b0C and stirred for four hours. After another extraction with CH2Cl2 (3\u2009\u00d7\u200930\u2009ml), the organic phase was combined and dried with anhydrous Na2SO4. The solvent was removed in vacuo. The product was purified by flash column chromatography, affording 2.6\u2009g of white powder in 90% yield. 1H\u2009NMR (TMS, CDCl3, 400\u2009MHz): \u03b4\u2009=\u20097.708\u20137.612 (m, 4H), 7.591\u20137.519 (m, 2H), 7.515\u20137.390 (m, 5H), 7.319\u20137.270 (m, 1H), 7.115 (t, J\u2009=\u20097.2\u2009Hz, 1H), 6.998 (q, J1\u2009=\u200913.6\u2009Hz, J2\u2009=\u20097.2\u2009Hz, 1H), 2.453\u2009ppm (s, 3H). Laser desorption\/ionization time-of-flight (LDI-TOF): m\/z (%): 292.10 (100) [M+]; elemental analysis (%) for C19H17OP: C 78.07, H 5.86, O 5.47; found: C 78.09, H 5.89, O 5.50.<\/p>\n
The synthetic procedure was similar to that of TPPOM except for using 4-bromo-1-iodo-2-methylbenzene (2.959\u2009g, 10\u2009mmol) instead of 1-bromo-2-methylbenzene. The product yielded 3.3\u2009g of white powder (90% yield). 1H\u2009NMR (TMS, DMSO-d6, 400\u2009MHz): \u03b4\u2009=\u20097.680\u20137.605 (m, 3H), 7.604\u20137.525 (m, 8H), 7.489 (d, J\u2009=\u20098.0\u2009Hz, 1H), 6.857 (q, J1\u2009=\u200913.2\u2009Hz, J2\u2009=\u20098.4\u2009Hz, 1H), 2.288\u2009ppm (s, 3H). LDI-TOF: m\/z (%): 370.01 (100) [M+]; elemental analysis (%) for C19H16BrOP: C 61.48, H 4.34, O 4.31; found: C 61.50, H 4.36, O 4.35.<\/p>\n
Under an argon atmosphere, TPPOMBr (1.856\u2009g, 5\u2009mmol), carbazole (2.508\u2009g, 15\u2009mmol), CuI (0.095\u2009g, 0.5\u2009mmol) and K2CO3 (2.073\u2009g, 15\u2009mmol) were dissolved in 50\u2009ml of 1,3-dimethyl-2-imidazolidinone (DMI) and heated to 190\u2009\u00b0C for 12\u2009h. After cooling to room temperature, the mixture was poured into water and extracted with dichloromethane (3\u2009\u00d7\u200910\u2009ml) again. The organic layers were combined and dried with anhydrous Na2SO4 and the solvent was removed in vacuo. The crude product was purified by column chromatography, affording 1.8\u2009g of white powder (80% yield). 1H\u2009NMR (TMS, DMSO-d6, 400\u2009MHz): \u03b4\u2009=\u20098.231 (d, J\u2009=\u20097.6\u2009Hz, 2H), 7.753\u20137.694 (m, 3H), 7.693\u20137.643 (m, 4H), 7.644\u20137.577 (m, 4H), 7.542 (d, J\u2009=\u20098.0\u2009Hz, 1H), 7.497 (d, J\u2009=\u20098.0\u2009Hz, 2H), 7.411 (t, J\u2009=\u20097.6\u2009Hz, 2H), 7.279 (t, J\u2009=\u20097.2\u2009Hz, 2H), 7.209 (q, J1\u2009=\u200913.6\u2009Hz, J2\u2009=\u20098.4\u2009Hz, 1H), 2.432\u2009ppm (s, 3H). LDI-TOF: m\/z (%): 457.16 (100) [M+]; elemental analysis (%) for C31H24NOP: C 81.38, H 5.29, N 3.06, O 3.50; found: C 81.39, H 5.30, N 3.08, O 3.54.<\/p>\n
The synthetic procedure was similar to that of CzPPOM except for using 3,6-di-tert-butyl-carbazole (4.188\u2009g, 15\u2009mmol) instead of carbazole. The yield was 2.2\u2009g of white powder (80% yield). 1H\u2009NMR (TMS, CDCl3, 400\u2009MHz): \u03b4\u2009=\u20098.138 (s, 2H), 7.711 (q, J1\u2009=\u200911.6\u2009Hz, J2\u2009=\u20097.6\u2009Hz, 4H), 7.480 (s, 1H), 7.448\u20137.332 (m, 10H), 7.299 (d, J\u2009=\u20098.0\u2009Hz, 1H), 7.220 (q, J1\u2009=\u200913.2\u2009Hz, J2\u2009=\u20098.0\u2009Hz, 1H), 2.515 (s, 3H), 1.385\u2009ppm (s, 18H). LDI-TOF: m\/z (%): 569.28 (100) [M+]; elemental analysis (%) for C39H40NOP: C 82.22, H 7.08, N 2.46, O 2.81; found: C 82.25, H 7.07, N 2.50, O 2.83.<\/p>\n
In an argon atmosphere, tris(dibenzylideneacetone)dipalladium (0.366\u2009g, 0.4\u2009mmol) and (t-Bu)3P (0.094\u2009ml, 0.4\u2009mmol) were mixed in toluene (10\u2009ml) and stirred for 20\u2009min at room temperature. TPPOMBr (3.700\u2009g, 10\u2009mmol), 9,9-dimethyl-9,10-dihydroacridine (DMAC, 2.509\u2009g, 12\u2009mmol), t-BuONa (1.922\u2009g, 20\u2009mmol) were added and the mixture was heated to 90\u2009\u00b0C and stirred for six hours. After the reaction, the toluene solvent was removed by distillation and the solid was dissolved in dichloromethane. The crude product was purified by flash column chromatography, yielding 3.9\u2009g of pale-yellow powder (80% yield). 1H\u2009NMR (TMS, CDCl3, 400\u2009MHz): \u03b4\u2009=\u20097.739 (q, J1\u2009=\u200912.0\u2009Hz, J2\u2009=\u20096.8\u2009Hz, 4H), 7.581 (t, J\u2009=\u20097.2\u2009Hz, 2H), 7.570\u20137.499 (m, 4H), 7.438 (dd, J1\u2009=\u20097.6\u2009Hz, J2\u2009=\u20091.2\u2009Hz, 2H), 7.305\u20137.267 (m, 1H), 7.268\u20137.215 (m, 1H), 7.120 (d, J\u2009=\u20098.0\u2009Hz, 1H), 6.978 (t, J\u2009=\u20097.2\u2009Hz, 2H), 6.920 (t, J\u2009=\u20097.2\u2009Hz, 2H), 6.266 (d, J\u2009=\u20098.0\u2009Hz, 2H), 2.519 (s, 3H), 1.667\u2009ppm (s, 6H). LDI-TOF: m\/z (%): 499.21 (100) [M+]; elemental analysis (%) for C34H30NOP: C 81.74, H 6.05, N 2.80, O 3.20; found: C 81.75, H 6.06, N 2.84, O 3.22.<\/p>\n
The synthetic procedure was similar to that of DMACPPOM except for using 9,9-diphenyl-9,10-dihydroacridine (DPAC, 3.998\u2009g, 12\u2009mmol) instead of DMAC. The reaction yielded 4.9\u2009g of white powder with an 80% yield. 1H\u2009NMR (TMS, CDCl3, 400\u2009MHz): \u03b4\u2009=\u20097.689 (q, J1\u2009=\u200912.0\u2009Hz, J2\u2009=\u20097.2\u2009Hz, 4H), 7.567 (t, J\u2009=\u20097.2\u2009Hz, 2H), 7.550\u20137.464 (m, 4H), 7.291\u20137.193 (m, 6H), 7.126 (q, J1\u2009=\u200913.6\u2009Hz, J2\u2009=\u20098.0\u2009Hz, 1H), 7.112\u20137.039 (m, 2H), 7.004\u20136.927 (m, 5H), 6.922\u20136.843 (m, 5H), 6.425 (d, J\u2009=\u20098.0\u2009Hz, 2H), 2.444\u2009ppm (s, 3H). LDI-TOF: m\/z (%): 623.24 (100) [M+]; elemental analysis (%) for C44H34NOP: C 84.73, H 5.49, N 2.25, O 2.57; found: C 84.74, H 5.51, N 2.28, O 2.60.<\/p>\n
Powdered KMnO4 (3.161\u2009g, 20\u2009mmol) was added in four portions over 1.5\u2009h to a boiling mixture of diphenyl(o-tolyl)phosphine oxide (TPPOM) (1.461\u2009g, 5\u2009mmol), pyridine (25\u2009ml) and water (10\u2009ml), maintaining gentle boiling throughout. The mixture was boiled for 5\u2009h, after which pyridine and water were removed by distillation. On cooling to room temperature, 1\u2009ml (6\u2009mmol\u2009ml\u22121) of hydrochloric acid in 10\u2009ml of H2O was added dropwise and stirred for 30\u2009min. The mixture was extracted with water and chloroform (3\u2009\u00d7\u200910\u2009ml). The organic layers were combined and dried with anhydrous Na2SO4. The solvent was removed in vacuo. The crude product was purified by column chromatography, yielding 1.1\u2009g of white powder with a yield of 70%. 1H\u2009NMR (TMS, DMSO-d6, 400\u2009MHz): \u03b4\u2009=\u200913.086 (s, 1H), 7.904\u20137.845 (m, 1H), 7.701 (t, J\u2009=\u20097.6\u2009Hz, 1H), 7.628 (t, J\u2009=\u20097.6\u2009Hz, 1H), 7.610\u20137.539 (m, 5H), 7.539\u20137.455\u2009ppm (m, 6H). LDI-TOF: m\/z (%): 322.08 (100) [M+]; elemental analysis (%) for C19H15O3P: C 70.81, H 4.69, O 14.89; found: C 70.83, H 4.69, O 14.91.<\/p>\n
The synthetic procedure was analogous to that of TPPOA but with the substitution of CzPPOM (2.286\u2009g, 5\u2009mmol) for TPPOM. The reaction produced 0.9\u2009g of white powder with a 40% yield. 1H\u2009NMR (TMS, DMSO-d6, 400\u2009MHz): \u03b4\u2009=\u200913.386 (s, 1H), 8.256 (d, J\u2009=\u20097.6\u2009Hz, 2H), 8.090 (t, J\u2009=\u20092.0\u2009Hz, 1H), 7.975 (d, J\u2009=\u20098.4\u2009Hz, 1H), 7.762 (q, J1\u2009=\u200912.8\u2009Hz, J2\u2009=\u20098.4\u2009Hz, 1H), 7.738\u20137.645 (m, 4H), 7.642\u20137.588 (m, 2H), 7.588-7.510 (m, 6H), 7.447 (t, J\u2009=\u20097.6\u2009Hz, 2H), 7.314\u2009ppm (t, J\u2009=\u20097.6\u2009Hz, 2H). LDI-TOF: m\/z (%): 487.13 (100) [M+]; elemental analysis (%) for C31H22NO3P: C 76.38, H 4.55, N 2.87, O 9.85; found: C 76.39, H 4.57, N 2.89, O 9.88.<\/p>\n
The synthetic procedure was similar to that of TPPOA except for using tBCzPPOM (2.846\u2009g, 5\u2009mmol) instead of TPPOM. The reaction yielded 1.2\u2009g of white powder with a 40% yield. 1H\u2009NMR (TMS, DMSO-d6, 400\u2009MHz): \u03b4\u2009=\u200913.359 (s, 1H), 8.324 (s, 2H), 8.077 (s, 1H), 7.977 (d, J\u2009=\u20096.8\u2009Hz, 1H), 7.821\u20137.720 (m, 1H), 7.718\u20137.631 (m, 4H), 7.629\u20137.527 (m, 6H), 7.525\u20137.424 (m, 4H), 1.416\u2009ppm (s, 18H). LDI-TOF: m\/z (%): 599.26 (100) [M+]; elemental analysis (%) for C39H38NO3P: C 78.11, H 6.39, N 2.34, O 8.00; found: C 78.13, H 6.37, N 2.37, O 8.03.<\/p>\n
The synthetic procedure was similar to that of TPPOA except that DMACPPOM (2.496\u2009g, 5\u2009mmol) was used instead of TPPOM. The reaction gave 1.0\u2009g of pale-yellow powder with a 40% yield. 1H\u2009NMR (TMS, CDCl3, 400\u2009MHz): \u03b4\u2009=\u20098.392 (s, 1H), 7.750\u20137.548 (m, 9H), 7.545\u20137.432 (m, 5H), 7.324\u20137.254 (m, 2H), 7.252\u20137.175 (m, 2H), 7.128 (t, J\u2009=\u20097.2\u2009Hz, 1H), 7.036 (d, J\u2009=\u20097.6\u2009Hz, 1H), 1.486\u2009ppm (s, 6H). LDI-TOF: m\/z (%): 529.18 (100) [M+]; elemental analysis (%) for C34H28NO3P: C 77.11, H 5.33, N 2.64, O 9.06; found: C 77.11, H 5.32, N 2.67, O 9.08.<\/p>\n
The synthetic procedure was similar to that of TPPOA except that DMACPPOM (3.116\u2009g, 5\u2009mmol) was used instead of TPPOM. The reaction yielded 1.3\u2009g of white powder with a 40% yield. 1H\u2009NMR (TMS, CDCl3, 400\u2009MHz): \u03b4\u2009=\u20098.097 (s, 1H), 7.652\u20137.527 (m, 6H), 7.524\u20137.423 (m, 4H), 7.294\u20137.165 (m, 6H), 7.106 (t, J\u2009=\u20097.2\u2009Hz, 2H), 7.028 (q, J1\u2009=\u200914.0\u2009Hz, J2\u2009=\u20098.0\u2009Hz, 1H), 7.000\u20136.854 (m, 9H), 6.572\u2009ppm (d, J\u2009=\u20098.0\u2009Hz, 2H). LDI-TOF: m\/z (%): 653.21 (100) [M+]; elemental analysis (%) for C44H32NO3P: C 80.84, H 4.93, N 2.14, O 7.34; found: C 80.86, H 4.92, N 2.16, O 7.38.<\/p>\n
To prepare the ligand salt solution, sodium hydroxide (0.002\u2009g, 0.05\u2009mmol) in 1\u2009ml of ethanol was added into a mixture of 0.05\u2009mmol of ligand in 2\u2009ml of ethanol. This ligand salt solution was then combined with an ethanol solution containing ligand-free nanocrystals (0.001\u2009mmol) and the mixture was ultrasonicated for two hours to ensure proper ligand coordination of the ligands to nanocrystal surfaces. Any excess ligand was removed by centrifugation and the resulting product was redispersed in ethanol for optical measurements or in DMF for device fabrication.<\/p>\n
Tb(ligand)3 complexes were prepared according to established protocols33. ArPPOA (3\u2009mmol) was dissolved in 10\u2009ml of ethanol and NaOH (0.120\u2009g, 3\u2009mmol) in aqueous solution (1\u2009M) was added to deprotonate ArPPOA. TbCl3\u00b76H2O (0.373\u2009g, 1\u2009mmol) in 0.1\u2009ml of water was added dropwise, then the solution was stirred at 60\u2009\u00b0C for two hours. The product was purified by precipitation using a concentrated ethanol\u2013water solution.<\/p>\n
The device structure consisted of: ITO|PEDOT:PSS (40\u2009nm)|PVK (20\u2009nm)|mCP:y\u2009wt% NaGd0.6F4:Tb0.4\u2212xEux@ligand (25\u2009nm)|DPEPO (10\u2009nm)|TmPyPB (40\u2009nm)|LiF (1\u2009nm)|Al (100\u2009nm). In this configuration, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and LiF serve as the hole and electron injection layers, respectively, whereas the other materials, including polyvinylcarbazole (PVK), 1,3-bis(N-carbazolyl)benzene (mCP), bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) and 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene (TmPyPB), function as hole transporting, host, exciton blocking and electron transporting layers, respectively. Further host materials such as bis-4-(N-carbazolyl)phenyl)phenylphosphine oxide (BCPO), 4,4\u2032-bis(9H-carbazol-9-yl)biphenyl (CBP), 4,4-bis(9-carbazolyl)-2,2-dimethylbiphenyl (CDBP), CPPOM, 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi), DPEPO and PVK were also used for comparison. The PEDOT:PSS layer was spin-coated on a patterned ITO-coated glass substrate after oxygen plasma treatment. To remove any residual water, the PEDOT:PSS layer was baked at 120\u2009\u00b0C for 20\u2009min in a glovebox. The PVK layer was then spin-coated from a 10\u2009mg\u2009ml\u22121 DMF solution onto the PEDOT:PSS layer and baked at 70\u2009\u00b0C for 15\u2009min. The emitting layer, also spin-coated from DMF at a concentration of 10\u2009mg\u2009ml\u22121, was similarly baked at 70\u2009\u00b0C for 15\u2009min. After spin-coating, the sample was transferred to a high-vacuum evaporation system. The electron transporting layers were sequentially evaporated at a rate of 0.1-0.2\u2009nm\u2009s\u22121 under a pressure less than 4\u2009\u00d7\u200910\u22124\u2009Pa. A 1-nm-thick LiF layer was deposited at 0.1\u2009nm\u2009s\u22121 to improve electron injection, followed by a 100-nm-thick Al cathode deposited at 0.6\u2009nm\u2009s\u22121. The emission area of the devices was 0.09\u2009cm2, defined by the overlap of the anode and cathode. Post-fabrication, all devices were encapsulated with ultraviolet epoxy resin in the glovebox before undergoing luminance\u2013current\u2013voltage measurements. Emission intensity was measured with a calibrated Si photodiode and the external quantum efficiency was calculated assuming a Lambertian distribution. The electroluminescent spectrum was recorded using a calibrated PR-655 spectrometer.<\/p>\n
Absorption spectra in the near-infrared range were measured at room temperature using a Shimadzu ultraviolet\u2013visible\u2013near-infrared spectrophotometer (UV-3600). PL spectra were recorded at room temperature using a DM150i monochromator and an R928 photon-counting photomultiplier tube, in conjunction with a 980-nm diode laser. Decay curves were measured with a custom ultraviolet-to-mid-infrared phosphorescence lifetime spectrometer (FLS1000, Edinburgh) equipped with a digital oscilloscope (TDS3052B, Tektronix) and a tunable optical parametric oscillator laser (410\u20132,400\u2009nm, Vibrant 355 II, OPOTEK) as the excitation source.<\/p>\n
Transient absorption spectra were recorded using a pump\u2013probe set-up. Samples were excited by tunable pump pulses (355\u20132,600\u2009nm) generated from an optical parametric amplifier, pumped by a regenerative Ti:sapphire amplifier (Coherent; 800\u2009nm, 100\u2009fs, 7\u2009mJ per pulse, 1\u2009kHz repetition rate). Broadband probe pulses were generated by focusing a portion of the Ti:sapphire output onto a sapphire crystal or YAG crystal, producing light spanning 350\u20131,550\u2009nm. For short-time measurements (500\u2009fs to 7\u2009ns), a commercial spectrometer (HELIOS, Ultrafast Systems) was used, with probe ranges of 350\u2013800\u2009nm and 750\u20131,600\u2009nm. Long-time measurements (1\u2009ns to 1\u2009ms) used probe ranges of 410\u2013750\u2009nm and 850\u20131,600\u2009nm. A computer-controlled motorized delay stage was used to vary the probe path length. The pump beam was modulated at 500\u2009Hz using a chopper, generating alternating probe pulses with and without excitation. Both beams were focused to an approximately 0.5-mm2 spot on the sample. The instrument response function was approximately 200\u2009fs.<\/p>\n
PL decay kinetics within a 7-ns window were recorded using a femtosecond sum-frequency upconversion apparatus (HALCYONE, Ultrafast Systems) powered by a regenerative Ti:sapphire amplifier (Coherent; 800\u2009nm, 100\u2009fs, 7\u2009mJ per pulse, 1\u2009kHz repetition rate). The 800-nm beam was split: one portion pumped an optical parametric amplifier to produce tunable excitation pulses and the other served as the gate pulse. Emission from the sample was collected and co-focused with the 800-nm gate pulse onto a barium metaborate crystal, generating an upconverted signal by means of sum-frequency generation. This signal was passed through a 300-mm monochromator and detected by a spectrometer, providing a temporal resolution of 250\u2009ps. All measurements were conducted on samples sealed in 2-mm airtight cuvettes, placed in a nitrogen-filled glovebox under continuous agitation.<\/p>\n","protected":false},"excerpt":{"rendered":"
Materials and instruments All reagents and solvents used for the synthesis of the compounds were purchased from Aldrich and Acros companies and used without further purification. 1H nuclear magnetic resonance (NMR) spectra were recorded using a Varian Mercury plus 400NB spectrometer, with tetramethylsilane (TMS) as the internal standard. Molecular masses were determined using a FINNIGAN<\/p>\n","protected":false},"author":1,"featured_media":34478,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[19589,19593,19590,19592,19591],"class_list":{"0":"post-34477","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-electrogenerated","9":"tag-electroluminescence","10":"tag-excitons","11":"tag-lanthanide","12":"tag-tunable"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/34477","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=34477"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/34477\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/34478"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=34477"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=34477"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=34477"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}