Efficient near ultraviolet light-emitting materials are of particular importance in organic light emitting devices (OLEDs) because of its impending application in high-quality flat panel displays and white OLEDs. In the...

Three ancillary ligands based on imidazo-bipyridyl with phenyl (Ph), naphthyl (Np), and triphenylamine (TPA) substitution were synthesized and secondhand to formulate the consistent europium(III) ternary complexes using thenoyltrifluoroacetone as an anionic ligand. The complete investigation of spectroscopic, photophysical, and electrochemical properties was carried out. The attained results for all the ancillary ligands and their corresponding Eu complexes were compared with one another. All the Eu complexes reveal a broad excitation band ranging from the near-UV to blue region, along with high intense emission and apposite color purity. To further understand the ligand-to-metal energy transfer (ET) process, the geometry of the ligand was optimized and the energy level location (singlet and triplet) was calculated by using DFT and TD-DFT calculations. On the basis of the theoretical calculation, the ET mechanism was proposed. From PL emission spectra in the solid state, complete ET occurs from Ph, Np based ancillary ligands to the Eu ion, which yields a pure red emission, whereas the TPA functionalized based Eu complex shows incomplete ET. Fortunately, white emission was observed in the TPA based Eu complex in the solid state. The white LED was fabricated by using a white emitting complex integrated with 395 nm emitted LED (InGaN) chips under 20 mA forward-bias current. The excitation source from LED was fully observed by the complex shown for 3Eu and showed yellowish emission in different concentrations (the similar observation also reflected in solid). However, in the case of 1Eu and 2Eu complexes, they showed close to white emission. The Commission International de I'Eclairage (CIE) chromaticity coordinates are close to the National Television Standard Committee standard value for white emission, and in addition, the complex 3Eu coated with the blue LED chip (460 nm) by PMMA (1:10) showed bright white emission with CIE x, y values of 0.30, 0.33, respectively.

A carbazole functionalized phenanthroimidazole based bipolar ligand consisting of a β-diketonate Eu(iii) complex shows efficient energy transfer and QE (11.5%) with appropriate CIE color coordinates (x = 0.66, y = 0.33).

The new bipolar ligand 4‐{1‐(9,9‐diethyl‐9H‐fluoren‐2‐yl)‐1H‐imidazo[4,5‐f][1,10]phenanthrolin‐2‐yl}‐N,N‐diphenylbenzenamine (Phen‐Fl‐TPA) and its β‐diketonate EuIII complex have been designed, synthesized, characterized, and their photophysical and electrochemical properties have been investigated. The UV/Vis absorption and photoluminescence (PL) emission spectra of the Eu complex and Phen‐Fl‐TPA in solution as well as in the solid state and as thin films were recorded. The PL study indicated that the Eu complex emits narrow‐band red emission with an appropriate International Commission on Illumination (CIE) color gamut. Moreover, it also confirmed the efficient energy transfer from the ligand to the Eu3+ ion. Time‐dependent DFT (TD‐DFT) calculations were performed for the ligand to determine the exact positions of the excited singlet and triplet energy levels. The EuIII complex shows a dominant pathway involving energy transfer between the ligand triplet level and the excited (5D0) level of the EuIII ion. In addition, the theoretically calculated UV/Vis spectrum of the ligand is similar to the experimental one. The Judd–Ofelt theory was applied to the emissive properties of the EuIII complex, and the lifetime was found to be 0.66 ms. The ground‐state optimized ligand structure was a good match with the single‐crystal structure. The photoluminescence quantum yield (PLQY) of Eu(TTA)3Phen‐Fl‐TPA (TTA = thenoyltrifluoroacetone) in solution was 34.1 %, and it possess a high thermal decomposition temperature (317 °C), as determined by differential scanning calorimetry/thermogravimetric analysis (DSC‐TGA). Electrochemical analysis revealed highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels for the EuIII complex of 5.6 and 2.8 eV, respectively.

Dual emissive single-component white light emissive luminogens are promising color convertors for white light emitting diodes. In this context, a new class of bipolar phenanthroimidazole based (N1 functionalization with Ph,...