Synthesis of regio- and stereoselective alkoxy-substituted spirobifluorene derivatives for blue light emitting materials

Three new octyloxy substituted spirobifluorenes, 2,7-diphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DPBSBF, 1a), 2,7-dibiphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DBBSBF, 1b) and 2,7-diterphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DTBSBF, 1c) were prepared. All the compounds had been fully characterized by ¹H and ¹³C NMR, UV-Vis, DSC, mass spectrometry and gave satisfactory elemental analyses. They possessed good solubility in common organic solvents and good homogeneous film formation. The optical energy band gap of DBBSBF was 3.27 eV between the HOMO energy level, 5.85 eV, measured by UPS and the LUMO, 2.58 eV, calculated from absorption spectrum. A blue organic light emitting diode (OLED) based on the structure of ITO/TPD (60 nm)/DBBSBF (40 nm)/Alq₃ (20 nm)/LiF (1 nm)/Al (100 nm) showed good performance. The luminance of 3125 cd/m² was observed at a drive voltage of 12.8 V and the colour coordinate in CIE chromaticity was (0.14, 0.12). The external quantum efficiency was obtained to be 2.8% at 100 cd/m².     

Perylenetetracarboxylic diimide derivatives linked with spirobifluorene

A series of perylenetetracarboxylic diimide (PDI) compounds linked with spirobifluorene have been prepared. The orthogonal configuration of the PDI subunits efficiently hindered their molecular aggregation in solution. Energy transfer from a 1,7-diphenoxyl group substituted PDI (PO-PDI) to a 1,7-dipyrrolidinyl group substituted PDI (PY-PDI) occurred with a large efficiency when PO-PDI was selectively excited, despite the orthogonal orientation of the two units. This observation was in direct conflict with predictions derived from the F?rster theory. More interestingly, this efficient energy transfer also occurred in the solid state.     

Synthesis and characterization of stable blue light‐emitting poly(spirobifluorene) derivatives containing alkoxy group

Polymers containing alkoxy‐substituted spirobifluorene have been prepared from nickel(0)‐mediated coupling or palladium‐catalyzed Suzuki coupling. The polymers were characterized using various spectroscopies, such as ¹H‐NMR, FT‐IR, and elemental analysis. The high glass transition temperature and high decomposition temperature suggested that the resulting polymers possessed a high thermal stability. The obtained polymers possessed weight average molecular weight of 4500–33,000 with polydispersity index of 1.1–1.9 and good solubility. The low onsets of the oxidation potential suggested that the polymers containing alkoxy substituted spirobifluorene possessed a good hole injection property. The photoluminescence and electroluminescence of the polymers containing alkoxy substituted spirobifluorene showed stable blue color by suppressing the excimer formation due to intermolecular interaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2316–2324, 2005     

Synthesis and properties of new poly(terfluorene) derivatives containing spirobifluorene and electron transport groups for stable blue electroluminescence

We have synthesized three new blue‐emitting poly(terfluorene) derivatives containing spirobifluorene and electron transport groups (quinoline or oxadiazole). The strategy is to connect the monomers via positions 2 and 2′ of spirobifluorene, which significantly restricts the interchain interaction and effectively adjusts the conjugation length. The incorporation of electron‐deficient units (quinoline or oxadiazole) into the positions 7 and 7′ of spirobifluorene tunes the emission band and reduces the lowest unoccupied molecular orbital energy level. Blue electroluminescence with narrow emission was achieved in the devices of ITO/PEDOT/polymer/Ca/Al. The maximum luminances are in the range of 102–235 cd/m² and the maximum photometric efficiencies are in the range of 0.17–0.21 cd/A. All the polymers show good spectral stability, and are promising for use as stable blue‐emitting or electron‐transport/injection materials in polymeric light‐emitting diodes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4517–4529, 2005     

Synthesis and characterization of deep blue emitters from starburst carbazole/fluorene compounds

A series of well-defined, highly fluorescent starburst compounds with a carbazole core and oligo(2,7-fluorene ethynylene) arms have been synthesized by Sonogashira coupling reaction and fully characterized. These conjugated compounds exhibit good solubility, high thermal stability, and excellent fluorescence quantum yields (up to 0.99). The incorporation of carbazole core interrupted the main-chain conjugation and resulted in blue-shifted absorption and emission. Moreover, deep blue light has been approached from organic light-emitting diodes (OLEDs) adopting these compounds as emitting layer.     

Efficient blue lighting materials based on truxene-cored anthracene derivatives for electroluminescent devices

A new series of anthracene derivatives containing a truxene moiety as the core have been synthesized and characterized. They emit in the blue region with excellent solution fluorescence quantum yields and possess high thermal decomposition temperature (T_d>458 °C). Typical electroluminescence performance was demonstrated by 2-[10-(4-(1-napthenyl)phenyl)anthracene-9-yl]-5,5′,10,10′,15,15′-hexaethyltruxene (NPAT) as the blue lighting material in the OLED with structure of ITO/CFx/NPAT/TPBI or Alq₃/LiF/Al, where TPBI and Alq₃ are 1,3,5-tri(N-phenylbenzimidazol-2-yl)-benzene and tris(8-hydroxyquinolinato)aluminum, respectively. Additionally, the effects of the different thickness of the different electron transporting layers on the device performance were investigated.     

Efficient blue perovskite LEDs from quantum confined structures

正Lead halide perovskites have been leading the optoelectronic field for the last several years, with exceptional progress in photovoltaics and rapid improvement in light emitting diodes(LEDs). LEDs are limited by outcoupling and waveguiding to approximately 20%external quantum efficiency (EQE),and infrared and green perovskite LEDs have already reached this threshold [1–3]. For most applications, however,     

Synthesis of extremely stable blue light emitting poly(spirobifluorene)s with Suzuki polycondensation

[reaction: see text] Full spirobifluorene-based blue light emitting polymers, which exhibited extraordinary thermal and color stability, were prepared with SPC through an AB-type monomer route.     

Novel carbazole/fluorene hybrids: host materials for blue phosphorescent OLEDs

[reaction: see text] A series of carbazole/fluorene (CBZm-Fn) hybrids were effectively synthesized through Friedel-Crafts-type substitution of the carbazole rings. These compounds were thermally and morphologically stable host materials for OLED applications. Efficient blue phosphorescent OLEDs were obtained when employing CBZ1-F2 as the host and FIrpic as the guest.     

寡聚噻吩取代的9,9'-螺二芴的合成和表征

以四种溴化的9,9'-螺二芴为原料,设计合成了一系列新型的寡聚噻吩取代的9,9'－螺二芴。其结构均经1^H,13^CNMR,MS,FT-IR或元素分析确证。通过核磁工振氢谱分析,我们对该类化合物芳环质了的化学位移进行了归属。热重差热分析表明,由于螺二芴的引入,该类化合物具有较高的玻璃化转变温度和明显改善的无定型性。初步的光学性能研究表明,该类化合物寡聚噻吩相比,其荧光效率明显增强,并且随着寡聚噻吩与螺二芴连接位置的不同,其光学性能也有明显差异。     

High-efficiency blue OLEDs based on dendritic dinuclear iridium (III) complexes grafted with fluorene core and blue fluorescence chromospheres

Two novel dendrimer-like blue-emitting dinuclear cyclometalated iridium (III) complexes, namely (DNaTPA)₂DBF(FIrpic)₂ and (DPyTPA)₂DBF(FIrpic)₂, have been successfully synthesized and characterized. In which FIrpic is an iridium (III) bis[(4,6-difluorophenyl)pyridinato-N,C2′]picolate blue-emitting phosphorescent chromophore core, DBF is a 2,7-diphenyl-9H-fluorene bridging core, DNaTPA and DPyTPA are deep blue-emitting fluorescent chromophores composed by rigid high-triplet-energy dendrons of triphenylamine-functionalized naphthalene or pyrene units, and the peripheral dendrons are connected with the ancillary ligand of the emitting core through nonconjugated ether linkage. Their photophysical, thermal, electrochemical, as well as electrophosphorescent properties were primarily studied. Both iridium (III) complexes exhibit high efficient blue emission in solution (38.5% and 19.2%) and a typical FIrpic emission in 1,3-bis(N-carbzolyl)benzene (mCP) matrix (27.0% and 24.1%). Simple bilayer phosphorescent organic light-emitting diodes (PHOLEDs) with a configuration of ITO/PEDOT:PSS/mCP:dopants/TmPyPB/Liq/Al achieved high efficiencies of 12.96 cd/A for current efficiency (CE), 6162 cd/m² for brightness, 6.22% for external quantum efficiency (EQE), and 3.13 lm/W for power efficiency (PE) with Commission International de L'Eclairage (CIE) coordinates of (0.19 ± 0.01, 0.35 ± 0.02) at only 2 wt% blend of (DNaTPA)₂DBF(FIrpic)₂. (DPyTPA)₂DBF(FIrpic)₂-doped devices also reach efficiencies of (9.14 cd/A, 7167 cd/m², 4.41%, 2.61 lm/W) at the same doping concentration. The results demonstrate that the introduction of dendritic blue-emitting fluorescent chromophore grafted into the blue phosphorescent chromosphere core through nonconjugated linkage is an efficient way to achieve high-efficiency sky-blue emission.     

Raman and photoacoustic infrared spectra of fluorene derivatives: Experiment and calculations

Raman and photoacoustic (PA) infrared spectra of fluorene and four derivatives (2,3-benzofluorene, 2-methylfluorene, 2-ethylfluorene and 1,8-dimethylfluorene) were recorded and analyzed in this investigation. Mid- and far-infrared PA spectra were examined from about 2000 to 100 cm⁻¹. The Raman spectra spanned the same wavenumber range. Observed bands in both PA and Raman spectra were compared with DFT (harmonic) and variational (anharmonic) calculations, and with published spectra. The DFT calculations provided single-molecule frequencies, whereas the variational method yielded results for both monomeric and dimeric species. Many previously unknown bands, including numerous features due to combination and overtone transitions, were identified and assigned in this work.     

Spectral locations of low-energy electronic transitions in some fluorene derivatives

The low energy singlet—singlet (S-S) and triplet—triplet (TT) absorption spectra of fluorene and 2-amino fluorene were measured. Also, the spectral locations of low-energy SS and TT intensity maxima of 2-methoxy, 2-hydroxy, 2,7-diamino, and 2-dimethylamino fluorene were recorded.When expressed in wavenumbers (energy) and within measurement accuracy, the following holds for the 2-position substituted fluorene: (a) the red shift caused by a certain substituent is about the same in both (singlet and triplet) manifolds; (b) the energy difference between SS and TT absorption maxima in fluorene as well as in all the substituted compounds is about the same and (c) the spectral red shifts observed in fluorene in the singlet and triplet manifold due to substitution by auxochromic groups can probably be used in fair approximation to estimate anticipated red shifts in other chromophores.For 2,7-diamino fluorene; p-terphenyl, p,p′-diamino, p,p′-diethylamino terphenyl, p-quaterphenyl; p,p′-diamino, p,p−diethylamino quaterphenyl, spectral relations (a) to (c) also hold rather well.     

Efficient deep blue OLEDs with extremely low efficiency roll-off at high brightness based on phenanthroimidazole derivatives

Local emissions located on the PI moiety and anthracene moiety play a key role in alleviating efficiency roll-off at high Brightness in non-doped and doped devices.     

Efficient deep blue OLEDs with extremely low efficiency roll-off at high brightness based on phenanthroimidazole derivatives

Phosphorescent and thermally activated delayed fluorescence(TADF) emitters can break through the spin statistics rules and achieve great success in external quantum efficiency(over 5%).However,maintaining high efficiency at high brightness is a tremendous challenge for applications of organic light emitting diodes.Hence,we reported two phenanthroimidazole derivatives PPI-An-CN and PPI-An-TP and achieved extremely low efficiency roll-off with about 99% of the maximum external quantum efficiency(EQE_(max)) maintained even at a high luminance of 1000 cd/cm2 based non-doped devices.When doping the two materials in CBP(4,4'-bis(N-carbazolyl)-1,1'-biphenyl),the doped devices still exhibited excellent stability at high brightness with CIE_y≈0.07 and low turn-on voltage of only 2.8 V.The state-ofthe-art low efficiency roll-off makes the new materials attractive for potential applications.It is the first time that the Fragment Contribution Analysis method has been used to analyze the excited state properties of the molecules in the field of OLEDs,which helps us understand the mechanism more intuitively and deeply.     

Symmetric anionic polymethine dyes derived from fluorene and its derivatives with electron-acceptor substituents: synthesis and spectral properties

Novel anionic polymethine dyes were synthesized from 2,7-bis(phenoxysulfonyl)-, 2,7-dinitro-, and 2,4,5,7-tetranitrofluorenes. The reasons for the complicated shape of their absorption spectra were analyzed: the formation of contact ion pairs, associates, and conformational isomers and electronic effects of substituents. The quantum chemical calculations by the Pariser??Parr??Pople method and nonempirical DFT and TDDFT methods in the B3LYP/6-31G(d,p) basis set revealed that the orbitals of the nitro groups, unlike the orbitals of the SO₂OPh groups, are efficiently conjugated with the common chromophore system inducing additional electron transitions.