Preparation of organic/inorganic hybrid nanocomposites by ultraviolet irradiation and their packaging applications for organic optoelectronic devices

By ultraviolet (UV)-assisted synthetic procedure, we have successfully prepared several UV curable organic/inorganic hybrid nanocomposites with excellent gas barrier capabilities, moderate hardness, and good adhesive strength. The experimental results reveal that the physical properties of nanocomposites depend on their chemical structures. Therefore, introduction of silicone and polyurethane (PU) into the Acrylics backbone dramatically raises the adhesive strength as well as refractive index and lowers the gas penetration. Furthermore, we have also applied lab-made nanocomposite g for the encapsulation of organic optoelectronic devices such as OLEDs, flexible OLEDs, and organic solar cells. With the package of lab-made nanocomposite g, the organic optoelectronic devices effectively resist the entry of moisture and oxygen in the air, extending the lifetimes.     

Microwave‐assisted facile synthesis of liquid crystalline non‐symmetrical hexaalkoxytriphenylenes containing a branched chain and their characterization

Two novel series of liquid crystalline non‐symmetrical hexaalkoxytriphenylenes containing a branched alkyl chain have been prepared using microwave dielectric heating. Series 1 contains 2‐ethyl hexyloxy group as the branched chain whereas series 2 contains 3,7‐dimethyl octyloxy as the branched chain along with five normal alkoxy chains. The number of carbon atoms varies from four to eight in the normal alkoxy chains. Mesophase behaviour of the compounds has been characterized by polarizing optical microscopy, differential scanning calorimetry and mesophase structure has been characterized by X‐ray diffractometry. All the compounds show enantiotropic mesophase transitions with columnar hexagonal structure. In series 1 ( 4a – e ) the mesophase range and transition temperatures of all the compounds are lowered as compared to the parent compounds whereas in series 2 ( 5a – e ) the transition temperatures of all the compounds are lowered, mesophase range for lower members are decreased, however, higher members show more mesophase stability. Both melting and clearing temperatures of series 2 ( 5a – e ) show strong odd–even effect. The intercolumnar distance increases as expected for compounds of both the series with increase in alkyl chain length with some degree of interdigitation of the alkyl chains. The intercolumnar distances for the compounds of the series 2 are slightly higher than the compounds of the series 1 . Compound 4c displays homeotropic alignment without using any special technique for alignment of the columnar phase or application of any external force. Copyright © 2007 John Wiley & Sons, Ltd.     

梯度掺杂体异质结对有机太阳能电池光电转换效率的影响

基于传统的体异质结有机太阳能电池结构, 对结构中的混合层改用梯度掺杂的方法, 在AM1.5, 100 mW/cm²光照下, 使得器件的短路电流由原来的7.72 mA/cm²提高到了9.18 mA/cm², 相应的光电转换效率提高了25%. 器件性能的提升归因于梯度掺杂体系的引入使得体异质结混合层中同一材料分子之间形成了较好的连续网络结构, 降低了器件的串联电阻, 提高了电极对载流子的收集效率, 从而提高了器件的光电转换效率. 关键词： 有机太阳能电池 体异质结 梯度掺杂     

Microwave‐assisted facile synthesis of propargylamine library by robust nitro functionalized cross‐linked polystyrene resin supported Cu NPs

In the present investigation, we study catalytic activity of copper nanoparticles stabilized onto a nitro functionalized polystyrene resin (Cu NPs@ Nitro‐Resin). The size of stabilized copper nanoparticles was found between 3 and 9 nm. This work reports a cost‐effective and sustainable protocol for the synthesis of propargylamines. Herein, we have developed microwave‐assisted synthesis of propargylamine from 3 components coupling of aldehyde, alkynes, and amines (A³ coupling) in truly heterogeneous catalytic system. Reaction parameters, such as solvent, catalyst concentration reaction time, and recyclability, were investigated, and reaction conditions were optimized. The present method has advantages such as environmentally benign, ease to handle, short reaction time (≈25 min), excellent yields (98%), low E‐factor (0.15), and high atom economy (94%).     

Concentration quenching effect of organic light‐emitting devices using DCM1‐doped tetraphenylgermole

We examine the concentration quenching of a 4‐(dicyanomethylene)2‐methyl‐6‐(p‐dimethylaminostyryl)‐4H‐pyran (DCM1)‐doped 1,1‐bis(2‐phenylethynyl)‐2,3,4,5‐tetraphenylgermole (HPAG)‐based light‐emitting diode. Originally, HPAG emits in the ~500‐nm (green) region, which can be converted to a red‐emission material by using DCM1 doping. As the DCM1 concentration increased from 1 to 10 wt%, the electroluminescence peak positions are red‐shifted from 604 to 644 nm, respectively. Increasing doping density not only shows the red‐shift but also shows decreasing luminance efficiency. Förster energy transfer between the HPAG host material and the DCM1 guest material is responsible for the strong red‐emission behavior. The calculated Förster radius (4.0 nm) for excellent Förster energy transfer characteristics with increasing doping concentration of DCM1 is consistent with experimental results. The maximum luminance efficiency was 6.64 cd/A at 11.0 mA/cm². The HPAG germole compound shows excellent red‐emission host–guest system properties for red organic light‐emitting device applications. Copyright © 2011 John Wiley & Sons, Ltd.     

New template based nanoelectrode arrays for organic/inorganic photovoltaic applications

In this Letter, we report on a new nanofabrication technology to yield highly arrayed nanoelectrodes for organic–inorganic solar cells that promise new levels of performance and efficiency. This technology efficiently controls the effective area of highly arrayed nanoelectrodes and allows for the maximum incorporation of organic materials within the voids. Particularly the 3D parameters such as thickness, spacing, and height of the nanostructures are controlled non‐lithographically by atomic layer deposition technology.

     

Efficient synthesis and tailoring of magnetic and dielectric properties of Pb‐free perovskite‐like ABX3 metal‐organic frameworks

Perovskite‐like metal‐organic frameworks (MOFs) are hybrid materials of high interest for their potential in information storage technology, as Pb‐free substitutes for the widely used lead zirconate titanate (PZT) family of multiferroics. We report here a new, microwave‐assisted method of synthesis for perovskite‐like MOFs, which exploits the advantages of rapid and volumetric heating by microwaves in order to achieve synthesis within minutes, compared to days required by previously reported methods. The preliminary results demonstrate a broad control over the size and morphology of the products, by minor changes in the reaction conditions. An investigation of the effects of size and morphology on the magnetic and dielectric properties is presented here.

     

Density functional theory analysis of a mixed‐ligand iridium compound for multi‐color organic light‐emitting diodes

Electronic states and their energies are calculated for a mixed‐ligand Ir(III) compound, (5‐chloro‐8‐hydroxyquinoline) bis(2‐phenylpyridyl) iridium (called IrQ(ppy)₂‐5Cl) using time‐dependent density functional theory (TDDFT) calculations and are compared with the experimental result. A good agreement is obtained between the calculated and measured absorption spectra. The d‐π_Q* molecular orbital transition gives the lowest‐energy triplet state absorption band. Its energy is estimated as 1.84 eV (671 nm), which is close to the absorption band position of 1.86 eV (666 nm) observed for IrQ(ppy)₂‐5Cl doped in 4,4′‐N,N′‐dicarbazole‐biphenyl (CBP) host and of 1.88 eV (660 nm) observed for IrQ(ppy)₂‐5Cl doped in polystyrene (PS). The second triplet state absorption band is caused by d‐π_ppy transition. Its position is calculated as 2.51 eV (494 nm). The dipole moment is estimated as 3.45 D, which is lower than the dipole moment of fac‐Ir(ppy)₃. This is understood by a reduced charge transfer between Ir(III) and quinoline ligand. Copyright © 2008 John Wiley & Sons, Ltd.     

Barrier characteristics of biopolymer-based organic/inorganic Au/CTS/n-InP hybrid junctions

Thin film of biopolymeric compound chitosan (CTS) has been surfaced on moderately doped n-InP substrate as an interfacial layer by means of spin coating for the electronic modification of Au/n-InP structure. Electrical characterization of Au/CTS/n-InP hybrid junction has been performed by I–V and C–V measurements at room temperature. An effective barrier height (BH) value of 0.678 eV and an ideality factor of n = 1.665 have been obtained for the hybrid junction. The CTS interfacial layer has been found to reduce the reverse bias leakage current of the junction by about three orders of magnitude and enhance the BH by about 0.213 eV. Furthermore, the BH value of the hybrid junction has been obtained as 0.693 eV by C–V measurement. Good performance of the device could be ascribed to the passivation effect of the CTS interfacial layer between Au and n-InP. The BH values of 0.678 and 0.693 eV for the hybrid junction have been significantly higher than that of the conventional Au/n-InP junction (~0.465 eV). The results indicated that biopolymeric thin interfacial CTS layer might lead to the modification of the potential barrier for metal/n-InP junctions. Moreover, band gap of the CTS layer has been determined as 4.60 eV via UV–vis spectroscopy.     

High‐stability organic red‐light photodetector for narrowband applications

Red‐light photodetectors without filters are in urgent need for narrowband applications such as full‐color imaging and multi‐output visible light communication (VLC). However, their development is hindered by the lack of small‐band‐gap and narrowband response materials. Without wavelength filters, a new type of photodetector with a simple single‐layer architecture is developed, based on a stable small‐band‐gap squarylium dye and characterized by a detectivity peak at 680 nm and full width at half maximum of 80 nm. The device, which exhibits high stability in air and humid conditions, shows a significantly low dark current of ∼2 nA·cm⁻² at −2 V and high specific detectivity of 3.2 × 10¹² Jones. The response current ratio of the device to red, green, and blue lights with a luminous flux amplitude ratio of 3:6:1 (standard ratio for white light) is 100:12:1.1. These properties indicate that the squarylium dye red‐light photodetectors are promising for VLC and other narrowband optoelectronic applications.

     

Electronic properties of 2D and 3D hybrid organic/inorganic perovskites for optoelectronic and photovoltaic applications

We herein investigate theoretically both 2D and 3D Hybrid Organic/inorganic perovskite crystal structures based on density functional theory (DFT) calculations and symmetry analyses. Our findings reveal the universal features of the electronic band structure for the class of lead-halide hybrids (R-NH \(_{3})_{n}\hbox {PbX}_{m}\) , where \((\mathrm{{n}}, \mathrm{{m}})=(2,4)\) and (1,3) respectively for 2D and 3D structures. Among those, the large spin-orbit coupling acting on the conduction band is shown to play a major role on the band gap of these materials. Moreover, this approach can easily be generalized to related layered and 3D hybrids, thus providing a clear-sighted inside in their electronic and optical properties.     

多环类苝四甲酸二酐插入层对ZnO纳米棒和聚合物复合太阳电池性能的影响

以ZnO纳米棒和聚[2-甲氧基-5-(2-乙基-己氧基)-1,4-苯撑乙烯撑](MEH-PPV)的复合体系作为光敏层制备了太阳电池.为了增大电池的光吸收,在ZnO纳米棒与MEH-PPV之间插入了有机n型小分子多环类苝四甲酸二酐(PTCDA),制备了不同厚度的PTCDA、结构为ITO/ZnO纳米棒/PTCDA/MEH-PPV/Au的太阳电池.实验发现,插入PTCDA后,电池在可见光区的吸收增强,光生激子数量增大,光电流密度增大.当蒸镀的PTCDA厚度为40 nm时,薄膜的粗糙度适中,表面形貌较为平滑,器件性 关键词： 有机太阳电池 ZnO纳米棒 聚合物     

Ultraviolet-assisted synthesis of encapsulating adhesives and their application for lifetime improvement of organic light emitting diodes

The lifetimes of organic light emitting diodes (OLEDs) have been successfully enhanced with the modulation of LiF thickness and the utilization of encapsulating adhesives, which have been successfully and quickly synthesized with UV irradiation. Experimental results demonstrate that LiF and lab-made encapsulating adhesives can block the invasion of moisture as well as oxygen in the atmosphere into the OLEDs so that the lifetimes of devices with their encapsulation are 18-folds longer than those without encapsulation.     

Functional organic single crystals for solid‐state laser applications

In the article by Hong‐Hua Fang et al. (doi: http://dx.doi.org/10.1002/lpor.201300222 ), published in Laser Photonics Rev. 8, 687–715 (2014), the names of two authors in references were wrongly spelt and citations in the text were missing. This erratum is published to correct this.     

Functional organic single crystals for solid‐state laser applications

Because of long‐range order and high chemical purity, organic crystals have exhibit unique properties and attracted a lot of interest for application in solid‐state lasers. As optical gain materials, they exhibit high stimulated emission cross section and broad tunable wavelength emission as similar to their amorphous counterpart; moreover, high purity and high order give them superior properties such as low scattering trap densities, high thermal stability, as well as highly polarized emission. As electronic materials, they are potentially able to support high current densities, thus making it possible to realize current driven lasers. This paper mainly describes recent research progress in organic semiconductor laser crystals. The building molecules, crystal growth methods, as well as their stimulated emission characteristics related with crystal structures are introduced; in addition, the current state‐of‐the‐art in the field of crystal laser devices is reviewed. Furthermore, recent advances of crystal lasers at the nanoscale and single crystal light‐emitting transistors (LETs) are presented. Finally, an outlook and personal view is provided on the further developments of laser crystals and their applications.     

聚对二甲苯薄膜的制备及其在有机电致发光二极管中的应用研究

使用自制的分子束源制备了聚对二甲苯（Parylene N,PPXN）薄膜。通过对该分子束源的设计和不断优化,PPXN薄膜可以在室温、10-3 Pa的较低反应压强下以0.01 nm/s~0.02 nm/s的速率沉积聚合。用红外透射光谱和原子力显微镜测量了PPXN薄膜的成分和表面形貌。结果表明,所制备的薄膜成分为PPXN,薄膜呈波浪状、无尖刺的表面形貌。准确控制的PPXN薄膜在有机电致发光二极管中用作缓冲层,对载流子的注入和传输进行调控,有效地改善了器件内部的载流子平衡。最优化结构的器件较未插入PPXN缓冲层的器件,电流效率提高80%以上。     

Fabrication and characterization of dual-band organic/inorganic photodetector for optoelectronic applications

In this work, the optoelectronic performance of organic/inorganic heterojunction photodiode based on alpha-sexithiophene (α-6T/n-Si) is introduced. A thin film of α-6T was deposited on the n-type silicon substrate by a thermal evaporation technique. The topographical properties of the α-6T thin film grown on the n-Si substrate were investigated using a field emission scanning electron microscope (FESEM) technique. A network of nanocrystalline needles over the film surface was observed which give rise to an improvement in the electric charge transport. The optical properties of the prepared thin film were investigated using a spectrophotometric technique. The high absorption of α-6T in UV and visible region suggested the ability of this architecture for UV and visible light detection. The I-V characteristics of the fabricated photodiode were investigated in dark and under different illumination intensities and different wavelengths. The present architecture showed a good response to halogen lamb light, where the estimated values of rising and falling time at 160 mW/cm² were about 400 ms and 450 ms, respectively. The results show the possibility of using Au/α-6T/n-Si/Al structure as a photodetector for a wide range of the solar spectrum (UV–Visible).     

Fabrication of ZnO and its enhancement of charge injection and transport in hybrid organic/inorganic light emitting devices

ZnO nanocrystals were synthesized by hydrolysis in methanol. X-ray diffraction and photoluminescence spectra confirm that good crystallized ZnO nanoparticles were formed. Utilizing those ZnO nanoparticles and poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV), light emitting devices with indium tin oxide (ITO)/poly(3,4-oxyethyleneoxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS)/ZnO:MDMO-PPV/Al and ITO/PEDOT:PSS/MDMO-PPV/Al structures were fabricated. Electroluminescence (EL) spectra reveal that EL yield of hybrid MDMO-PPV and ZnO nanocrystals devices increased greatly as compared with pristine MDMO-PPV devices. The current-voltage characteristics indicate that addition of ZnO nanocrystals can facilitate electrical injection and charge transport. The decreased energy barrier to electron injection is responsible for the increased efficiency of electron injection.     

Light manipulation in organic light‐emitting devices by integrating micro/nano patterns

The demonstration of high efficiency and color tunability has brought organic light‐emitting devices (OLEDs) into the lighting and display market. High efficiency is one of the key issues for their commercial applications, for which much effort has been devoted to developing novel materials and device structures. It is well known that around 80% of the generated photons are trapped in OLED structure, so that there is still the greatest scope for significant improvements in its efficiency. This has driven the research towards the integration of micro/nano patterns into device structures that benefit from their abilities in manipulating the generation and propagation of photons. Micro/nano patterns with random or periodic morphologies have demonstrated their effect on the outcoupling of the trapped photons within the device. Moreover, the emitting properties other than the light extraction could be manipulated by introducing the micro/nano patterns. This article reviews the recent progresses in improving the light extraction and manipulating the emission properties of the OLEDs through the introduction of the micro/nano patterns by various fabrication strategies. The light manipulation of the micro/nano patterns in organic photovoltaics is briefly discussed considering its similar working principle and fabrication strategies to that of the OLEDs.