Innovative materials for phosphor converted white light-emitting diodes are in high demand owing to the huge potential of the light-emitting diode technology to reduce energy consumption worldwide. As the primary blue diode is already highly optimized, the conversion phosphors are of crucial importance for any further improvements. We report on the discovery of the high performance red phosphor Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ meeting all requirements for a phosphor’s optical properties. It combines the optimal spectral position for a red phosphor, as defined in the 2016 Research & Development-plan of the United States government, with an exceptionally small spectral full width at half maximum and excellent thermal stability. A white mid-power phosphor-converted light-emitting diode prototype utilising Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ shows an increase of 16% in luminous efficacy compared to currently available commercial high colour-rendering phosphor-converted light-emitting diodes, while retaining excellent high colour rendition. This phosphor enables a big leap in energy efficiency of white emitting phosphor-converted light-emitting-diodes.

850 1090A uniform array of gallium nitride core-shell microrod (MR) lightemitting diode (LED) structures was grown by metalorganic vapor phase epitaxy. Defects and the quantum well (QW) luminescence in an individual rod were investigated by scanning tunneling electron microscopy (STEM) and STEM cathodoluminescence. Luminescence with different wavelength was detected from the quantum wells on the semipolar tip facets and the nonpolar sidewalls of the MRs. Furthermore, the MR array is processed into LED chips. The electro-optical characteristics of the devices are analyzed. Two separate emission bands are distinguished, which are attributed to the QWs on the semipolar tip facets and the nonpolar sidewalls, respectively. To obtain white LEDs, micrograin phosphors were developed which fit in between individual MRs. By using electrophoretic particle deposition, these phosphors are deposited onto the MR LED chips. Color coordinates, color temperature, and device efficiency are evaluated.Blue (top) and phosphor-converted white (bottom) microrod LEDs on 4 00 wafer.

We synthesised a new N-benzylaza-21-crown-7 ether 5 with a dihydroxy coumarin as a fluorescence sensor and investigated the binding behaviour towards alkali metal cations in methanol by fluorescence titrations. The association constants are within one order of magnitude, with the exception of sodium. Potassium is the preferred binding partner (K(Na)=330 M(-1); K(K)=8600 M(-1); K(Rb)=8200 M(-1); K(Cs)=4400 M(-1)). The corresponding aza-21-crown-7 ether (6) was attached by a methylene unit to a resorcarene to give fluorescent calix crown ether 12. The binding abilities of the calix crown ether towards alkali metal ions in methanol have also been investigated, and an increasing complex stability, distinct for potassium and rubidium in comparison with 5, was found: K(Na)=440 M(-1); K(K)=110,000 M(-1); K(Rb)=63,000 M(-1); K(Cs)=20,000 M(-1). Like bis(crown ether)s, a cooperative complexation of the crown ether and the cavitand scaffold can be assumed. The proposed complex geometry is supported by Kohn-Sham DFT calculations for the potassium and caesium complexes.

Solution processing methods of conjugated polymers are an important strategy for the preparation of organic semiconductors. We introduce a novel family of semiconductors prepared by the solution based small molecule self-assembly of 2-amino-5-pentafluorophenylpyrimidine and various silver(I) salts (AgX; X = CO 2 CF 3 , SO 3 CF 3 , NO 3 ). The compounds are analyzed by single crystal analysis revealing that the solid state assembly consists of alternating polymer strands of 2-aminopyrimidine and silver(I).The solid state assembly can be controlled by the silver counterion and the solvent yielding polymer strands with different interatomic parameters and optoelectrical properties. The compounds are optically characterized and reveal remarkably different solid state absorption when compared to the parent compound 2-aminopyrimidine in solution. Also, an exclusive solid state emissive state is observed. Herein, the excitation occurs not at the maximum but at the onset of absorbance. The silver(I)triflate-2-aminopyrimidine yields two different porous frameworks depending on the solvent used for crystallization. These porous frameworks are made of 1-dimensional polymer strands, and the pores are filled with solvent molecules. By heating and addition of solvent the frameworks can be reversibly converted into each other in the solid state, changing the optoelectrical properties. The compounds are thermodynamically analyzed by differential scanning calorimetry. Also, the electrical conductance was proven in a preliminary experiment on a thin crystalline film of 4.

Calculations based on (occupation constrained) density functional theory using local as well as hybrid functionals to describe the electron-electron exchange and correlation are combined with many-body perturbation theory in order to determine and rationalize the electronic and optical excitation properties of 2-aminopyrimidinesilver(I) based organic semiconductors and their parent molecules. Large quasiparticle shifts and exciton binding energies of about 4 eV are found in the aminopyrimidine molecules. Both the quasiparticle blueshift and the excitonic redshift are reduced upon crystal formation. They cancel each other partially and thus allow for a meaningful description of the molecular and crystal optical response within the independent-particle approximation. We find a surprisingly strong influence of local-field effects as well as resonant-nonresonant coupling terms in the electron-hole Hamiltonian on the optical properties. The calculations reproduce well measured data and allow for identifying chemical trends with respect to the organic building blocks of the crystals.