Alexey N. Konev

Near-infrared electroluminescent lanthanide [Pr(III), Nd(III), Ho(III), Er(III), Tm(III), and Yb(III)] N,O-chelated complexes for organic light-emitting devices

New near-IR electroluminescent complexes of Pr3+, Nd3+, Ho3+, Er3+, Tm3+, Yb3+ with N,O-chelated ligands, Ln2(OON)6 (OON = 2-(2-benzoxyazol-2-yl)phenolate) and Ln2(SON)6 (SON = 2-(2-benzothiazol-2-yl)phenolate), were synthesized by the reaction of Ln[N(SiMe3)2]3 and the corresponding N,O-chelating ligand. X-Ray analysis for the Pr and Nd compounds reveals centrosymmetric dimeric structures of the complexes. The solid-state electronic absorption spectra and the electroluminescent spectra show long-wavelength 4f–4f transitions which provide potential use of the compounds as NIR emitting materials in organic light-emitting devices (OLEDs). When constructing OLEDs based on Ln2(OON)6 and Ln2(SON)6, the best results were achieved with the Nd3+ and Yb3+ complexes, where the NIR wall plug efficiency of the ITO/TPD/Ln-complex/BATH/Yb system is 0.82 and 1.22 mW W−1, respectively.

Electroluminescent properties of lanthanide pentafluorophenolates

Lanthanide pentafluorophenolates Ln(OC6F5)3(L)x (Ln = Pr, Nd, Sm, Eu, Dy, Ho, Er, Yb; L = 1,10-phenanthroline, 2,2′-bipyridine; x = 1 and 2) are used as emissive layers in organic light emitting devices (OLEDs). Single-layer ITO/Ln(OC6F5)3(L)x/Yb devices reveal no electroluminescence (EL) with the exception of Tb-derivative-based OLEDs. Bilayer ITO/TPD/Ln(OC6F5)3(L)x/Yb samples exhibit a broad band emission peaked at 580 nm assigned to an electroplex at the TPD/complex interface. Besides, the spectra of the devices based on Pr, Nd, Sm, Eu, Er, Tb and Yb derivatives contain the characteristic narrow bands of f–f transitions. Terbium-based bilayer OLEDs exhibit unusual changes in the EL spectra with increasing the applied voltage. The emission color of the devices tunes from orange towards green. The possible nature of the phenomenon is discussed.

Electroluminescent characteristics of scandium and yttrium 8-quinolinolates

Efficient electroluminescence (EL) was obtained in organic light-emitting devices using 8-quinolinolate complexes of scandium (Scq3) and yttrium (Yq3) as emitters. Compared to the device based on the analogous Alq3 complex, no notable difference in the EL performances of the Yq3 device can be found; however, the EL characteristics of device with Scq3 were significantly enhanced. The device with the configuration of indium tin oxide/ N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine/Scq3/Yb exhibits a maximum current efficiency of 4.6 cd/A and a maximum power efficiency of 2.6 lm/W at a luminance of 300 cd/m2. The improvement of the performance of this device should be attributed to the higher hole mobility of the Scq3 as compared to Alq3 or a smaller barrier for hole injection into Scq3 compared to Alq3.

Biraite-(Ce), Ce2Fe 2+(CO3)(Si2O7), a new mineral from Siberia with a novel structure type

Biraite-(Ce), ideally Ce 2 Fe 2+ (CO 3 )(Si 2 O 7 ), has been found in the Biraia deposit (Irkutsk district, Russia), associated with cordylite-(Ce) and -(La), aragonite, strontianite, Sr,Fe- bearing dolomite, ancylite-(Ce) and -(La), hydroxy 1 -bastnasite-(Ce), daqingshanite-(Ce) and -(La), tremolite, winchite, ferriallanite-(Ce), tornebohmite-(Ce), cerite, chevkinite-(Ce), belkovite, humite, fergusonite-(Ce) and -(Nd), pyrochlore, barite, monazite-(Ce) and other unknown minerals. Biraite-(Ce) occurs as irregular to well-shaped grains from 0.1 to 3 mm in length, has brown colour with a white streak, is semi-transparent with a vitreous luster and brittle.The hardness (Mohs) is 5, and the calculated density is 4.76 g/cm 3 . Optically, biraite-(Ce) is biaxial (-), with α 1.785(1),β 1.810(2),γ 1.820(1), 2V 66°(1). Electron microprobe and wet chemical analyses gave the following empirical formula based on 10 O+F:(Ce 1.01 La 0.57 Nd 0.25 Pr 0.09 Sm 0.02 Ca 0.07 Na 0.02 Ba 0.01 )Σ= 2.04 (Fe 0.60 Mg 0.25 Mn 0.11 Ti 0.01 )Σ=0.97 (CO 3 ) 0.99 [Si 1.97 (O 6.87 F 0.17 )Σ=7.04].The simplified formula is Ce 2 Fe 2+ (CO 3 )(Si 2 O 7 ). The IR spectrum confirmed the presence of [CO 3 ] groups. The strongest lines of the X-ray powder pattern [ d in A ( I ) ( hkl )] are: 3.30 (5) (021), 2.92 (10) (006, 21–2), 2.65 (5) (202, 12–4), 2.23 (5) (116, 031). Biraite-(Ce) is monoclinic, space group P 2 1 / c , with a 6.505(7), b 6.744(2), c 18.561(4) A,β 108.75(2)°. Its crystal structure was refined from single-crystal X-ray diffraction data to R(F) = 0.033. Biraite-(Ce) displays a new structure type, based on polyhedral (001) sheets composed of pairs of edge-sharing [FeO 6 ] octahedra, [Si 2 O 7 ] groups, and [CO 3 ] triangles. Ce 3+ cations in ten-fold coordination provide the linkage between neighbour polyhedral sheets. Both the mineral and its name have been approved by the IMA Commission on New Minerals and Mineral Names.

New cathode materials for organic light-emitting diodes: Tm:Yb and Eu:Yb

Performance characteristics of organic light-emitting diodes (OLEDs) with mono-(Al, Sm, Tm, Yb) and bimetallic (Ca:Al, Eu:Yb, Tm:Yb) cathodes are compared. It is shown that OLEDs with the Tm:Yb cathodes are the best of the studied devices in terms of the turn-on voltage, operating voltage, current efficiency, and luminance efficiency.

Synthesis of EuS and EuSe particles via thermal decomposition of dithio- and diselenophosphinate europium complexes

New two- and trivalent europium complexes with dithio- and diselenodiphenylphosphinate ligands (S2PPh2- and Se2PPh2-) have been synthesized as precursors for nanoparticles. Two-valent europium compounds have been characterized via X-ray diffraction. Their photoluminescence properties have been studied as well. EuS colloidal nanoparticles have been obtained via the thermolysis of Eu(S2PPh2)n (n = 2, 3) in a hexadecylamine medium at 310°C. The average size of objects is found to be 40–70 nm. As is established, the valent state of a lanthanide in the complex exerts no influence on the size of the forming nanoparticles or on the luminescence spectrum of colloidal solutions.