Glass-forming carbazolylidene-containing hydrazones as hole-transporting materials

The synthesis, optical, thermal and photoelectrical properties of carbazole- and phenothiazine-containing hydrazones are reported. The ionization potentials of the films of the hydrazones, measured by the electron photoemission technique, range from 5.20 to 5.60 eV. Room temperature time-of-flight hole mobilities in the solid solutions of carbazole phenothiazine and carbazole carbazole hydrazones in bisphenol-Z polycarbonate exceeded 10^?5 cm²/(V s) at high applied electric fields.     

Phenotiazinyl-based hydrazones as new hole-transporting materials for electrophotographic photoreceptors

Various phenothiazinyl-based hydrazones including cross-linkable derivatives have been synthesized by the multi-step synthetic route. Full characterization of their structure is presented. The materials were examined by various techniques including differential scanning calorimetry, UV spectrometry, electron photoemission and time of flight techniques. The electron photoemission spectra of the layers showed the ionisation potentials of 5.3–5.4 eV. Room temperature hole drift mobility of some derivatives molecularly dispersed in bisphenol Z polycarbonate approached 5 × 10⁻⁶ cm²/Vs at high electric fields.     

3,6-Di(diphenylamino)-9-alkylcarbazole-based hole-transporting hydrazones

The synthesis of a series of new glass-forming hydrazones containing carbazole and diphenylamine moieties is reported. The thermal, optical and photoelectrical properties of mono-, di- and tetra-substituted compounds are compared. The glass transition temperatures of the newly synthesized hydrazones range from 75 to 145 °C. The ionization potentials of the films of hydrazones, measured by the electron photoemission technique, range from 4.74 to 5.15 eV. Hole-drift mobilities of the solid solutions of hydrazones in bisphenol Z polycarbonate (50 wt.%) are in the range of 6.3 × 10⁻⁶ to 1.1 × 10⁻⁵ cm²/Vs at electric field of 6.4 × 10⁵ V/cm as characterized by the time-of-flight method.     

Indole and phenylenediamine based enamines as amorphous hole-transporting materials

New aromatic enamines were synthesized by condensation of the commercially available N-phenyl-p-phenylenediamine, indole or 2-methylindole with 2,2-diphenylacetaldehyde or 2-phenylpropionaldehyde. Twin derivatives of the 2-methylindole-based enamine were prepared. The materials were examined by various techniques including differential scanning calorimetry, UV spectrometry, electron photoemission and time of flight techniques. The electron photoemission spectra of layers of the amorphous materials showed the ionization potentials of 5.26–5.6 eV. Hole drift mobilities in the layers range from 4.7 × 10^?6 to 10^?4 cm²/(V s). Some of the materials were tested as hole-transporting layers in light emitting diodes with Alq₃ as the electroluminescent/electron transport layer. The device containing indole-based enamine exhibited the best overall performance with a turn-on voltage of 3 V, maximum brightness of about 3500 cd/m² and luminance efficiency of 1.62 lm/W.     

Cross-linkable aromatic amines as materials for insoluble hole-transporting layers in light-emitting devices

A series of cross-linkable aromatic amines has been synthesized by the multi-step synthetic rout. Full characterization of their structure by ¹H NMR-, IR- and mass spectrometry is presented. The synthesized materials were examined by various techniques including differential scanning calorimetry, thermogravimetry, UV and electron photoemission spectrometry. The electron photoemission spectra of the layers showed their ionisation potentials of 5.1–5.2 eV. One of the derivatives was used for the preparation of insoluble hole-transporting layers by photoinduced polymerization. The layers obtained were tested in multilayer light-emitting diodes. The device-containing hole-transporting layer of PEDOT/cross-linked network exhibited the best overall performance with a turn-on voltage of 5 V, a maximum photometric efficiency of 2.8 cd/A and a maximum brightness of ca. 5600 cd/m².     

Phenoxazine and N-phenyl-1-naphtylamine-based enamines as hole-transporting glass-forming materials

New aromatic enamines were synthesized by condensation of the commercially available phenoxazine and N-phenyl-1-naphtylamine with 2,2-diphenylacetaldehyde or 2-phenylpropionaldehyde. The materials were examined by various techniques including differential scanning calorimetry, UV and fluorescence spectrometry, electron photoemission and time of flight techniques. The electron photoemission spectra of the layers of the amorphous materials showed the ionization potentials of 5.42–5.61 eV. Hole drift mobilities in the layers of 33–50% solid solutions of the derivatives in bisphenol Z polycarbonate range from 10⁻⁵ to 3.4 × 10⁻⁴ cm²/V s at high electric fields.     

Solution-processable dendric triphenylamine nonamers as hole-transporting and hole-injection materials for organic light-emitting devices

We demonstrated two solution-processable triphenylamine dendric nonamers: the N-atom-centered nonamer (TPA9-1) and the phenyl-centered nonamer (TPA9-2). The materials were found to have high glass transition temperature (T_g) up to almost 200 °C. The fractional difference of the central units of the molecular structures caused different adaptability due to the different ionization potentials (I_p). TPA9-1 (N-atom-centered), whose I_p was smaller than that of TPA9-2 (phenyl-centered), was suitable as hole-injection layer material, and TPA9-2 was suitable as hole-transporting layer material. Computational chemistry provides a ready explanation for the I_p difference between the two materials.     

Well defined carbazole-based hole-transporting amorphous molecular materials

Monodisperse carbazole-based oligomers have been synthesized via CN bonds formation by the modified Ullmann reaction. The full characterization of their structure is presented. These derivatives are highly thermally stable amorphous compounds with glass transition temperatures of 167–171 °C and thermal decomposition temperatures of ca. 400 °C. Amorphous films of the materials were fabricated and their hole-transporting properties were tested in a light emitting device with Alq₃ as an electroluminescent and electron-transporting material.     

Highly efficient organic light-emitting diodes using novel hole-transporting materials

A new class of tetraminobiphenyl derivatives, which contains a 3,3′,5,5′-tetraminobiphenyl core, has been synthesized and examined as a hole-transporting material for organic light-emitting diodes. We fabricated the organic light-emitting diode (OLED) cells with tetraminobiphenyl derivatives as hole-injecting layer, hole-transporting layer and hole-injecting and transporting layer for green device with tris(8-quinolinolato)aluminum (Alq₃) doped with 1% of Coumarin 545T (C545T) as green emitting layer. Tetraminobiphenyls were found to be useful as a novel hole-transporting material. The electroluminescent device with the 3,3′,5,5′-tetrakis(p-tolyldiamino)biphenyl (TTAB) as a hole-transporting layer was more efficient than that with the analogous triarylamine, N,N′-di(naphthalene-1-yl)-N,N′-diphenyl benzidine (NPB). The external luminous efficiency of the device IV having TTAB as one hole-injecting and transporting layer can reach 14.55 cd/A, which is higher than the standard device I (11.66 cd/A) using two layers, a hole-injecting layer and a hole-transporting layer.     

Diphenylamino-substituted derivatives of 9-phenylcarbazole as glass-forming hole-transporting materials for solid state dye sensitized solar cells

The synthesis and properties of glass-forming diphenylamino-substituted derivatives of 9-phenylcarbazole with methoxy groups in the different position of diphenylamino moieties are reported. A comparative study on their thermal, optical, photoelectrical and electrochemical properties is presented. The synthesized compounds exhibit high thermal stability with 5% weight loss temperatures ranging from 344 to 475 °C. The derivatives absorb electromagnetic irradiation in the range of 225–425 nm with the band gaps of 2.94–3.08 eV. The ionization energies of the synthesized compounds range from 5.04 to 5.56 eV. The lowest ionization energies and band gaps are observed for compounds containing para methoxy-substituted phenyl rings of diphenylamino moieties and for disubstituted carbazole derivatives. Charge-transporting properties of the selected compounds were tested by time-of-flight technique. Hole drift mobilities in the amorphous layers of the materials reach 10⁻³ cm²/V s at high electric fields. The derivatives were tested as hole transport materials in solid-state dye sensitized solar cells and showed conversion efficiency up to 0.54%.     

Improved performance of organic light-emitting diodes using advanced hole-transporting materials

A new class of aryl amine derivatives, which contains phenylnaphthyldiamine core, has been synthesized and examined as a hole-transporting material (HTM) for organic light-emitting diodes (OLEDs). These phenylnaphthyldiamine derivatives possess high radical cation stabilities and high morphologic stabilities relative to their biphenyldiamine analogs. Theoretical experiments and OLED device fabrication were carried out to study their better hole-transporting properties. The electroluminescent devices with the phenylnaphthyldiamine derivatives HTM 2–4 as the hole-transporting layer were more efficient than that with the biphenyldiamine HTM 1.     

Luminance materials containing carbazole and triphenylamine exhibiting high hole-transporting properties

Two novel 2-substitutd-8-hydroxyquinoline derivatives were designed and synthesized. Their luminance properties and carrier transporting abilities were studied when integrated in four different organic light-emitting device structures. The four devices are structured as following—device A: indium tin oxide glass substrate (ITO)/2-TNATA/NPB/(2-[2-(9-ethyl-9H-carbazol-2-yl)-vinyl]-quinolato zinc (1) and 2-[2-(4-diphenylamino-phenyl)-vinyl]-quinolato zinc (2))/Alq₃/LiF/aluminum (Al); device B: ITO/2-TNATA/NPB/1 or 2/LiF/Al; device C: ITO/2-TNATA/1 or 2/Alq₃/LiF/Al; device D: ITO/2-TNATA/1 or 2/Alq₃/LiF/Al. In the device A, the maximum brightness of compound 1 is 5857 cd m⁻² at 11 V with the luminance efficiency 1.84 cd A⁻¹. For 2 it is 6047 cd m⁻² at 10 V with an efficiency of 2.22 cd A⁻¹. In the device B, the maximum brightness of 1 is 745 cd m⁻² at 11 V and efficiency is 0.32 cd A⁻¹. These values are 1748 cd m⁻² at 10 V and 0.42 cd A⁻¹ for 2, respectively. In the device C, the maximum brightness of 1 and 2 are 8729 and 5838 cd m⁻² at 10 V, respectively, with an efficiency of 1.99 and 1.71 cd A⁻¹. In the device D, the maximum brightness and efficiency of 1 are 8512 cd m⁻² at 13 V and 3.10 cd A⁻¹, and they are 9818 cd m⁻² at 13 V and 0.42 cd A⁻¹, for 2. Our results also show that both 1 and 2 are good bipolar and bifunctional molecules with high hole-transporting and luminance properties.     

Phenyl-, carbazolyl- and fluorenyl-substituted derivatives of indolo[3,2-b]carbazole as hole-transporting glass forming materials

A series of new derivatives of indolo[3,2-b]carbazole containing phenyl, fluorenyl and carbazolyl substituents at the nitrogen atoms were synthesized by Ullmann coupling of 6-pentyl-5,11-dihydroindolo[3,2-b]carbazole with the different aryl halogenides. The optical, photophysical, photoelectrical and thermal properties of the materials obtained were studied. All the synthesized compounds can be transformed into the amorphous phase with the glass transition temperatures ranging from 0 to 154 °C. The ionization potentials of the newly synthesized derivatives of indolo[3,2-b]carbazole are in the range of 5.22–5.48 eV. The lowest energy absorption edges and the lowest ionization potentials were observed for carbazolyl-substituted derivatives. Charge transport properties of the synthesized materials were estimated by the time-of-flight technique. The highest hole drift mobilities were observed for the fluorenyl-substituted derivative. For the molecular glass of 5,11-bis(9,9-dibutyl-9H-fluoren-2-yl)-6-pentyl-5,11-dihydroindolo[3,2-b]carbazole they exceed 10^?3 cm²/V s at an electric field of 3.6 × 10⁵ V/cm.     

New hole-transporting dihydrazones

Synthesis and photoelectric properties of new glass-forming diphenylsulfone dihydrazones with the glass transition temperatures ranging from 22 to 123 °C are reported. The ionization potentials of the films of diphenylsulfone dihydrazones measured by the electron photoemission technique range from 5.00 to 5.33 eV. The hole-drift mobilities in the amorphous films of the diphenylsulfone dihydrazones bearing alkyl substituents doped in bisphenol Z polycarbonate (PC-Z) approach 10⁻⁵ cm²/(Vs) at high-applied electric fields as characterized by the time-of-flight method.     

Effect of electron- and hole-transporting materials on the performance of FIrpic-doped PVK phosphorescent devices

PVK-based phosphorescent FIrpic-doped devices have been fabricated and the effect of carrier transporting materials on the device performance has been investigated. We have fabricated the single-layer and double-layer devices to investigate the role of electron- and hole-transporting materials both when they are mixed in the single- and separated from the emissive layer. We have studied NPB as a hole-transporting material, OXD-7 and PBD as electron-transporting materials. Even though PBD had been well known to be unsuitable as an electron-transporting material for FIrpic-doped PVK devices, it was found in this study that the separate utilization of PBD from PVK:FIrpic layer instead of mixing it with the emissive layer could enhance the device performance significantly. Nevertheless, the OXD-7 was found not only superior to PBD as the electron-transporting material for FIrpic-doped PVK devices but also suitable as an electron-transporting material for the single-layer devices.     

Recent progress in organic hole-transporting materials with 4-anisylamino-based end caps for efficient perovskite solar cells

Perovskite solar cells(PVSCs) have emerged as a promising photovoltaic technology and have attracted wide research interest due to their outstanding photovoltaic performance, low cost, and the ability to fabricate largearea devices. An impressive certified power conversion efficiency(PCE) of 25.2% has been achieved, demonstrating the excellent potential of PVSCs for future applications. Hole-transporting materials play a key role in improving the device performance of PVSCs by facilitating the extraction of photogenerated holes and their transport from the perovskite layer to the anode. This review provides a brief introduction to PVSCs and summarizes the recent progress in small molecule hole-transporting materials(SM-HTMs) bearing various cores and different4-anisylamino-based end caps. We classify the end caps into N,N-di-4-anisylamino(DAA), 4-(N,N-di-4-anisylamino)benzo(DAB), and N3, N6(or N2, N7)-bis(di-4-anisylamino)-9 H-carbazole(3,6-DAC or 2,7-DAC) groups.We also review the core type, end cap position and number,how these affect the overall properties of the SM-HTMs,and the resultant PVSC device performances. Finally, the challenges and perspectives for the future development of SM-HTMs are presented.     

New amorphous hole-transporting molecular materials: 1,1,1-Tris(4-(4-diarylaminobenzoyloxy)phenyl)ethane

Efficient new amorphous hole-transporting molecular materials (AHTMs) with high glass transition temperatures (T_g>117 °C). have been developed. AHTMs were easily prepared by condensation of 1,1,1-Tris(4-hydroxyphenyl)ethane (1) and triphenylamine derivatives using a condensing agent dicyclohexylcarbodiimide (DCC). The organic light-emitting device (OLED) prepared by using spin-cast films from the AHTMs onto the ITO-coated glass substrate in conjunction with Alq/Mg:Ag as a electron-transporting layer and a metal cathode, respectively, showed the maximum luminescence of 14,000 cd/m² at 12 V.     

钨基面向等离子体材料的研究进展

综述了国内外广泛研究的W-La2O3和W-TiC合金的制备工艺、力学性能和辐照性能的研究进展。结果表明:向钨基体中加入La2O3弥散相,虽然能够显著改善钨的强度和韧性,但使钨的抗辐照性能降低,氢泡密度和氢滞留量明显增加;当采用TiC纳米颗粒作为弥散相,经过热等静压烧结和塑性加工后,钨合金的抗弯强度达到4.4 GPa,再结晶温度高于2 473K,韧脆转变温度(DBTT)比纯钨的低100 K;TiC的加入能够显著提高钨的抗辐照性能,与纯钨相比,氚滞留量减小,没有明显的辐照硬化,材料表面没有裂纹和剥落。     

Synthesis of new hole-transporting molecular glass with pendant carbazolyl moieties

The synthesis and properties of amorphous hole-transporting 4,4′-bis[11-carbazol-9-yl)-6,8,10-tri(carbazol-9-methyl)-3-hydroxy-5,7,9-trioxa-1-thia]thiobisbenzene with two end and six pendant carbazolyl moieties, separated from the main chain by CH₂ spacers, is reported. It was prepared by a multistep synthesis route from 1,6-di(carbazol-9-yl)-5-(carbazol-9-methyl)-4-oxa-2-hexanol glycidyl ether. Glass transition temperatures of intermediate and final products established by differential scanning calorimetry are reported. The hole drift mobility, measured by the time of flight technique, in this well defined molecular glass depends little on the strength of the electric field and exceeds 10⁻⁵ cm² V⁻¹ s⁻¹. The ionization potentials measured by electron photoemission method, light absorption and fluorescence spectra are closed to those reported for the other organic photoconductors containing electronically isolated carbazole moieties.