基于在聚合物中掺杂染料DCJTB的白色有机电致发光器件

将Alq₃和DCJTB作为掺杂物与基质PVK按照不同比例混合共溶,旋涂成膜,制备了PVK∶Alq₃∶DCJTB为发光层的结构为ITO/ PVK∶Alq₃∶DCJTB/ BCP/Alq₃/LiF/Al的器件,其中Alq₃和BCP分别用作电子传输层和空穴阻挡层,PVK用作蓝光发光层和空穴传输层。保持PVK和DCJTB的质量比为100∶1不变,改变PVK和 Alq₃的质量比,当PVK和Alq3的质量比为20∶1时,得到了效果较好的白光。器件在电压为14 V时,色坐标达到(0.33,0.36),在10～14 V范围内变化甚微。     

基于卟啉化合物的异质结有机太阳能电池

采用混合溶剂制备了四苯基卟啉(TPP)及其铜配合物(TPPCu)和氯化对甲氧基四苯基铁卟啉(TMPPFeCl),将三种卟啉化合物和富勒烯的衍生物(PCBM)分别共混,制备异质结太阳能电池。器件结构是ITO/porphyrin∶PCBM/Al,研究此类电池的性能。结果显示基于TPP∶PCBM的器件性能最优,其短路电流密度(JSC)是0.98mA.cm-2,开路电压(VOC)是0.52V,填充因子(FF)为30.1%。TPP是三种卟啉化合物中最佳的给体材料。进而考察了TPP∶PCBM的不同浓度配比对器件性能的影响。TPP∶PCBM的最佳浓度配比为1∶1,增加或减少TPP的量都会使器件的短路电流和开路电压降低,对填充因子的影响不大。     

Fabrication and characterization of ZnTPP:PCBM bulk heterojunction (BHJ) solar cells

Bulk heterojunction (BHJ) solar cells were fabricated based on blended films of a porphyrin derivative 5,10,15,20-Tetraphenyl-21H,23H-porphine zinc (ZnTPP) and a fullerene derivative [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) as the active layer. The ZnTTP:PCBM BHJ solar cells were fabricated by spin-casting of the blended layer. The weight ratios of ZnTPP and PCBM were varied from 1:1 to 0:10. The electronic and optical properties of each cell were investigated. Optical density (OD) of the blended film for each cell was extracted from its reflection and transmission curves. OD and average absorption coefficients of the active materials were used to determine film thicknesses. Absorption spectra of each component material were compared with the spectra of the blended films. Current density–Voltage (J–V) characteristics were recorded under dark as well as under the illumination of AM 1.5G (1 sun) solar spectrum. The BHJ solar cell with ZnTPP:PCBM ratio of 1:9 showed the best performance . The values of RR, V_OC , J_SC , FF and η for these ratios were 106.3, 0.4 V, 1.316 mA/cm², 0.4 and 0.21%, respectively. The cross-section of this device using SEM was also examined.     

芴-咔唑新型共聚物/PVK掺杂体系的电致发光特性研究

研究了新型的芴-咔唑共聚物(PFC)与聚乙烯咔唑(PVK)掺杂体系的光致发光和电致发光特性.制备了结构分别为indium-tin-oxide(ITO)/PVK:PFC/bathocuproine(BCP)/tris-(8-hydroxylquinoline)-aluminum (Alq₃) /Mg:Ag，ITO/PFC/BCP/Alq₃/Mg∶Ag和ITO/PVK/BCP/Alq₃/Mg∶Ag的三种有机电致发光器件.对器件的光电特性进行了测试.结果表明，掺杂体系中的PVK有效地抑制了固态膜中PFC激基缔合物的形成.掺杂器件在不同的外加电场作用下发生发光层位置的移动，通过调节外加电场，可以获得从绿光到蓝光的可见光发射.当外加电压大于7V时，掺杂器件的蓝色发光亮度达到1650cd/m²，推测其中可能存在从PVK到PFC的能量传递过程.     

Transport mechanisms in tris(8-hydroxyquinoline)aluminium (Alq3) electronic layers: a study by photodipolar absorption

This paper describes the role of traps in the electronic conductivity of tris(8-hydroxyquinoline)aluminium (Alq3) in a conventional sandwich structure with indium tin oxide and aluminium electrodes. New results obtained by photodipolar absorption techniques and impedance spectroscopy are presented. The former method acts as a probe to highlight the role of traps. It is shown that optical pumping of electrons to trap levels gives a clear increase in dielectric absorption due to the reorientation of dipoles associated with trapped charges. The trap depth is estimated to be around E _t?=?0.19?eV, a value in good agreement with theoretical calculations and thermoluminescence measurements. The latter method permits a representation of the sample in terms of a circuit composed of a parallel capacitor (C _p) and resistor (R _p) both in series with a resistor R _s?≈?50?Ω located on the anode side. A logarithmic plot of R _p as a function of the dc bias voltage gives a linear law that is recognized, for the first time, to be a consequence of a trapped charge limited (TCL) current. The linearity can be improved by the introduction of a field-dependent mobility.     

The inverted solar cells with the polymer:fullerene blend film possessing a stratified composition profile

The inverted polymer:fullerene solar cells with structure of ITO/TiO₂/P3HT:PCBM/MoO₃/Al have been fabricated, where P3HT and PCBM stand for poly (3-hexylthiophene) and [6,6]-phenyl C₆₁-butyric acid methyl ester, respectively. It is discovered that the P3HT:PCBM blend film manipulated into the improved stratification structure, characterized as P3HT crystallite-rich zone close to the top surface and PCBM constituent-rich zone adjacent to the bottom surface, can offer nearly the same power conversion efficiency of solar cell, compared to the one grown into the bulk heterojunction structure, characterized as the bicontinuous interpenetrating network of P3HT and PCBM. We provide an alternative insight to the morphology control of inverted polymer:fullerene solar cells.     

Study of a ternary blend system for bulk heterojunction thin film solar cells

In this research, we report a bulk heterojunction(BHJ) solar cell consisting of a ternary blend system. Poly(3-hexylthiophene) P3 HT is used as a donor and [6,6]-phenyl C61-butyric acid methylester(PCBM) plays the role of acceptor whereas vanadyl 2,9,16,23-tetraphenoxy-29 H, 31H-phthalocyanine(VOPc Ph O) is selected as an ambipolar transport material. The materials are selected and assembled in such a fashion that the generated charge carriers could efficiently be transported rightwards within the blend. The organic BHJ solar cells consist of ITO/PEDOT:PSS/ternary BHJ blend/Al structure. The power conversion efficiencies of the ITO/ PEDOT:PSS/P3HT:PCBM/Al and ITO/PEDOT:PSS/P3HT:PCBM:VOPcPhO/Al solar cells are found to be 2.3% and 3.4%, respectively.     

Superstrate p-i-n a-Si:H solar cells on textured ZnO:Al front transparent conduction oxide

Superstrate p-i-n amorphous silicon thin-film (a-Si:H) solar cells are prepared on SnO₂:F and ZnO:Al transparent conducting oxides (TCOs) in order to see the effect of TCO/p-layers on a-Si:H solar cell operation. The solar cells prepared on textured ZnO:Al have higher open circuit voltage V_oc than cells prepared on SnO₂:F. The presence of a thin microcrystalline p-type silicon layer (μc-Si:H) between ZnO:Al and p a-SiC:H plays a major role by causing an improvement in the fill factor as well as in V_oc of a-Si:H solar cells prepared on ZnO:Al TCO. Without any treatment of the p-i interface, we could obtain a high V_oc of 994 mV while keeping the fill factor (72.7%) and short circuit current density J_sc at the same level as for the cells on SnO₂:F TCO. This high V_oc value can be attributed to modification in the current transport in this region due to creation of a potential barrier.     

Impact of nongeminate recombination on the performance of pristine and annealed P3HT:PCBM solar cells

Transient photovoltage (TPV) and voltage dependent charge extraction (CE) measurements were applied to poly(3‐hexyl‐thiophene) (P3HT):[6,6]‐phenyl‐C61 butyric acid methyl ester (PCBM) bulk heterojunction solar cells to analyze the limitations of solar cell performance in pristine and annealed devices. From the determined charge carrier decay rate under open circuit conditions and the voltage dependent charge carrier densities n (V), the nongeminate loss current j_loss of the device is accessible. We found that j_loss alone is sufficient to describe the j –V characteristics across the whole operational range, for annealed and, not yet shown before, also for the lower performing pristine solar cells. Even in a temperature range from 300 K to 200 K nongeminate recombination is found to be the dominant and, therefore, performance limiting loss process. Consequently, charge photogeneration is voltage independent in the voltage range studied. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

一种新型稀土配合物Tb(m-benzoicacid)3的发光特性的研究

研究了一种新型稀土配合物发光材料 ,对苯甲酸铽Tb(m benzoicacid) 3 的发光特性。以这种材料为掺杂剂 ,聚乙烯咔唑 (PVK)为基质材料制备了薄膜器件。通过对光谱的研究 ,发现在掺杂体系中 ,PVK与Tb(m benzoicacid) 3 之间存在有效的能量传递 ,能量传递效率与铽配合物的掺杂浓度有关 ,随着Tb配合物的掺杂浓度的增加 ,Tb的特征发光在掺杂体系中所占比重也相应增加 ,而PVK的发光相对明显减弱 ,当Tb(m benzoicacid) 3 :PVK的质量比高于 2 0 %时 ,整个体系的发光变为以Tb的发光为主 ,而PVK的发光基本猝灭了。以PVK :Tb(m benzoicacid) 3 掺杂体系为发光层 ,八羟基喹啉铝 (Alq)为电子传输层 ,制备了双层电致发光器件 ,器件的结构为ITO/PVK :Tb(m benzoicacid) 3 /Alq/LiF/Al,该器件的电致发光为三价铽离子的特征发光 ,在 2 1V的电压下 ,亮度可达 311nt。     

基于PVK和Alq3混合薄膜的光电性能研究

以PVK:Alq3混合体系作为研究对象,研究了该体系的光学性能以及电学性能.PVK:Alq3混合薄膜的光学性能表明在PVK和Alq3之间存在着能量传递,使得来自于Alq3的发光几乎占据了整个发光光谱.同时,光照下的电流电压曲线表明该体系具有明显的光伏效应.     

Reductive Fluorescence Quenching of the Photoexcited Free Base <Emphasis Type="Italic">meso</Emphasis>-Tetrakis (Pentafluorophenyl) Porphyrin by Amines

Steady state and time resolved fluorescence quenching behaviors of meso-Tetrakis (pentafluorophenyl) porphyrin (H₂F₂₀TPP) in presence of different aliphatic and aromatic amines have been executed in homogeneous dichloromethane (DCM) solution. At room temperature in DCM, free base (H₂F₂₀TPP) shows fluorescence with two distinct peaks at 640 and 711 nm and natural lifetime τ _f = 9.8 ns which are very similar to that of meso-tetraphenyl porphyrin (TPP). Unlike TPP, addition of both aliphatic and aromatic amines to a solution containing H₂F₂₀TPP results in an efficient decrease in fluorescence intensity without altering the shape and peak position of fluorescence emission. Upon addition of amines there was no change in optical absorption spectra of H₂F₂₀TPP. The fluorescence quenching rate constants ranged from 1 × 10⁹ to 4 × 10⁹ s⁻¹, which are one order below to the diffusion control limit, and temperature dependent quenching rate constants yield the activation energies which are found to be order of 0.1 eV. Femto second transient absorption studies reveal the existence of amine cation radical and porphyrin anion radicals with very short decay time (15 ps). The fluorescence quenching reaction follows Stern–Volmer kinetics. Steady state and time-resolved data are interpreted within general kinetic scheme of Marcus semi-classical model which attributes bimolecular electron transfer process between amines and the lowest excited singlet state of H₂F₂₀TPP. Calculated internal reorganization energies are found to be in between 0.04 and 0.22 ev. Variation of electron transfer rate as function of free energy change (∆G⁰) points the ET reactions in the present systems are in Marcus normal region. This is the first example of reductive fluorescence quenching of free base neutral porphyrins in homogeneous organic solvent ever known.     

MEH-PPV与TiO2共混体系太阳电池性能分析

以MEH-PPV(poly(2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylene vinylene)为电子给体材料(Donor,D), TiO₂纳米线为电子受体材料(Acceptor,A),制成了共混体系太阳电池. 从D/A材料共混体系的紫外可见吸收光谱(UV-vis)、光荧光谱(PL)、器件的电荷传输的光导J-V图等方面,分析了MEH-PPV∶TiO₂体系器件性能变化的原因. 得出了当在纯MEH-PP 关键词： 太阳电池 聚合物 性能     

Enhanced performance of light-emitting diodes based on a nanocomposite of dehydrated nanotube titanic acid and poly(vinylcarbazole) (PVK)

Performance of light-emitting diodes (LEDs) based on a nanocomposite of dehydrated nanotube titanic acid (DNTA) and poly(vinylcarbazole) (PVK) as emissive layer, i.e., ITO/PVK:DNTA(2 wt%)(100 nm)/BCP(30 nm)/Alq₃(10 nm)/LiF(1 nm)/Al [device D₂], was reported. By investigation of the luminance and electric characteristics of the device, we found that the performance of device D₂ was greatly improved. The recombination zone changed evidently due to the improvement of holes mobility. Compared with those devices without incorporating DNTA, both the maximum luminance and the electroluminescent efficiency of the device D₂ can be improved by a factor of three. Furthermore, the turn-on voltage of the device decreased dramatically.     

Influence of tetrabutylammonium hexafluorophosphate (TBAPF6) doping level on the performance of organic light emitting diodes based on PVK:PBD blend films

The effect of doping level of tetrabutylammonium hexafluorophosphate (TBAPF₆) on the performance of single-layer organic light emitting diodes (OLEDs) with ITO/PVK:PBD:TBAPF₆/Al structure were investigated where indium tin oxide (ITO) was used as anode, poly(9-vinylcarbazole) (PVK) as hole-transporting polymeric host, 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) as electron-transporting molecule and aluminium (Al) as cathode. It was found that the doped devices underwent a unique transition at the first voltage scan as indicated by drastically increasing of current at certain applied voltage. After the transition, the threshold voltage for current injection as well as the turn-on voltage decreased significantly as compared to the undoped device. The current injection threshold voltage and turn-on voltage decreased with the increase of TBAPF₆ doping level. More importantly, a relatively low current injection threshold voltage of 3 V has been achieved by doping a significant amount of TBAPF₆ (weight ratio greater than five) in the single-layer OLED based on PVK:PBD blend films with high work function Al metal as cathode. The significant improvement was attributed to the reduction of both electron and hole injection energy barriers caused by accumulation of ionic species at the interface.     

不同比例的MEH-PPV与PCBM共混体系光电池性能研究

以MEH-PPV(poly(2-methoxy-5-(2^/-ethylhexoxy)-1,4-phenylene vinylene)为电子给体材料(donor,D), PCBM(1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6)C₆₁)为电子受体材料(acceptor,A),制成了不同比例的共混体系太阳电池.从不同比例的D/A材料共混体系的原子力图、光荧光谱、器件的单电荷传输的暗导J-V图、太阳电池的光敏图及器件双电荷传输的光、暗导J-V图方面,详细分析了不同比例的D/A材料对器件性能影响.得出了当D/A材料比例为1∶4时,器件中活性层能形成良好的互穿网络,光生激子能有效地分离,被分离的电荷能有效地传输,太阳电池的性能最好.其光电池在100mW/cm²强度光照下,其开路电压V_oc为0.8V,短路电流密度J_sc为3.47mA/cm²,填充因子FF为55.9%,能量转换效率η为1.55%. 关键词： 太阳能电池 聚合物 性能     

Air stability of PTCDI‐C13‐based n‐OFETs on polymer interfacial layers

This Letter reports the novel use of poly(9‐vinylcarbazole) (PVK) as a dielectric interfacial layer for n‐type organic field‐effect transistors (n‐OFETs). With PVK, both the air stability and electron mobility of N,N′‐ditridecylperylene‐3,4,9,10‐tetracarboxylic diimide (PTCDI‐C13)‐based OFETs were improved. Among the PVKs with different weight‐average molecular weight (M_w), PVK with high M_w showed good performance. The high glass transition temperature of PVK enabled thermal post annealing of the active layer, which resulted in a high electron mobility of 0.61 cm²/Vs. This mobility was maintained at 90% and 59% after 4 days and 105 days in air, respectively. The PVK interfacial layer reduced the trapped charges in the PTCDI‐C13‐based n‐OFET for air‐exposure and caused a decrease in the threshold voltage shift.

     

High-brightness white light-emitting organic electroluminescent devices using poly(N-vinylcarbazole) as a hole-transporter

A white light-emitting organic electroluminescent (EL) device with multilayer thin-film structure, which shows high-brightness and high-efficiency, is demonstrated. The device structure of glass substrate/indium–tin oxide/poly(N-vinylcarbazole) (PVK)/1,1,4,4-tetraphenyl-1,3-butadiene/8-(quinolinolate)-aluminum (Alq) doped with 5,6,11,12-tetraphenylnaphthacene/Alq/Mg/Al was employed. The turn-on voltage is as low as 2.5 V. The white light emission covers a wide range of the visible region, and the Commission Internationale de 1' Eclairage coordinates of the emitted light are (0.319, 0.332) at 10 V. Bright white light, over 20 000 cd/m², was successfully obtained at about 18 V, and the maximum efficiency reaches to 1.24 lm/W at 9 V. The reasons of obtaining high level EL properties of our device have been discussed.     

倒置异质结有机太阳能电池的电子传输层

制备了结构为ITO/BCP或Alq3(x=0,2,6,10,20,40 nm)/C60(50 nm)/Rubrene(50 nm)/MoO3(5nm)/Al(130 nm)的倒置异质结有机太阳能电池,其中BCP或Alq3作电子传输层。实验结果表明:当BCP或Alq3≤6 nm时,器件性能随电子传输层厚度的变化不大;当BCP或Alq3≥10 nm时,随电子传输层厚度的增加,含Alq3器件的性能衰减很快,含BCP器件的性能衰减相对较慢,且其开路电压保持不变。分析表明:当电子传输层较薄时,粗糙的ITO使电子较容易从C60注入到ITO;当电子传输层较厚时,BCP/C60之间的能带弯曲使二者之间几乎不存在势垒,含BCP器件性能较差主要源于BCP较差的电子迁移率,而含Alq3器件性能较差主要源于Alq3/C60之间的势垒。     

Hole-transporting property of a chemically hybridized poly(vinylcarbazole)-fullerene

We synthesized a star copolymer of poly(vinylcarbazole) (PVK) branched from a fullerene (C₆₀) center, and investigated its optical absorption and photoluminescence properties. The chemically hybridized PVK-C₆₀ was then employed as a hole-transporting layer of the electroluminescent device with a poly(9,9^′-dihexylfluorene-2,7-divinylene-m-phenylenevinylene-stat-p-phenylenevinylene) (CPDHFPV) emitting layer. The ITO/PVK-C₆₀/CPDHFPV/LiF/Al device showed a strong electroluminescence quenching due to a direct contact of the PVK-C₆₀ and the CPDHFPV layers. In contrast, when an additional PVK layer was introduced between the two layers, the electroluminescence was largely enhanced. The emitted light power of the ITO/PVK-C₆₀/PVK/CPDHFPV/LiF/Al device was improved by 3 times compared with the device without the PVK-C₆₀ layer.