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The synthesis of a phenoxy-benzothiadiazole (BTD) derivative is reported for the first time. This derivative was employed as an intermediate in the obtention of two novel highly fluorescent aryl-phenoxy-BTD dyes. Their photophysical properties were evaluated in solution and the results indicate a strong intramolecular charge transfer (ICT) character in the excited state. The luminophore 3a, possessing a donor-BTD-phenoxide architecture, exhibits superior fluorescence quantum yield (0.67) than the designed acceptor-BTD-phenoxide dye (0.06). After electrochemical and photoluminescence characterization of thin films of 3a, an OLED with the configuration ITO/PEDOT:PSS/3a/TPBi/LiF/Al was constructed. This device displayed a green emission centered at 547 nm, with CIE coordinates of (0.40, 0.55). For comparison, an OLED using a previously reported luminescent BTD-pyridyl derivative was also constructed. The OLED made with the phenoxy-BTD derivative operated using less current density and led to higher irradiance and electrical stability, indicating the high potential of ArO-BTD dyes for future application in electroluminescent devices.

An in situ reaction of two optoelectronically active organic ligands (anionic thenoyltrifluoroacetylacetone, tta−, and neutral triphenylphosphine oxide, tppo) with erbium(III) ion in the presence of a base yielded a new erbium complex, [Er(tta)3(tppo)]. The solid and solution structure of the complex was established by X-ray crystallography, NMR, ESI-MS, FTIR, TGA and Raman spectroscopy. They indicate that the Er(III) ion is coordinated to seven oxygen atoms of three tta ligands and one tppo ligand in a monocapped octahedral geometry. The Judd–Ofelt parameters of the complex were determined by a least squares fitting and dealt with its chemical structure. On UV excitation through ligand mediation, the complex shows the characteristic near-infrared emission of the corresponding Er(III) ion at 1534 nm. Furthermore, a near infra-red organic light emitting diode (NIR-OLED) was fabricated with structure: ITO/[N,N′-bis(naphthalen-2-yl)-N,N′-bis(phenyl)benzidine]/[Er(tta)3(tppo)]/[2,2′,2′′-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)]/LiF/Al. This device, with maximum applied voltage of 23 V, shows a total quenching of visible emission and electroluminescence in the C-band region (1534 nm) which is suitable for third communication window applications in fiber optics. Finally, an organic diode was fabricated to determine charge carrier mobility of the complex using a steady-state method.

A novel Er(III) β-diketonate complex, tris(dibenzoylmethanate)mono(triphenylphosphine oxide) erbium(III) or [Er(dbm)3(tppo)] was synthesised with dbm as a main sensitizer and tppo as a synergic ligand. The single crystal X-ray analysis reveals that the crystal structure of the complex is a triclinic centrosymmetric where Er(III) ion is coordinated to seven oxygen atoms; one O-atom from one tppo and six O-atoms from three dbm ligands. Shape-measure criterion measurements show that the complex possesses a distorted monocapped octahedron geometry, which facilitates the radiative transitions that is an indicative of efficient energy transfer from coordinated ligands to Er ion. The crystal structure is stabilised by the π–π stacking and CH/π interactions which lead to its high photo- and thermal stabilities. The complex was doped into a polymer matrix and the resulted material shows an enhanced luminescence intensity as well as full width at half maximum (fwhm) which allow its possible use for optical-amplification applications. Finally, a single layered organic diode was fabricated to determine charge carrier mobility (μ0) inside the complex. For this purpose, the Mott–Gurney model was used which gave sizable μ0 of 3.39 × 10−9 cm2/Vs (at

A low symmetry NIR emitting ytterbium (III) β-diketonate ternary complex with composition, [Yb(tta)3(tppo)]·H2O (tta = thenoyltrifluoroacetylacetone and tppo = triphenyl phosphine oxide) was synthesized and fully characterized. Single crystal X-ray analysis and shape measurement calculations indicate that the complex is a seven-coordinate and possesses distorted trigonal prism geometry with coordination polyhedra YbO7 where the Yb(III) ion is surrounded by seven oxygen atoms of three tta and one tppo ligands. It is a highly asymmetric structure enhancing the radiative transitions which is an indicative of efficient energy transfer from coordinated ligands to Yb ion. The complex was doped in a tris(4-carbazoyl-9-ylphenyl)amine (TcTa) matrix and used as an emitting layer to fabricate near-infrared organic light emitting device (NIR-OLED) with the structure: ITO/{N,N′-bis(naphtalen-2-yl)-N,N′-bis(phenyl) benzidine} (25 nm)/[Yb-complex] (10%): TcTa (40 nm)/BCP (15 nm)/Alq3 (10 nm)/LiF (0.5 nm)/Al (120 nm). The complex based NIR-OLED showed good EL efficiency with maximum irradiance of 19.29 μW/cm2 and current density of 27.3 mA/cm2 at 15 V. In view of electrical characteristics, the charge carrier mobility, μ0, of the complex was determined by using Mott–Gurney model which gave a sizable value of 4.50 × 10−8 cm2/Vs.

Efficient light detection in the near-infrared (NIR) wavelength region is central to emerging applications such as medical imaging and machine vision. An organic upconverter (OUC) consists of a NIR-sensitive organic photodetector (OPD) and an visible organic light-emitting diode (OLED), connected in series. The device converts NIR light directly to visible light, allowing imaging of a NIR scene in the visible. Here, we present an OUC composed of a NIR-selective squaraine dye-based OPD and a fluorescent OLED. The OPD has a peak sensitivity at 980 nm and an internal photon-to-current conversion efficiency of ∼100%. The OUC conversion efficiency (0.27%) of NIR to visible light is close to the expected maximum. The materials of the OUC multilayer stack absorb very little light in the visible wavelength range. In combination with an optimized semitransparent metal top electrode, this enabled the fabrication of transparent OUCs with an average visible transmittance of 65% and a peak transmittance of 80% at 620 nm. Visibly transparent OUCs are interesting for window-integrated electronic circuits or imaging systems that allow for the simultaneous detection of directly transmitted visible and NIR upconverted light.