利用相容剂调控聚噻吩/富勒烯共混薄膜形貌

选择含有噻吩环的富勒烯衍生物([6,6]-噻吩基-C61-丁酸甲酯(TCBM-Cn,n代表在噻吩环5位的烷基链碳原子数))作为聚3-己基噻吩(P3HT)和[6,6]-苯基-C61-丁酸甲酯(PCBM)共混体系的相容剂,讨论了结晶能力不同的TCBM-Cn分子对共混体系相容性和P3HT结晶行为的影响.当使用强结晶性的相容剂TCBM-C0时,虽然不能完全抑制PCBM的聚集,但由于分子中噻吩环结构的存在,少量的相容剂即可提高P3HT的结晶度.而对于弱结晶性的相容剂TCBM-C6,虽然可以完全抑制PCBM的聚集,但是只有当其含量超过PCBM时,最终才能达到促进P3HT结晶的目的.     

纳米结构TiO2/聚3-己基噻吩多孔膜电极光电性能研究

用光电流作用谱、光电流-电势图等光电化学方法研究了ITO/聚3-己基噻吩(ITO/ P3HT)膜和纳米结构TiO2/聚3-己基噻吩(TiO2/P3HT)复合膜的光电转换性质. 结果表明, P3HT膜的禁带宽度为1.89 eV, 价带位置为－5.4 eV. 在ITO/TiO2/ P3HT复合膜电极中存在p-n异质结, 在一定条件下异质结的存在有利于光生电子-空穴对的分离. P3HT修饰ITO/TiO2电极可使光电流发生明显的红移, 从而提高了宽禁带半导体的光电转换效率.     

外场对聚(3-己基噻吩)溶液结晶行为的影响

以聚(3-己基噻吩)(P3HT)为研究对象,借助紫外-可见光谱与原子力显微镜,详细考察了旋转剪切场、紫外光照射、超声处理3种外场对P3HT/混合溶剂(CHCl3-CH2Cl2)体系结晶行为的影响,此外,还研究了P3HT溶液结晶的"记忆效应"。研究表明:旋转场能够显著提高P3HT的结晶度,而紫外光照射和超声处理易使溶液中分子链的活动性增加,对结晶性的影响不显著;施加外场并没有改变溶液中纳米线的聚集形式,仍为H聚集;P3HT溶液的初始态不同,其结晶过程中的晶体微结构及形貌也会发生变化。     

石墨烯表面接枝聚(3-己基噻吩)分子刷的制备与表征

结合高效率重氮盐加成和Kumada催化-转移缩聚反应(KCTP),聚3-己基噻吩(P3HT)被共价接枝在石墨烯(GN)表面,形成聚合物分子刷(P3HT-GN).通过重氮盐偶合反应,溴苯分子首先被共价连接在氧化还原方法制备的GN表面,由此锚固的Ni(PPh3)4随后引发3-己基噻吩的催化-转移聚合.原子力显微和热失重分析结果表明,接枝在GN表面的P3HT分子刷厚度约为5 nm,重量分数为20.1%.当假设P3HT以伸直链构象接枝在GN表面时,估计的接枝密度为每6.53 nm2含有1个P3HT链,链间平均距离为2.556 nm.P3HT-GNs的X射线衍射在扫描范围内没有GN层间衍射峰出现,表明接枝后的GN是很好剥离的.P3HT-GN的紫外-可见光谱在300～500 nm范围内显示有比纯P3HT更弱的吸收峰,表明P3HT与GN之间存在显著的相互作用,与X-射线光电子能谱中增大的氧化噻吩环含量的结果是一致的.P3HT与GN的强相互作用使得光诱导产生的荧光几乎完全被淬灭,量子产率仅为0.042%,相当于纯P3HT的1/80,显示了突出的电荷转移效率.     

溶剂沸点对聚(3-己基噻吩)薄膜内链结构与分子取向的影响

以聚(3-己基噻吩)(P3HT)为研究对象,借助荧光相关光谱、紫外-可见光谱和掠角红外光谱考察了溶剂性质对旋涂膜内P3HT的链结构与分子取向的影响。结果表明:溶液中P3HT的分子链构象受溶解度的影响,当P3HT溶解在溶解性好的良溶剂中时,链构象更伸展;固体薄膜内P3HT的物理结构却不受其在溶剂中溶解度大小的影响而具有沸点依赖性,溶解在高沸点溶剂中的P3HT旋涂后,薄膜内P3HT主链平面性与π-π相互作用均得到提高;此外,溶剂沸点的增加导致分子取向由"面朝上"方式转变为"边朝上"方式。     

应用混合溶剂制备高性能聚噻吩有机薄膜晶体管

采用良溶剂与不良溶剂混合的方法,提高了聚3-己基噻吩(P3HT)薄膜晶体管的场效应迁移率.UV-Vis吸收光谱、掠角X-射线衍射和原子力显微镜研究表明,通过向P3HT的氯仿溶液中加入适量二氧六环可以增强溶液分子间π-π相互作用,在溶液中形成分子链有序排列的P3HT聚集体,从而提高了旋涂得到的聚合物薄膜结晶度,并控制分子沿着有利于电荷传输方向排列.薄膜的场效应迁移率在二氧六环的含量为10vol%时达到最高值1.7×10-2 cm2 V-1 s-1,与纯氯仿溶液制得的P3HT薄膜的迁移率相比提高了50多倍.     

一种基于聚噻吩-聚硒吩全共轭嵌段共聚物的合成及性质研究

全共轭刚性-刚性嵌段共聚物兼具嵌段共聚物的微相分离特性和共轭聚合物的光电性能，引起了人们越来越多的关注.基于此，我们利用格氏置换（GRIM）方法合成了全共轭刚性-刚性嵌段共聚物聚（3-己基硒吩）-b-聚（3-（6-羟基）-己基噻吩）（P3HS-b-P3HHT）.通过在噻吩段的烷基侧链末端引入羟基基团来丰富全共轭体系的溶液结构，并利用羟基的热交联特性提高聚噻吩均聚物的薄膜场效应晶体管的热稳定性.一方面，通过溶剂共混（氯仿/吡啶和甲醇/吡啶混合溶剂），调控P3HS-b-P3HHT分子在混合溶剂中的刚性-刚性相互作用，使P3HS-b-P3HHT在混合溶剂中自组装形成不同的纳米结构，如纳米带、纳米纤维和纳米微球等.另一方面，将P3HS-b-P3HHT和聚（3-己基噻吩）（P3HT）共混，利用羟基之间的热交联，使P3HS-b-P3HHT/P3HT共混薄膜在薄膜场效应晶体管中表现出较好的热稳定性.     

小分子优先结晶构筑聚合物/非富勒烯共混体系互穿网络结构

非富勒烯小分子受体(SMAs)有序聚集决定聚合物/非富勒烯共混体系光伏电池的双分子复合几率。 然而,由于非对称相分离聚合物趋于优先形成网络,抑制小分子受体分子结晶。 在聚[(2,6-(4,8-二(5-(2-乙基己基噻吩-2-基)苯并[1,2-b:4,5-b']二噻吩))-alt-(5,5-(1',3'-二-2-噻吩基-5',7'-二(2-乙基己基)苯并[1',2'-c:4',5'-c']二噻吩-4,8-二酮))](PBDB-T)/9-二(2-亚甲基(3-(1,1-二氰基亚甲基)-6,7-二氟-茚酮))-5,5,11,11-四(4-己基苯基)-二噻吩并[2,3-d:2',3'-d']-s-引达省[1,2-b:5,6-b']二噻吩(IT-4F)共混体系,四氢呋喃蒸汽处理可提高IT-4F结晶性,150 ℃热退火可提高PBDB-T的结晶性。 因此,依次利用蒸汽退火和热退火处理薄膜,诱导小分子先结晶、聚合物后结晶,从而降低PBDB-T对小分子扩散的限制,构建高结晶互穿网络结构。 形貌优化后降低了双分子复合,器件光电转换效率从5.95%提高至7.18%。     

基底温度对刮涂制备的P3HT:PCBM薄膜形貌和光伏电池性能的影响

研究了刮涂制备P3HT:PCBM(P3HT:聚3-己基噻吩,PCBM:[6,6]-苯基-C61-丁酸甲酯)活性层的过程中,基底温度对P3HT:PCBM活性层薄膜性质和电池性能的影响.结果表明,提高基底温度在缩短薄膜干燥时间的同时,抑制了PCBM相的大尺度聚集,并改善了P3HT:PCBM薄膜中P3HT在(100)方向上的结晶程度,但降低了π-π共轭方向上的有序度.制备的光伏电池经过进一步退火处理后可形成良好的互穿网络结构,能量转换效率可达3.93％.     

P3HT/CdS/TiO2/ZnO一维有序核壳式纳米棒阵列的构制及其在杂化太阳电池中的应用研究

采用恒电位法在铟锡氧化物导电玻璃(ITO)上制备了高度有序一维ZnO纳米棒阵列,将ZnO纳米棒阵列在TiO2溶胶中采用提拉法制备出了一维TiO2/ZnO核壳式纳米棒阵列.在一维TiO2/ZnO核壳式纳米棒阵列上电沉积CdS纳米晶得到一维CdS/TiO2/ZnO核壳式纳米棒阵列,然后在一维CdS/TiO2/ZnO核壳式纳米棒阵列上电沉积聚3-己基噻吩(P3HT)薄膜得到P3HT/CdS/TiO2/ZnO核壳式纳米结构薄膜.以该纳米结构薄膜电极为光阳极制备出新型纳米结构杂化太阳电池,研究了该类电池的光电转换性能,初步探讨了该类电池的工作机理.     

Thermal stability of P3HT and P3HT:PCBM blends in the molten state

The thermal stability of poly(3-hexylthiophene) (P3HT) in its molten state was investigated in air and nitrogen atmospheres under no illumination conditions, with the aim of testing the feasibility of processing it using polymer melt techniques. A large set of different experimental characterization techniques was used including thermogravimetric analysis (TGA), rotational rheometry, infrared spectroscopy (FTIR-ATR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), gel permeation chromatography (GPC), UV-Vis and fluorescence spectroscopy. The results obtained strongly suggest that the processing of P3HT in its molten state is possible, without noticeable degradation, if carried out under nitrogen atmosphere and if the processing (residence) times are relatively short. Conversely, as expected, in a normal air atmosphere P3HT degrades rapidly at temperatures above its melting point. The effect of PCBM on the thermal stability of P3HT:PCBM blends in the molten state was also studied using TGA, and in air atmosphere PCBM is shown to delay oxidation.     

Ultrafast photoinduced charge separation dynamics in polythiophene/SnO2 nanocomposites

We present a study of photoinduced interfacial electron transfer (ET) dynamics of SnO2 nanocrystalline thin films sensitized by polythiophene derivatives (regioregular poly(3-hexylthiophene) (P3HT) and regiorandom poly(3-undecyl-2,2'-bithiophene) (P3UBT)). ET dynamics were measured by following the dynamics of injected electrons in SnO2 and polarons in the conjugated polymer using ultrafast mid-IR transient absorption spectroscopy. The rate of electron transfer from P3HT and P3UBT to SnO2 films was determined to occur on sub-picosecond time scale (120 +/- 20 fs). In P3HT/SnO2 composite, interchain charge transfer was found to compete with and reduce the quantum efficiency of interfacial electron transfer at high polymer loading. This interchain charge separation processes can be reduced in non-regioregular polymer or at low polymer loading levels.     

Ideal spread monolayer and multilayer formation of fully hydrophobic polythiophenes via liquid crystal hybridization on water

The spread monolayer formation of hydrophobic poly(3-alkylthiophene)s (P3ATs), regioregular poly(3-hexylthiophene) ( HT-P3HT), regioregular poly(3-dodecylthiophene) ( HT-P3DT), and regioirregular poly(3-hexylthiophene) ( RI-P3HT), were attained on the water surface via cospreading with a liquid-crystal molecule, 4'-pentyl-4-cyanobiphenyl (5CB). The spread monolayers were characterized by pi- A isotherms, Brewster angle microscopy (BAM), and atomic force microscopy (AFM). The molecular area for the cospread mixtures of P3ATs and 5CB expanded more than that of pure P3ATs as shown from the pi-A isotherms. BAM revealed that the mixed film forms the monomolecularly uniform and flat films on water. AFM elucidated that the spread monolayer of the hydrophobic P3ATs formed on the top of the 5CB monolayer on water with thicknesses of ca. 1.6 and ca. 2.6 nm for the two P3HTs and HT-P3DT, respectively. The P3AT/5CB hybrid monolayers could be fully transferred onto a solid substrate, and pure P3AT monolayers were obtained after volatilization of 5CB by gentle heating. The multilayer formation of pure P3AT monolayers was prepared by layer-by-layer deposition involving repeating horizontal deposition and successive volatilization of 5CB. Grazing angle incidence X-ray diffraction measurements showed that the lamella plane of the P3ATs is perfectly oriented parallel to the substrate plane in the resulting thin films. This shows a marked contrast with those obtained by spin casting using the identical polymer, where both in-plane and out-of-plane lamellae are involved. These thin films with perfectly controlled lamella orientation should be of great significance as the model system for evaluating the charge mobility for organic polymer electric devices.     

Oriented poly(3-hexylthiophene) nanofibril with the π-π stacking growth direction by solvent directional evaporation

In this article, the uniaxial alignment of poly(3-hexylthiophene) (P3HT) nanofibrils with a π-π stacking growth direction in which P3HT chains adopt a flat-on conformation was obtained by solvent directional evaporation using a glass cover slide and a poly(dimethylsiloxane) (PDMS) sheet to press the P3HT film in a carbon disulfide (CS(2)) atmosphere. By controlling the CS(2) vapor pressure during the film-forming process, we got a well-oriented P3HT film whose order parameter reached as high as 0.97. The orientation of the film was induced by the crystallization nucleation of P3HT and the directional evaporation of the solvent. Under a CS(2) vapor atmosphere, P3HT crystals preferred to adopt the form II modification, which started by nucleation. Owing to the solvent directional evaporation from the center to the margin, P3HT at the center of the sample would precipitate first to induce nucleation. Then the peripheral P3HT would directly diffuse, precipitate, and then adhere to the nucleus to form the uniaxial alignment of P3HT nanofibrils along the direction of solvent evaporation. Furthermore, in the P3HT nanofibrils, the π-π stacking direction of P3HT lamellae was parallel to the crystal growth direction, which would provide an effective path for charge transport.     

Role of structural order and excess energy on ultrafast free charge generation in hybrid polythiophene/Si photovoltaics probed in real time by near-infrared broadband transient absorption

Despite the central role of light absorption and the subsequent generation of free charge carriers in organic and hybrid organic-inorganic photovoltaics, the precise process of this initial photoconversion is still debated. We employ a novel broadband (UV-Vis-NIR) transient absorption spectroscopy setup to probe charge generation and recombination in the thin films of the recently suggested hybrid material combination poly(3-hexylthiophene)/silicon (P3HT/Si) with 40 fs time resolution. Our approach allows for monitoring the time evolution of the relevant transient species under various excitation intensities and excitation wavelengths. Both in regioregular (RR) and regiorandom (RRa) P3HT, we observe an instant (<40 fs) creation of singlet excitons, which subsequently dissociate to form polarons in 140 fs. The quantum yield of polaron formation through dissociation of delocalized excitons is significantly enhanced by adding Si as an electron acceptor, revealing ultrafast electron transfer from P3HT to Si. P3HT/Si films with aggregated RR-P3HT are found to provide free charge carriers in planar as well as in bulk heterojunctions, and losses are due to nongeminate recombination. In contrast for RRa-P3HT/Si, geminate recombination of bound carriers is observed as the dominant loss mechanism. Site-selective excitation by variation of pump wavelength uncovers an energy transfer from P3HT coils to aggregates with a 1/e transfer time of 3 ps and reveals a factor of 2 more efficient polaron formation using aggregated RR-P3HT compared to disordered RRa-P3HT. Therefore, we find that polymer structural order rather than excess energy is the key criterion for free charge generation in hybrid P3HT/Si solar cells.     

Catalyst-transfer polycondensation. mechanism of Ni-catalyzed chain-growth polymerization leading to well-defined poly(3-hexylthiophene)

We studied the mechanism of the chain-growth polymerization of 2-bromo-5-chloromagnesio-3-hexylthiophene (1) with Ni(dppp)Cl2 [dppp = 1,3-bis(diphenylphosphino)propane], in which head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a low polydispersity is obtained and the M(n) is controlled by the feed ratio of the monomer to the Ni catalyst. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that the HT-P3HT uniformly had a hydrogen atom at one end of each molecule and a bromine atom at the other. The reaction of the polymer with aryl Grignard reagent gave HT-P3HT with aryl groups at both ends, which indicates that the H-end was derived from the propagating Ni complex. The degree of polymerization and the absolute molecular weight of the polymer could be evaluated from the 1H NMR spectra of the Ar/Ar-ended HT-P3HT, and it was found that one Ni catalyst molecule forms one polymer chain. Furthermore, by reaction of 1 with 50 mol % Ni(dppp)Cl2, the chain initiator was found to be a bithiophene-Ni complex, formed by a coupling reaction of 1 followed by insertion of the Ni(0) catalyst into the C-Br bond of the dimer. On the basis of these results, we propose that this chain-growth polymerization involves the coupling reaction of 1 with the polymer via the Ni catalyst, which is transferred intramolecularly to the terminal C-Br bond of the elongated molecule. We call this mechanism "catalyst-transfer polycondensation".     

Understanding of morphology evolution in local aggregates and neighboring regions for organic photovoltaics

Fluorescence intensity and its ratio mapping combined with time-dependent optical microscopy and atomic force microscopy (AFM) were used to understand morphology evolution of local aggregates and neighboring regions for organic solar cells. Three solvents with different boiling points including chlorobenzene (CB), 1,3-dichlorobenzene (1,3-DCB) and 1,2-dichlorobenzene (1,2-DCB) were used to engineer morphology. These solvents affected morphology evolution factors such as solvent evaporation rate, formation (e.g., growth rate, size and/or quantity) of (6,6)-phenyl-C61-butric-acid methyl ester (PCBM)-rich aggregates, and packing/ordering of poly(3-hexylthiophene) (P3HT). Three local regions (1, 2 and 3) including microscale aggregates and their surrounding areas were identified to explore the mechanism of morphology evolution. Region 1 was the PCBM-rich aggregates; region 2 was the PCBM-deficient area; and region 3 was the area composed of a relatively normal P3HT/PCBM composite beyond region 2 for each solvent. The intensity of fluorescence spectra decreased as region 1 > region 2 > region 3 in thermally annealed (140 °C, 20 min) P3HT/PCBM blend film from each solvent. The highest fluorescence intensity in region 1 was probably caused by the relatively poor phase separation where both PCBM and P3HT formed large isolated domains. The higher fluorescence intensity ratio (720 nm/650 nm) suggested a larger relative amount of PCBM molecules, supported by similar morphologies in fluorescence intensity ratio mapping compared to those in optical images. The fluorescence intensity ratio was with the order of region 1 > region 3 > region 2 in both CB and 1,3-DCB based films, but with region 1 > region 2 > region 3 for the 1,2-DCB based film. The order of effective area taken up by aggregates was CB > 1,3-DCB > 1,2-DCB in annealed (140 °C, 10 min) bulk blend films. The final solar cell performance agreed with morphology results. This work is imperative with regards to revealing the mechanism of morphology evolution in local aggregates and surrounding regions for organic photovoltaic films.     

Thiophene-substituted fulleropyrrolidine derivatives as acceptor molecules in a thin film organic solar cell

A study of the design of thiophene-substituted fulleropyrrolidine derivatives as the acceptor in photovoltaic cells has been carried out using poly(3-hexylthiophene) (P3HT) as the model donor polymer. It was found that five types of thiophene-substituted fulleropyrrolidine worked as a good acceptor partner with P3HT, and the highest power conversion efficiency (PCE) was obtained for 1-(2-(2-methoxyethoxy)ethyl)-2-(2-thiophen-2-yl)fulleropyrrolidine (2.99%); this is superior to that of the P3HT polymer including methyl [C60]-PCBM under the same experimental conditions.     

Dynamic structure of regioregulated poly(alkylthiophene)s

Solid-state structures of regioregulated poly(3-hexylthiophene) (P3HT) and poly(3-butylthiophene) (P3BT) were investigated using Fourier transform infrared absorption (FT-IR) spectroscopy. This study revealed that a twist glass transition of thiophene twisting for P3HT exists around 300 K ( T gp). Additionally, the influence of annealing on population of glassy crystal, crystal, and plastic crystal phases was explored. The annealed sample is dominated by plastic crystal phase, and this phase increases with annealing temperature below T gp. The frustration against crystallization in P3HT is weaker than that in P3BT. Consequently, the plastic crystal phase is formed as a dominant structure, whereas P3BT forms both a well-defined crystal in the conventional sense and glassy crystal.