Crystal Structure,Fe^(3+) Luminescence Sensing and Color Tuning of 2D Lanthanide-metal-organic Frameworks Constructed from Tricarboxylic Acid Ligand

A new lanthanide metal-organic framework (MOF)[Eu(BTB)(phen)(DMF)]·DMF (1,DMF=N,N-dimethylformamide) was synthesized using H_(3)BTB (1,3,5-tri(4-carboxyphenyl)benzene) and phen(1,10-phenanthroline) under solvothermal conditions.The structure of the prepared MOF was characterized by single-crystal X-ray diffraction analyses,elemental analysis,fluorescence spectrum,FT-IR spectroscopy,powder X-ray diffraction and thermogravimetric analyses.The structure of 1 can be viewed as a 3-D supramolecular network,which is formed by the stacking of 2D layers throughπ-πinteraction.The luminescence explorations revealed that 1 possesses favorable selectivity and sensitivity for testing Fe^(3+).Additionally,color tuning was achieved by varying Eu^(3+):Tb^(3+)ratios in the reaction mixtures.

Emission Color Tuning with Polymer Molecular Weight for Dyes of 4-Dicyanomethylene-2-methyl-6-{4-[（2-hydroxy- ethyl）（methyl）amino]styryl}-4H-pyran

A series of novel polylactide （PLA） polymers were synthesized initiated by 4-dicyanomethylene- 2-methyl-6-{4-[（2-hydroxyethyl）（methyl）amino]styryl}-4H-pyran （DCM） with Sn（Oct）2 as catalyst. The color and emission of the polymer can be tuned just with polymer molecular weight.

Exciplex formation and properties at organic solid interface in organic light emitting devices

The bilayer organic light emitting devices （OLEDs） using two common aromatic diamines as hole transporting materials （HTMs） and BBOT （2,5-bis（5-tert-butyl-2-benzoxazolyl）thiophene） as electron transporting material have been prepared, in which the electroluminescent spectra are different from the fluorescent spectra of each of the constituent materials. The electroluminescence is mainly attributed to exciplex confirmed by photoluminescence and electroluminescence measurements, and the type of exicplex is deternfined in terms of the energy level diagram of the bilayer devices, By comparing the molecular structures and energy levels of TPD and NPB, it is demonstrated that the structure of a molecule as well as its energy level has an effect on the exciplex formation.

Blue Emission from Exciplex in Electroluminescent Devices Made from Vinyl Polymer and Oxadiazole Derivative

Two types of molecular and polymer devices employing (2-(4′-biphenyl)-5-(4″-tert-butylphenyl)-1,3,4-oxadiazole) (PBD) and poly(N-vinylcarbazole)(PVK) as electron transport and hole transport materials, respectively, have been fabricated. The structures of these two devices are ITO/PVK(70 nm)/PBD(60 nm)/Al and ITO/PVK∶PBD(1∶1 by mass, 70 nm)/Al. The formation of exciplex is evident by comparing the electroluminescence (EL) of a bi-layer device and the photoluminescence (PL) of a PVK and PBD mixed film. The maximum emission energy of exciplex evaluated is consistent with the peak emission of EL. Blue emissions from both devices are obtained. The type of exicplex is interpreted based on the energy level diagram of the bi-layer device.

Get it white: color-tunable AC/DC OLEDs

Organic light-emitting diodes(OLEDs)have gained considerable attention because of their use of inherently flexible materials and their compatibility with facile roll-to-roll and printing processes.In addition to high efficiency,flexibility and transparency,reliable color tunability of solid state light sources is a desirable feature in the lighting and display industry.Here,we demonstrate a device concept for highly efficient organic light-emitting devices whose emission color can be easily adjusted from deep-blue through cold-white and warm-white to saturated yellow.Our approach exploits the different polarities of the positive and negative half-cycles of an alternating current(AC)driving signal to independently address a fluorescent blue emission unit and a phosphorescent yellow emission unit which are vertically stacked on top of each other.The electrode design is optimized for simple fabrication and driving and allows for two-terminal operation by a single source.The presented concept for color-tunable OLEDs is compatible with application requirements and versatile in terms of emitter combinations.

Emission enhancement and color modulation of Tm(Ho)/Yb codoped Gd_(2)(MoO_(4))_(3) thin films via the use of multilayered structure

The multilayered structure thin films(Gd_(2)(MoO_(4))_(3):Ho(Tm)/Yb@Gd_(2)(MoO_(4))_(3):Yb) were prepared through sol-gel and spin-coating method,while the average thinness was nearly 140 nm.We investigated the up-conversion luminescence of Gd_(2)(MoO_(4))_(3):Ho(Tm)/Yb@Gd_(2)(MoO_(4))_(3):Yb thin films,The results show that the double-layer structured thin films are able to increase the emission intensity.The fluorescence enhancement factors of the luminescence from Gd_(2)(MoO_(4))_(3):Ho/Yb@Gd_(2)(MoO_(4))_(3):Yb thin films,located at540 and 662 nm,reach 7.5 and 4.3,respectively.And the enhancement factors of emissions located at450,475 and 650 nm(Gd_(2)(MoO_(4))_(3):Tm/Yb@Gd_(2)(MoO_(4))_(3):Yb) reach 9,2 and 2,respectively.The considerable enhancement is due to the suppression of surface quenching and energy harvesting via the Yb ions in the outer shell.In addition,the emission color of thin films can be modulated from yellow to blue via tuning the number of Gd_(2)(MoO_(4))_(3):Ho/Yb and Gd_(2)(MoO_(4))_(3):Tm/Yb layers,which provides a feasible strategy to tune the up-conversion emission color.

Tuning electroluminescence performance in Pr-doped piezoelectric bulk ceramics and composites

Alternating current electroluminescence(ACEL)shows great potential in lighting,display and intelligent skin.Herein,the ACEL properties of Pr3þ-doped Ba0$85Ca0$15Ti0$90Zr0$10O3 ceramic and its PDMS-based composite have been investigated.Intense red EL emission was obtained in the ceramic sample whereas blue EL emission of Pr3þwas observed for the first time in the composite counterpart.The red EL emission should be attributed to the impact of hot electrons driven by the large piezoelectric electric field.Owing to the cross-relaxations through the 4f5d levels and Pr-to-metal charge transfer state,the 3 PJ emissions were completely quenched,and thus leading to an enhancement in red emission.However,external E field induced a large local piezoelectric deformation of the ceramic particles embedded in the PDMS matrix,which in turn caused a bending of CB and then a downwards shift of the 4f5d levels from the CB.Hence the cross-relaxations were hindered,and the blue EL emission was observed in the composites.The results would attract attention of functional materials studies and expand our understanding of such facile structure and oxide EL devices to facilitate their use in integral part of flexible device systems.

Recent advances in semitransparent perovskite solar cells

The environmental challenges across the world step up the researcher's interest in different energy resources.Semitransparent perovskite solar cells(STPSCs)could expedite generation of electricity as well as shows reassuring its significance in flexible electronics and building-integrating photovoltaic as so forth in the next decade.It is highly recommended to endorse the relevance of semitransparent solar devices to fulfill the required level of energy even by using the roofs and windows of the buildings.In this review article,we pay more attention to recent developments of ST-PSCs.Herein,a succinct overview of latest research about semitransparent solar cell technologies and ST-PSCs is summarized.Moreover,the strategies to enhance the transparency of solar cells are described utilizing structure,transparent electrodes,perovskite film formation,tandem solar cells,color tuning,and human eye perception.Last but not least is that the serious concerns about stability of ST-PSCs are vividly reviewed.

Adjustable white-light emission from a photo-structured micro-OLED array

White organic light-emitting diodes(OLEDs)are promising candidates for future solid-state lighting applications and backplane illumination in large-area displays.One very specific feature of OLEDs,which is currently gaining momentum,is that they can enable tunable white light emission.This feature is conventionally realized either through the vertical stacking of independent OLEDs emitting different colors or in lateral arrangement of OLEDs.The vertical design is optically difficult to optimize and often results in efficiency compromises between the units.In contrast,the lateral concept introduces severe area losses to dark regions between the subunits,which requires a significantly larger overall device area to achieve equal brightness.Here we demonstrate a color-tunable,two-color OLED device realized by side-by-side alignment of yellow and blue p-i-n OLEDs structured down to 20μm by a simple and up-scalable orthogonal photolithography technique.This layout eliminates the problems of conventional lateral approaches by utilizing all area for light emission.The corresponding emission of the photo-patterned two-unit OLED can be tuned over a wide range from yellow to white to blue colors.The independent control of the different units allows the desired overall spectrum to be set at any given brightness level.Operated as a white light source,the microstructured OLED reaches a luminous efficacy of 13 lm W^(−1) at 1000 cd m^(−2) without an additional light outcoupling enhancement and reaches a color rendering index of 68 when operated near the color point E.Finally,we demonstrate an improved device lifetime by means of size variation of the subunits.

Trivalent Yb/Ho/Ce tri-doped core/shell NaYF4 nanoparticles for tunable upconversion luminescence from green to red

Three types of β-NaYF_4nanoparticles, uncoated core（NaYF_4：Yb/Ho/Ce）, single-layer coated core@shell（NaYF_4：Yb/Ho/Ce@NaYF_4：Yb） and double-layer coated core@shell@shell（NaYF_4：Yb/Ho@NaYF_4：Yb@NaYF_4：Yb） with Ce^（3＋） doped in core, first and second shell, respectively, were synthesized through solvothermal method to investigate the cross-relaxation between Ho^（3＋） and Ce^（3＋） for the tunable upconversion luminescence. By doping Ce^（3＋） into different layers with different doping concentrations, a systematical investigation on the tunable upconversion luminescence from green to red was conducted. The results showed that a remarkable color tuning could be achieved from green to red when increasing the doping concentration of Ce^（3＋） in the same layer of Ho^（3＋）. And if Ce^（3＋） and Ho^（3＋） were separated in different layers, the color tuning would be depressed significantly due to the reduced cross-relaxation between Ho^（3＋） and Ce^（3＋）. Moreover, the UC emission intensity of core@shell and core@shell@shell was enhanced significantly compared with that of unmodified core nanoparticles.