Bending-stability Interfacial Layer as Dual Electron Transport Layer for Flexible Organic Photovoltaics

The flexibility of organic photovoltaics (OPVs) has attracted worldwide attention in recent years.To realize the bending-stability of OPVs,it is necessary to put forward the bending-stability of interracial layer.A novel bendable composite is explored and successfully applied as an electron transport layer (ETL) for fully-flexible OPVs.We incorporated poly(vinylpyrrolidone)(PVP) into conjugated electrolytes (CPE) to composite a bendable ETL for high-performance OPVs devices.Fortunately,the devices based on PVP-modified CPE exhibited better device performances and more excellent mechanical properties of bendability.The fullerene-free OPVs based on PM6:IT-4F with CPE@PVP as ETLs yield the best power conversion efficiency (PCE) of 13.42％.Moreover,a satisfying efficiency of 12.59％ has been obtained for the fully-flexible OPVs.As far as we know,this is one of the highest PCE for fully-flexible OPV based PM6:IT-4F system.More importantly,the flexible OPVs devices can retain more than 80％ of its initial efficiency after 5000 bending cycles.Furthermore,among various curvature radii,the mechanical properties of the device based on CPE@PVP are superior to those of the device based on bare CPE as ETL.These findings indicate that the functional flexibility of CPE as a cathode interfacial layer is an effective strategy to fabricate high-performance flexible devices in the near future.     

四(8-羟基喹啉)硼锂作为电子注入层的高效有机发光二极管

采用四(8-羟基喹啉)硼锂(LiBq4)代替LiF 作为电子注入材料, 以金属铝作为阴极, 制备了有机电致发光器件. 器件采用N,N'-(α-萘基)-N,N'-苯基联苯二胺(NPB)作为空穴传输层, 三(8-羟基喹啉)铝(Alq3)作为电子传输层和发光层. 采用LiBq4作为电子注入层, 实验结果表明, 器件的亮度、电流效率和起亮电压等性能均有改善, 超过了采用LiF作为电子注入层的器件.器件性能的提升可以用电子注入增强和电荷平衡来解释.     

Synthesis and optoelectronic properties of amino-functionalized carbazole-based conjugated polymers

A series of alcohol soluble amino-functionalized carbazole-based copolymers were synthesized via Suzuki coupling reaction.The pendent amino groups endow them high solubility in polar solvents,as well as efficient electron injection capability from high work-function metals.The relationships between the photophysical and electrochemical properties and the polymer backbone structure were systematically investigated.These alcohol-soluble carbazole-based copolymers were used as cathode interlayers between the high work-function metal Al cathode and P-PPV emissive layer in polymer light-emitting diodes with device structure of ITO/PEDOT:PSS/P-PPV/interlayer/Al.The resulting devices exhibited improved performance due to the better electron injection/transporting ability of the designed copolymers from Al cathode to the light-emitting layer.     

胺基功能化咔唑共轭聚合物的合成及其光电性能研究

发展了新型含有胺基的支化烷基修饰的咔唑单元,并且与芴、咔唑、苯等单元通过Suzuki偶联反应共聚得到不同主链结构的水/醇溶共轭聚合物界面修饰材料,研究了主链结构的变化对材料光物理、电化学性能的影响.所有聚合物均被用作阴极界面材料应用于器件结构为ITO/PEDOT：PSS/P-PPV/界面层/Al的聚合物发光二极管中.在相同器件制备条件下,系统比较了不同主链结构的界面修饰材料在器件中的性能,并研究了性能差异的原因.器件研究结果表明,在高功函数金属Al阴极的聚合物发光二极管中,含胺基功能化咔唑单元的水/醇溶共轭聚合物材料由于界面偶极的形成,均表现出很好的电子注入/传输性能,与之对应的器件性能得到大幅提升.     

水/醇溶共轭聚合物界面材料及其在光电器件中的应用

相对于传统的无机半导体器件,以有机半导体(特别是聚合物半导体)材料为基础的有机光电器件,可采用与传统印刷技术(例如喷墨打印、卷对卷印刷等)相结合的溶液加工方式制备低成本、大面积、柔性光电器件,因而成为广泛关注的焦点,并得到了快速发展.实现溶液加工的高效有机光电器件的一个关键问题是界面问题——如何避免溶液加工时有机层间的互溶以及如何实现可印刷稳定金属电极的高效电子注入等.水/醇溶性共轭聚合物的迅速发展为解决溶液加工多层有机光电器件所面临的界面问题提供了有效手段.研究发现,水/醇溶共轭聚合物不但可以有效避免溶液加工多层器件中的界面互溶,而且还可与高功函数的稳定金属发生界面偶极相互作用而增强其电子注入,从而解决了高功函数稳定金属电子注入的难题,为实现全溶液加工的高效印刷有机光电器件提供了可行的方案.本文介绍了近年来本课题组在水/醇溶共轭聚合物阴极界面材料及器件应用方面的研究进展,并对水/醇溶共轭聚合物阴极界面材料在聚合物发光二极管和聚合物太阳电池中的工作机理进行了探讨.     

Conjugated zwitterionic polyelectrolyte as the charge injection layer for high-performance polymer light-emitting diodes

A new zwitterionic conjugated polyelectrolyte without free counterions has been used as an electron injection material in polymer light-emitting diodes. Both the efficiency and maximum brightness were considerably improved in comparison with standard Ca cathode devices. The devices showed very fast response times, indicating that the improved performance is, in addition to hole blocking, due to dipoles at the cathode interface, which facilitate electron injection.     

Control of interchain contacts, solid-state fluorescence quantum yield, and charge transport of cationic conjugated polyelectrolytes by choice of anion

Simple procedures are provided for exchanging charge-compensating ions in conjugated polyelectrolytes by progressive dilution of the original species and for determining the degree of ion exchange by using X-ray photoelectron spectroscopy. By using these methods, the bromide ions in poly[(9,9-bis(6'-N,N,N-trimethylammoniumbromide)hexyl)fluorene-co-alt-4,7-(2,1,3-benzothiadiazole)]were exchanged with BF4-, CF3SO3-, PF6-, BPh4-, and B(3,5-(CF3)2C6H3)4- (BArF4-). Absorption, photoluminescence (PL), and PL quantum yields (Phi) were measured in different solvents and in solid films cast from methanol. Examination of the resulting trends, together with the spectral bandshapes in different solvents, suggests that increasing the counteranion (CA) size decreases interchain contacts and aggregation and leads to a substantial increase of Phi in the bulk. Size analysis of polymers containing Br- and BArF4- in water by dynamic light scattering techniques indicates suppression of aggregation by BArF4-. Nanoscale current-voltage measurements of films using conducting atomic force microscopy show that hole mobilities and, more significantly, charge injection barriers are CA dependent. These results show that it is possible to significantly modify the optoelectronic properties of conjugated polyelectrolytes by choosing different counterions. A parent conjugated backbone can thus be fine-tuned for specific applications.     

Alkali metal salts doped pluronic block polymers as electron injection/transport layers for high performance polymer light-emitting diodes

A series of alkali metal salts doped pluronic block copolymer F127 were used as electron injection/transport layers (ETLs) for polymer light-emitting diodes with poly[2-(4-(3′,7′-dimethyloctyloxy)-phenyl)-p-phenylenevinylene] (P-PPV) as the emission layer. It was found that the electron transport capability of F127 can be effectively enhanced by doping with alkali metal salts. By using Li2CO3 (15%) doped F127 as ETL, the resulting device exhibited improved performance with a maximum luminous efficiency (LE) of 13.59 cd/A and a maximum brightness of 5529 cd/m2, while the device with undoped F127 as ETL only showed a maximum LE of 8.78 cd/A and a maximum brightness of 2952 cd/m2. The effects of the doping concentration, cations and anions of the alkali metal salts on the performance of the resulting devices were investigated. It was found that most of the alkali metal salt dopants can dramatically enhance the electron transport capability of F127 ETL and the performance of the resulting devices was greatly improved.     

Creating a pseudometallic state of K+ by intercalation into 18-crown-6 grafted on polyfluorene as electron injection layer for high performance PLEDs with oxygen- and moisture-stable Al cathode

Polymer light-emitting diodes (PLEDs) suffer from inadequate lifetimes because of the use of environmentally sensitive metals as the cathodes. We present the use of water/methanol-soluble polyfluorene grafted with 18-crown-6 chelating to K(+) as the electron-injection layer (EIL) for deep-blue-emission PLEDs, allowing the use of environmentally stable Al as the cathode since electron donation from the 18-crown-6 can reduce K(+) to a stable "pseudometallic state", enabling it to act as an intermediate step for electron injection. Furthermore, when poly(ethylene oxide) was blended into the EIL to provide hole blocking (HB), the device exhibited the highest performance reported to date for a deep-blue-emission PLED based on a conjugated polymer as the emitting layer, with a brightness of 54,800 cd/m(2) and an external quantum efficiency of 5.42%. The use of such an EI-HB layer opens a broad avenue leading toward industrialization of PLEDs.     

TiO_2 nanoparticle-based electron transport layer with improved wettability for efficient planar-heterojunction perovskite solar cell

The electron transport layer(ETL) plays an important role in planar heterojunction perovskite solar cell(PSCs),by affecting the light-harvesting, electron injection and transportation processes, and especially the crystallization of perovskite absorber. In this work, we utilized a commercial TKD-TiO_2 nanoparticle with a small diameter of 6 nm for the first time to prepare a compact ETL by spin coating. The packing of small-size particles endowed TKD-TiO_2 ETL an appropriate surface-wettability, which is beneficial to the crystallization of perovskite deposited via solution-processed method. The uniform and high-transmittance TKD-TiO_2 films were successfully incorporated into PSCs as ETLs. Further careful optimization of ETL thickness gave birth to a highest power conversion efficiency of 11.0%, which was much higher than that of PSC using an ETL with the same thickness made by spray pyrolysis. This TKD-TiO_2 provided a universal solar material suitable for the further large-scale production of PSCs. The excellent morphology and the convenient preparation method of TKD-TiO_2 film gave it an extensive application in photovoltaic devices.     

In-situ fabrication of dual porous titanium dioxide films as anode for carbon cathode based perovskite solar cell

We develop a dual porous(DP) TiO_2 film for the electron transporting layer(ETL) in carbon cathode based perovskite solar cells(C-PSCs). The DP TiO_2 film was synthesized via a facile PS-templated method with the thickness being controlled by the spin-coating speed. It was found that there is an optimum DP TiO_2 film thickness for achieving an effective ETL, a suitable perovskite/TiO_2 interface, an efficient light harvester and thus a high performance C-PSC. In particular, such a DP TiO_2 film can act as a scaffold for complete-filling of the pores with perovskite and for forming high-quality perovskite crystals that are seamlessly interfaced with Ti_O2 to enhance interfacial charge injection. Leveraging the unique advantages of DPTiO2 ETL, together with a dense-packed and pinhole-free TiO_2 compact layer, PCE of the C-PSCs has reached 9.81% with good stability.     

Synthesis, characterization, and complexation of tetraarylborates with aromatic cations and their use in chemical sensors

Five aromatic borate anions, namely tetrakis(4-phenoxyphenyl)borate (1), tetrakis(biphenyl)borate (2), tetrakis(2-naphthyl)borate (3), tetrakis(4-phenylphenol)borate (4), and tetrakis(4-phenoxy)borate (5), have been prepared and tested as ion-recognition sites in chemical sensors for certain aromatic cations and metal ions. To gain further insight into the complexation of the cations, some complexes have been prepared and structurally characterized. The complexation behavior of 1 and 2 towards N-methylpyridinium (6), 1-ethyl-4-(methoxycarbonyl)pyridinium (7), tropylium (8), imidazolium (9), and 1-methylimidazolium (10) cations has been studied, and the stability constants of the complexes of 1 with cations 6 and 8 have been measured to compare them with the values for the previously studied complexes of tetraphenylborate. The structures of the borate anions and their complexes have been characterized by NMR and mass spectrometric methods. X-ray crystal structures have been determined for potassium tetrakis(4-phenoxyphenyl)borate (K(+)1), N-methylpyridinium tetrakis(4-phenoxyphenyl)borate (61), 1-ethyl-4-(methoxycarbonyl)pyridinium tetrakis(4-phenoxyphenyl)borate (71), tropylium tetrakis(4-phenoxyphenyl)borate (81), and imidazolium tetrakis(biphenyl)borate (92). The results show that borate derivatives are potential candidates for a completely new family of charged carriers for use in cation-selective electrodes.     

An Ionic Molecular Glass as Electron Injection Layer for Efficient Polymer Light‐Emitting Diode

An ionic molecular glass based on a dendronized monoammonium salt has been facilely synthesized and utilized as an interfacial electron‐injection layer in a light‐emitting diode (LED). The characterization of a yellow‐green LED that involves an Al cathode and a thin layer of the new compound spin cast from a methanol solution has shown device performances comparable to those obtained with a Ba/Al cathode. Photovoltaic measurements under white light irradiation reveal that a thin layer of the new compound can significantly increase the built‐in potential and thus facilitate electron injection from an Al cathode. Furthermore, it is interesting to observe that the new ionic salt could undergo reorganization on the emissive conjugated polymer layer, which leads to the formation of nearly uniform nanoaggregates.

     

Transforming Ionene Polymers into Efficient Cathode Interlayers with Pendent Fullerenes

A new and highly efficient cathode interlayer material for organic photovoltaics (OPVs) was produced by integrating C₆₀ fullerene monomers into ionene polymers. The power of these novel “C₆₀‐ionenes” for interface modification enables the use of numerous high work‐function metals (e.g., silver, copper, and gold) as the cathode in efficient OPV devices. C₆₀‐ionene boosted power conversion efficiencies (PCEs) of solar cells, fabricated with silver cathodes, from 2.79 % to 10.51 % for devices with a fullerene acceptor in the active layer, and from 3.89 % to 11.04 % for devices with a non‐fullerene acceptor in the active layer, demonstrating the versatility of this interfacial layer. The introduction of fullerene moieties dramatically improved the conductivity of ionene polymers, affording devices with high efficiency by reducing charge accumulation at the cathode/active layer interface. The power of C₆₀‐ionene to improve electron injection and extraction between metal electrodes and organic semiconductors highlights its promise to overcome energy barriers at the hard‐soft materials interface to the benefit of organic electronics.     

Remarkable effects of counter ions on scandium ion-promoted electron transfer reactions

Scandium ion-promoted electron transfer reactions of p-benzoquinone are remarkably accelerated when tetrakis(pentafluorophenyl)borate anion is used instead of trifluoromethanesulfonate anion as the counter anion of scandium ion. Only a catalytic amount of scandium borate salt (Sc[B(C6F5)4]3) accelerates significantly the Diels-Alder reaction of 9,10-dimethylanthracene with p-benzoquinone, which proceeds via Sc(3+)-promoted electron transfer from the anthracene to p-benzoquinone.     

Organic Light Emitting Diodes with Lithium Contained Alq3 as Electron Injection Layer

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｏｒｇａｎｉｃｌｉｇｈｔｅｍｉｔｔｉｎｇｄｉｏｄｅ(ＯＬＥＤ) ,ｓｏｍｅｍｅｔａｌｓｗｉｔｈｌｏｗｗｏｒｋｆｕｎｃｔｉｏｎ ,ｓｕｃｈａｓａｌｌｏｙｏｆｍａｇ ｎｅｓｉｕｍａｎｄｓｉｌｖｅｒ(Ｍｇ∶Ａｇ) [1] ａｎｄａｌｕｍｉｎｉｕｍ[2 ] ,ａｒｅｕｓｅｄａｓｔｈｅｅｌｅｃｔｒｏｎｉｎｊｅｃｔｉｏｎｃａｔｈｏｄｅｓ .ＩｎＭｇ∶Ａｇａｌ ｌｏｙｓｉｌｖｅｒｉｓｕｓｅｄｔｏｐｒｏｔｅｃｔｍａｇｎｅｓｉｕｍｆｒｏｍｔｈｅｒｅａｃ ｔｉｏｎｏｆｍａｇｎｅｓｉｕｍｗｉｔｈｏｘｙｇｅｎａｎｄ…     

Synthesis and optical and electroluminescent properties of novel conjugated polyelectrolytes and their neutral precursors derived from fluorene and benzoselenadiazole

Novel copolymers derived from amino‐functionalized fluorene‐ and selenium‐containing heterocycles [2,1,3‐benzoselenadiazole (BSeD)] were synthesized by the palladium‐catalyzed Suzuki coupling method. Their quaternized salt polyelectrolytes of corresponding compositions were obtained by a postpolymerization treatment. The resulting copolymers were soluble in polar solvents. An efficient energy transfer due to exciton trapping on the BSeD sites was observed. Devices from such copolymers emitted orange‐red light peaked at 560–610 nm. All the polymers showed good device performance with high‐work‐function metal Al as a cathode without the use of an additional electron‐injection layer and are promising candidates for polymer light‐emitting diode applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2521–2532, 2006     

Applications of Ytterbium in organic light-emitting devices as high performance and transparent electrodes

Potential applications of Ytterbium (Yb) in cathode system for organic optoelectronic/electronic devices were explored in NPB/Alq₃ based bi-layer organic light-emitting devices (OLEDs). When a thin (14.5 nm) Yb layer capped with a thicker (200 nm) Ag layer was used as the cathode, the OLEDs show enhanced electron injection over those using the standard Mg:Ag cathode. Performance of the OLEDs with the Yb/Ag cathode is comparable to that using LiF/Al cathode. Interestingly, we also found that Yb can also be used to prepare a highly transparent cathode by co-evaporating Yb and Ag to form a Yb:Ag alloy electrode. Surface-emitting (or top emission) and transparent (emission from both surfaces) OLEDs with low turn-on voltage (3.75 V) and high efficiency were prepared with the Yb:Ag electrode.     

电子传输材料1,3,4-哐恶二唑衍生物和1,2,4-三唑衍生物的DFT研究

The simplest organic light-emitting-diode (OLED) device is a two layer device of: ITO/HTL/ETL/Mg: Ag, in which HTL or ETL can act as light emitter. The mobilities of charge are important in optimizing the performance of OLED devices, as high mobilities reduce the resistance of the device leading to greater power efficiency. The electron-transport in the organic solid can be viewed as an electron hopping process. By means of DFT (B3LYP) methods, the structures of two kinds of electron-transport materials in neutral, cationic and anionic states were optimized. The results suggest that the process of electronic transmission of 2,5-diphenyl-1,3,4-oxadiazole is mainly the N→O transferences, the process of electronic transmission of 3,4,5-triphenyl-1,2,4-triazole is mainly the N(double linkage)→N(single linkage) transferences and the transition from the triazole ring to the benzene ring connected with the N atom. The third position of the benzene ring was substituted by the electron acceptor groups, the electronic transmission performance was enhanced, while it was substituted by the electron donor groups, the electronic transmission performance was reduced.     

Solid contact PVC membrane electrodes based on neutral or charged carriers for the selective reading of anionic sulfamethoxazole and their application to the analysis of aquaculture water

Sulfamethoxazole (SMX) is among the antibiotics employed in aquaculture for prophylactic and therapeutic reasons. Environmental and food spread may be prevented by controlling its levels in several stages of fish farming. The present work proposes for this purpose new SMX selective electrodes for the potentiometric determination of this sulphonamide in water. The selective membranes were made of polyvinyl chloride (PVC) with tetraphenylporphyrin manganese (III) chloride or cyclodextrin-based acting as ionophores. 2-nitrophenyl octyl ether was employed as plasticizer and tetraoctylammonium, dimethyldioctadecylammonium bromide or potassium tetrakis (4-chlorophenyl) borate was used as anionic or cationic additive. The best analytical performance was reported for ISEs of tetraphenylporphyrin manganese (III) chloride with 50% mol of potassium tetrakis (4-chlorophenyl) borate compared to ionophore. Nersntian behaviour was observed from 4.0?×?10^?5 to 1.0?×?10^?2?mol/L (10.0 to 2500?µg/mL), and the limit of detection was 1.2?×?10^?5?mol/L (3.0?µg/mL). In general, the electrodes displayed steady potentials in the pH range of 6 to 9. Emf equilibrium was reached before 15?s in all concentration levels. The electrodes revealed good discriminating ability in environmental samples. The analytical application to contaminated waters showed recoveries from 96 to 106%.