Co-reporter:Xiangfei Kong;Liting Xia;Haifeng Zhang;Shengping Dai;Caili Yu;Zheng Liu;Linping Mu;Guixia Wang
RSC Advances (2011-Present) 2017 vol. 7(Issue 28) pp:17030-17037
Publication Date(Web):2017/03/17
DOI:10.1039/C7RA01320E
Four novel mesogenic dyads consisting of a hexa(alkoxy)triphenylene donor that was linked to a perylene tetracarboxylic esters acceptor by the bridges (O–(CH2)2–O), (O–(CH2)6–O), (O–(CH2)10–O) and (O–(CH2)12–O), had been synthesized. Their structures were characterized by 13C and 1H nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and elemental analysis (EA). The experimental results of cyclic voltammetry and UV/Vis showed the aliphatic linkage of the donor–acceptor dyads preserved the genuine electrochemical behaviors and light absorption properties of the donor and acceptor units, and the energy level difference between the HOMO of the donor and the LUMO of the acceptor is about 1.94 eV. The differential scanning calorimetry (DSC) traces and polarizing optical microscopy (POM) textures confirmed that all dyads had mesophase. When excited at 443 nm, fluorescence quenching process of the acceptor unit was ascribed to a intramolecular ground-state charge transfer from the donor to it. And the fluorescence quenching varying with the bridge lengths were understood by Dexter-type energy transfer theory. These behaviors of photoinduced intramolecular charge transfer and forming columnar liquid crystal phase made these dyads candidates of new active materials in organic solar cells.
Co-reporter:Huan Zhao, Zhiqun He, Min Xu, Chunjun Liang and Sandeep Kumar
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 12) pp:8554-8560
Publication Date(Web):23 Feb 2016
DOI:10.1039/C6CP00031B
An electron transporting anthraquinone derivative demonstrated a stable large-scale homeotropic alignment on an open substrate surface, which substantially improved its charge carrier mobility. The electron mobility (μE) increased by two orders of magnitude from 3.2 × 10−4 cm2 V−1 s−1 for the film without alignment to 1.2 × 10−2 cm2 V−1 s−1 for the homeotropically aligned film. A distinct enhancement in the UV absorption spectra of the films around the short wavelength range was observed to be associated with the molecular alignments. These alignments are less sensitive to the substrate under test. The anchoring force of the columnar stacks appears to be related to the nature of the material associated with the strong interaction between the molecules and substrate interface.
Co-reporter:Ying Peng, Zhiqun He, Han Li, Chunjun Liang
Polymer 2016 Volume 98() pp:61-69
Publication Date(Web):19 August 2016
DOI:10.1016/j.polymer.2016.06.002
•High and low temperature crystallites of same crystalline forms can be developed in P3HT.•High temperature crystallite is highly ordered melting at relative high-temperature.•Low temperature crystallite has a low degree order melting at a variable and lower temperature.•Isothermal crystallization can increase the high temperature crystallite population.•Enhanced temperature and/or prolonged crystallization time promoted phase separation.In this work, multiple transitions from isothermally crystallized poly(3-hexylthiophene) (P3HT) and their correlations to the structure were investigated. It was discovered that high and low temperature crystallites of varying degree orders can be formed in P3HT matrices during the isothermal crystallization. The high temperature crystallite was highly ordered crystalline form having melting temperature around 230 °C; while the low temperature crystallite was quasicrystalline of limited ordered having a varying endothermic transition temperature depending on crystallization conditions. The population of high temperature crystallites can be manipulated by the variation of isothermal crystallization conditions. The small angle X-ray scattering revealed a progressive phase separation at appropriate crystallization temperature and/or prolonged crystallization times.
Co-reporter:Yong Zhao, Chunjun Liang, Huimin Zhang, Dan Li, Ding Tian, Guobao Li, Xiping Jing, Wenguan Zhang, Weikang Xiao, Qian Liu, Fujun Zhang and Zhiqun He
Energy & Environmental Science 2015 vol. 8(Issue 4) pp:1256-1260
Publication Date(Web):12 Feb 2015
DOI:10.1039/C4EE04064C
It is proved that a large amount of mobile ions exist in organic–inorganic halide perovskites. The accumulated ions at the interface change the band bending of the semiconductor, leading to polarity-switchable photovoltaic devices. The interface charge significantly influences the function and performance of perovskite devices. The discovery of the interface charge has important implications for current–voltage hysteresis in perovskite solar cells.
Co-reporter:Huimin Zhang;Hong Lin;Chunjun Liang;Hong Liu;Jingjing Liang;Yong Zhao;Wenguan Zhang;Mengjie Sun;Weikang Xiao;Han Li;Stefano Polizzi;Dan Li;Fujun Zhang;Wallace C. H. Choy
Advanced Functional Materials 2015 Volume 25( Issue 46) pp:7226-7232
Publication Date(Web):
DOI:10.1002/adfm.201502962
While perovskite light-emitting diodes typically made with high work function anodes and low work function cathodes have recently gained intense interests. Perovskite light-emitting devices with two high work function electrodes with interesting features are demonstrated here. Firstly, electroluminescence can be easily obtained from both forward and reverse biases. Secondly, the results of impedance spectroscopy indicate that the ionic conductivity in the iodide perovskite (CH3NH3PbI3) is large with a value of ≈10−8 S cm−1. Thirdly, the shift of the emission spectrum in the mixed halide perovskite (CH3NH3PbI3−xBrx) light-emitting devices indicates that I− ions are mobile in the perovskites. Fourthly, this work shows that the accumulated ions at the interfaces result in a large capacitance (≈100 μF cm−2). The above results conclusively prove that the organic–inorganic halide perovskites are solid electrolytes with mixed ionic and electronic conductivity and the light-emitting device is a light-emitting electrochemical cell. The work also suggests that the organic–inorganic halide perovskites are potential energy-storage materials, which may be applicable in the field of solid-state supercapacitors and batteries.
Co-reporter:Weikang Xiao, Zhiqun He, Sonia Remiro-Buenamañana, Rebecca J. Turner, Min Xu, Xiao Yang, Xiping Jing, and Andrew N. Cammidge
Organic Letters 2015 Volume 17(Issue 13) pp:3286-3289
Publication Date(Web):June 19, 2015
DOI:10.1021/acs.orglett.5b01444
β-Amino triphenylenes can be accessed via palladium catalyzed amination of the corresponding triflate using benzophenone imine. Transformation of amine 6 to benzoyl amide 18 is also straightforward, and its wide mesophase range demonstrates that the new linkage supports columnar liquid crystal formation. Amine 6 also undergoes clean aerobic oxidation to give a new twinned structure linked through an electron-poor pyrazine ring. The new discotic liquid crystal motif contains donor and acceptor fragments and is more oval in shape rather than disk-like. It forms a wide range columnar mesophase. Absorption spectra are strong and broad; emission is also broad and occurs with a Stokes shift of ca. 0.7 eV, indicative of charge-transfer character.
Co-reporter:Huimin Zhang, Chunjun Liang, Yong Zhao, Mengjie Sun, Hong Liu, Jingjing Liang, Dan Li, Fujun Zhang and Zhiqun He
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 15) pp:9613-9618
Publication Date(Web):05 Mar 2015
DOI:10.1039/C5CP00416K
The accumulation of mobile ions causes space charge at interfaces in perovskite solar cells. There is a slow dynamic process of ion redistribution when the bias is changed. The interface charge affects band bending and thus the photocurrent of the solar cells. Consequently the dynamic process of the interface charge governs the current–voltage hysteresis. Very low interface charge density leads to hysteresis-free devices.
Co-reporter:Weikang Xiao, Zhiqun He, Min Xu, Nan Wu, Xiangfei Kong, Xiping Jing
Tetrahedron Letters 2015 Volume 56(Issue 5) pp:700-705
Publication Date(Web):28 January 2015
DOI:10.1016/j.tetlet.2014.12.070
This work reveals a novel reaction route deviated from a Scholl coupling reaction with an interrogation into the mechanism. A catalytic function of FeCl3 in the presence of protons plays a key role in the new reaction. It was discovered that by increasing the quantity of reagent FeCl3 is able to shift the reaction product from a symmetrically hexa-substituted coupling one to a mono-hydrolysed coupling product. The discovery offers a chance to explore and understand the reaction mechanism further. The new reaction enables a convenient one-step synthesis of mono-hydroxy-penta-alkoxytriphenylene, a key discotic liquid crystal intermediate for organic electronic materials, from a simple 1,2-dialkoxybenzenes reactant at a yield up to 65%.
Co-reporter:Xiangfei Kong, Zhiqun He, Hemant Gopee, Xiping Jing, Andrew N. Cammidge
Tetrahedron Letters 2011 Volume 52(Issue 1) pp:77-79
Publication Date(Web):5 January 2011
DOI:10.1016/j.tetlet.2010.10.152
Monohydroxypentaalkoxytriphenylenes are important intermediates for elaboration into complex covalently linked discotic liquid crystal assemblies. An improved, simple synthetic protocol is described that gives rapid access to these precursors in a single step.Monohydroxypentaalkoxytriphenylenes MHTn are important and versatile intermediates for synthesis of twinned and linked discotic structures. We report an optimized protocol for their convenient preparation and isolation using a ferric chloride mediated mixed cyclisation strategy.
Co-reporter:Juanjuan Li, Zhiqun He, Hemant Gopee and Andrew N Cammidge
Organic Letters 2010 Volume 12(Issue 3) pp:472-475
Publication Date(Web):January 5, 2010
DOI:10.1021/ol902637z
Novel triphenylene dimers linked by a central crown ether core have been synthesized and characterized. The crown ether is most conveniently formed as a final step to permit purification and isolation of ion-free material, and extension of the protocol permits synthesis of triad structures linked though a 27-crown-9 macrocycle. The latter compounds present a new discotic motif that supports mesophase formation.
Co-reporter:Wenguan Zhang, Zhiqun He, Linping Mu, Ye Zou, Yongsheng Wang, Shengmin Zhao
Dyes and Pigments 2010 Volume 85(Issue 3) pp:86-92
Publication Date(Web):May 2010
DOI:10.1016/j.dyepig.2009.10.008
A diarylamine, 2-(phenylamino)-9,9-diethylfluorene and three red fluorescent dyes based on arylamino fumaronitrile derivatives, bis(4-(N-(1-naphthyl)phenylamino)-phenyl)fumaronitrile (1-NPAFN, 5a), bis(4-(N-(2-naphthyl)phenylamino)phenyl)-fumaronitrile (2-NPAFN, 5b) and bis(4-(N-(9,9-diethyl-2-fluorenyl)phenylamino)-phenyl)fumaronitrile (EFPAFN, 5c), were prepared. The red dyes showed strong red photoluminescence upon excitation which centered at around 635, 650, 658 nm for 1-NPAFN, 2-NPAFN and EFPAFN in solid film respectively. Fluorescence concentration quenching of red dyes was suppressed. Thermal stability and energy levels were also measured. Multilayer non-doped electroluminescent devices were fabricated using the red dyes (5b, 5c) as red emitters. Device performance kept relatively constant at a wide current density level in the range of 20–150 mA/cm2.
Co-reporter:Wenguan Zhang, Yongsheng Wang, Zhiqun He, Linping Mu, Ye Zou, Chunjun Liang, Shengmin Zhao
Synthetic Metals 2010 Volume 160(5–6) pp:354-360
Publication Date(Web):March 2010
DOI:10.1016/j.synthmet.2009.11.004
A novel cyclometalated ligand 2-(9,9-diethylfluoren-2-yl)-5-trifluoromethyl-pyridine (fl-5CF3-py), and its complexes bis[2-(9,9-diethylfluoren-2-yl)-5-trifluoromethyl-pyridinto-C3, N]iridium (acetylacetonate) (fl-5CF3-py)2Ir(acac) (5) and bis[2-(9,9-diethylfluoren-2-yl)-5-trifluoromethylpyridinto-C3, N] iridium (2-picolinic acid) (fl-5CF3-py)2Ir(pic) (6) were synthesized, respectively. Trifluoromethyl group and 2-picolinic acid were incorporated into iridium ligands to tune luminescent color. Emission spectra of 5 and 6 in THF solutions were 589 and 572 nm. Decomposition temperatures (Td) of 5 and 6 were 326 and 360 °C. Multilayer electrophosphorescent devices were fabricated using 5 and 6 as emitter dopants with electroluminescent spectra maximized at around 585 and 571 nm, respectively. The relatively high efficiencies of the devices and their slow rate of decay against increases in current densities indicated that (fl-5CF3-py)2Ir(acac) or (fl-5CF3-py)2Ir(pic) was a promising emitter for practical device applications.
Co-reporter:Junjie Wang, Zhiqun He, Yingning Zhang, Huan Zhao, Chunxiu Zhang, Xiangfei Kong, Linping Mu, Chunjun Liang
Thin Solid Films 2010 Volume 518(Issue 8) pp:1973-1979
Publication Date(Web):1 February 2010
DOI:10.1016/j.tsf.2009.07.057
An interesting discotic triphenylene derivative, 2,7-biscarbethoxy-3,6,10,11-tetrapentyloxytriphenylene, can be homeotropically aligned on a large scale as a film on single substrates, i.e. the film with one side on the substrate and the other side freestanding. The alignment is achieved in a controlled condition close to a thermodynamic equilibrium state in a liquid crystal phase when interactions at the substrate surface are limited. Phase changing properties of this material are also a key factor in the alignment processes. The aligned structures are observed with an optical microscope. Within a single domain a hexagonal lattice of a d-spacing 16.3 Å is confirmed by X-ray diffraction measurement.
Co-reporter:Linping Mu ;Xiangfei Kong;Guanbao Hui;Min Xu;Chunjun Liang Dr.;Xiping Jing Dr.;Andrzej Danel Dr.;Ewa Kulig Dr.
ChemPhysChem 2010 Volume 11( Issue 12) pp:2623-2629
Publication Date(Web):
DOI:10.1002/cphc.201000152
Abstract
Pyrazolo[3,4-b]quinoline derivatives are reported to be highly efficient organic fluorescent materials suitable for applications in light-emitting devices. Although their fluorescence remains stable in organic solvents or in aqueous solution even in the presence of H2O, halide salts (LiCl), alkali (NaOH) and weak acid (acetic acid), it suffers an efficient quenching process in the presence of protic acid (HCl) in aqueous or ethanolic solution. This quenching process is accompanied by a change in the UV spectrum, but it is reversible and can be fully recovered. Both steady-state and transient fluorescence spectra of 1-phenyl-3,4-dimethyl-1H-pyrazolo-[3,4-b]quinoline (PAQ5) during quenching are measured and analyzed. It is found that a combined dynamic and static quenching mechanism is responsible for the quenching processes. The ground-state proton-transfer complex [PAQ5⋅⋅⋅H+] is responsible for static quenching. It changes linearly with proton concentration [H+] with a bimolecular association constant KS=1.95 M−1 controlled by the equilibrium dissociation of HCl in ethanol. A dynamic quenching constant KD=22.4 M−1 is obtained by fitting to the Stern–Volmer equation, with a bimolecular dynamic quenching rate constant kd=1.03×109 s−1 M−1 under ambient conditions. A change in electron distribution is simulated and explains the experiment results.
Co-reporter:WenGuan Zhang;GuanBao Hui;LinPing Mu
Science China Chemistry 2009 Volume 52( Issue 7) pp:952-960
Publication Date(Web):2009 July
DOI:10.1007/s11426-009-0077-0
A fluorescent organic triarylamine with a symmetric structure, 2,7-bis(N-α-naphthyl-phenylamino)-9,9-diethylfluorene (NPAEF) was synthesized using two methods, modified Ullmann coupling and modified palladium-catalyzed amination. An activated copper and a combination of Pd(OAc)2/P(t-Bu)3 and Pd(dba)2/P(t-Bu)3 were selected as catalysts to improve yields of reactions. These synthetic procedures were also successfully applied to an asymmetric 2-dimesitylboron-7-(N-phenyl-α-naphthylamino)-9,9-diethylfluorene (BNPEF). Photoluminescent emission peaks in solid film and in diluted solution of NPAEF were both observed at 461 nm, while the main emission peaks of BNPEF appeared at 422 nm in hexane, and at 480 nm in methanol. The double emission peaks of BNPEF in hexane reflected fine structure in the vibrational state. With an increasing polarity of solvent, the main PL emission peaks were red-shifted and vibrational fine structure disappeared. Additionally, energy levels of NPAEF were investigated and an electroluminescence (EL) device of ITO/PVK:NPAEF/Al was fabricated, which showed a turn-on voltage of 9 V and peaked at 462 nm. The EL spectrum was in good agreement with PL spectrum, which indicated that they were from the same emitting center in the device.
Co-reporter:Chunxiu Zhang, Zhiqun He, Junjie Wang, Yongsheng Wang, Shi Ye
Journal of Molecular Liquids 2008 Volume 138(1–3) pp:93-99
Publication Date(Web):15 February 2008
DOI:10.1016/j.molliq.2007.09.003
A novel liquid crystalline material which consists of both discotic and calamitic units to form a star structure bearing a triphenylene as centre core and three cyanobiphenyl tails has been synthesized. Phase behaviour of the material was investigated using polarised optical microscopy, thermal analysis and X-ray diffraction. The heterogeneous tetramer showed multi-mesophases that can be kinetically controlled. When the pure tetramer was heated up and cooled down at 10 °C min− 1 directly, it showed only a crystalline phase and no mesophase. The annealing sample showed smectic mesophase and the quenched sample showed nematic phase, columnar phase can be induced by TNF in the binary system containing the tetramer and TNF.
Co-reporter:Huan Zhao, Zhiqun He, Min Xu, Chunjun Liang and Sandeep Kumar
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 12) pp:NaN8560-8560
Publication Date(Web):2016/02/23
DOI:10.1039/C6CP00031B
An electron transporting anthraquinone derivative demonstrated a stable large-scale homeotropic alignment on an open substrate surface, which substantially improved its charge carrier mobility. The electron mobility (μE) increased by two orders of magnitude from 3.2 × 10−4 cm2 V−1 s−1 for the film without alignment to 1.2 × 10−2 cm2 V−1 s−1 for the homeotropically aligned film. A distinct enhancement in the UV absorption spectra of the films around the short wavelength range was observed to be associated with the molecular alignments. These alignments are less sensitive to the substrate under test. The anchoring force of the columnar stacks appears to be related to the nature of the material associated with the strong interaction between the molecules and substrate interface.
Co-reporter:Huimin Zhang, Chunjun Liang, Yong Zhao, Mengjie Sun, Hong Liu, Jingjing Liang, Dan Li, Fujun Zhang and Zhiqun He
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 15) pp:NaN9618-9618
Publication Date(Web):2015/03/05
DOI:10.1039/C5CP00416K
The accumulation of mobile ions causes space charge at interfaces in perovskite solar cells. There is a slow dynamic process of ion redistribution when the bias is changed. The interface charge affects band bending and thus the photocurrent of the solar cells. Consequently the dynamic process of the interface charge governs the current–voltage hysteresis. Very low interface charge density leads to hysteresis-free devices.
