共查询到20条相似文献,搜索用时 15 毫秒
1.
Edward J. W. Crossland Khosrow Rahimi Günter Reiter Ullrich Steiner Sabine Ludwigs 《Advanced functional materials》2011,21(3):518-524
While molecular ordering via crystallization is responsible for many of the impressive optoelectronic properties of thin‐film semiconducting polymer devices, crystalline morphology and its crucial influence on performance remains poorly controlled and is usually studied as a passive result of the conditions imposed by film deposition parameters. A method for systematic control over crystalline morphology in conjugated polymer thin films by very precise control of nucleation density and crystal growth conditions is presented. A precast poly(3‐hexylthiophene) film is first swollen into a solution‐like state in well‐defined vapor pressures of a good solvent, while the physical state of the polymer chains is monitored using in situ UV–vis spectroscopy and ellipsometry. Nucleation density is selected by a controlled deswelling of the film or by a self‐seeding approach using undissolved crystalline aggregates that remain in the swollen film. Nucleation densities ranging successively over many orders of magnitude are achieved, extending into the regime of spherulitic domains 10 to 100 μm in diameter, a length scale highly relevant for typical probes of macroscopic charge transport such as field‐effect transistors. This method is presented as a tool for future systematic study of the structure‐function relation in semicrystalline semiconducting polymers in a broad range of applications. 相似文献
2.
Wibren D. Oosterbaan Jean‐Christophe Bolsée Abay Gadisa Veerle Vrindts Sabine Bertho Jan D'Haen Thomas J. Cleij Laurence Lutsen Christopher R. McNeill Lars Thomsen Jean V. Manca Dirk Vanderzande 《Advanced functional materials》2010,20(5):792-802
The field‐effect transistor (FET) and diode characteristics of poly(3‐alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n‐alkyl‐side‐chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV–vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K‐edge near edge X‐ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl‐chain‐length‐dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side‐chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films. 相似文献
3.
On the Relation between Morphology and FET Mobility of Poly(3‐alkylthiophene)s at the Polymer/SiO2 and Polymer/Air Interface 下载免费PDF全文
Wibren D. Oosterbaan Jean‐Christophe Bolsée Linjun Wang Veerle Vrindts Laurence J. Lutsen Vincent Lemaur David Beljonne Lars Thomsen Jean V. Manca Dirk J. M. Vanderzande 《Advanced functional materials》2014,24(14):1994-2004
The influence of the interface of the dielectric SiO2 on the performance of bottom‐contact, bottom‐gate poly(3‐alkylthiophene) (P3AT) field‐effect transistors (FETs) is investigated. In particular, the operation of transistors where the active polythiophene layer is directly spin‐coated from chlorobenzene (CB) onto the bare SiO2 dielectric is compared to those where the active layer is first spin‐coated then laminated via a wet transfer process such that the film/air interface of this film contacts the SiO2 surface. While an apparent alkyl side‐chain length dependent mobility is observed for films directly spin‐coated onto the SiO2 dielectric (with mobilities of ≈10?3 cm2 V?1 s?1 or less) for laminated films mobilities of 0.14 ± 0.03 cm2 V?1 s?1 independent of alkyl chain length are recorded. Surface‐sensitive near edge X‐ray absorption fine structure (NEXAFS) spectroscopy measurements indicate a strong out‐of‐plane orientation of the polymer backbone at the original air/film interface while much lower average tilt angles of the polymer backbone are observed at the SiO2/film interface. A comparison with NEXAFS on crystalline P3AT nanofibers, as well as molecular mechanics and electronic structure calculations on ideal P3AT crystals suggest a close to crystalline polymer organization at the P3AT/air interface of films from CB. These results emphasize the negative influence of wrongly oriented polymer on charge carrier mobility and highlight the potential of the polymer/air interface in achieving excellent “out‐of‐plane” orientation and high FET mobilities. 相似文献
4.
LinJun Wang Gerold M. Rangger Lorenz Romaner Georg Heimel Tomas Bučko ZhongYun Ma QiKai Li Zhigang Shuai Egbert Zojer 《Advanced functional materials》2009,19(23):3766-3775
Modifying metal electrodes with self‐assembled monolayers (SAMs) has promising applications in organic and molecular electronics. The two key electronic parameters are the modification of the electrode work function because of SAM adsorption and the alignment of the SAM conducting states relative to the metal Fermi level. Through a comprehensive density‐functional‐theory study on a series of organic thiols self‐assembled on Au(111), relationships between the electronic structure of the individual molecules (especially the backbone polarizability and its response to donor/acceptor substitutions) and the properties of the corresponding SAMs are described. The molecular backbone is found to significantly impacts the level alignment; for molecules with small ionization potentials, even Fermi‐level pinning is observed. Nevertheless, independent of the backbone, polar head‐group substitutions have no effect on the level alignment. For the work‐function modification, the larger molecular dipole moments achieved when attaching donor/acceptor substituents to more polarizable backbones are largely compensated by increased depolarization in the SAMs. The main impact of the backbone on the work‐function modification thus arises from its influence on the molecular orientation on the surface. This study provides a solid theoretical basis for the fundamental understanding of SAMs and significantly advances the understanding of structure–property relationships needed for the future development of functional organic interfaces. 相似文献
5.
A novel method making use of block copolymer self‐assembly in nematic liquid crystals (LCs) is described for preparing macroscopically oriented nanofibrils of π‐conjugated semiconducting polymers. Upon cooling, a diblock copolymer composed of regioregular poly(3‐hexylthiophene) (P3HT) and a liquid crystalline polymer (LCP) in a block‐selective LC solvent can self‐assemble into oriented nanofibrils exhibiting highly anisotropic absorption and polarized photoluminescence emission. An unusual feature of the nanofibrils is that P3HT chains are oriented along the fibrils' long axis. This general method makes it possible to use LCs as an anisotropic medium to grow oriented nanofibrils of many semiconducting polymers insoluble in LCs. 相似文献
6.
Controlling Polymorphism in Poly(3‐Hexylthiophene) through Addition of Ferrocene for Enhanced Charge Mobilities in Thin‐Film Transistors 下载免费PDF全文
Brandon H. Smith Michael B. Clark Jr. Hao Kuang Christopher Grieco Alec V. Larsen Chenhui Zhu Cheng Wang Alexander Hexemer John B. Asbury Michael J. Janik Enrique D. Gomez 《Advanced functional materials》2015,25(4):542-551
Crystalline organic molecules often exhibit the ability to assemble into multiple crystal structures depending on the processing conditions. Exploiting this polymorphism to optimize molecular orbital overlap between adjacent molecules in the unit lattice is an effective method for improving charge transport within the material. In this study, grazing incident X‐ray diffraction was employed to demonstrate the formation of tighter π‐π stacking poly(3‐hexylthiophene‐2,5‐diyl) polymorphs in films spin coated from ferrocene‐containing solutions. As a result, the addition of ferrocene to casting solutions yields thin‐film transistors which exhibit approximately three times higher source‐drain currents and charge mobilities than neat polymer devices. Nevertheless, XPS depth profiling and NMR analyses of the active layer reveal that all ferrocene is removed during the spin coating process, which may be an essential factor to achieve high mobilities. Such insights gleaned from ferrocene/poly(3‐hexylthiophene‐2,5‐diyl) mixtures can serve as a template for selection and optimization of other small molecule/polymer systems with greater baseline charge mobilities. 相似文献
7.
Mechanism of Crystallization and Implications for Charge Transport in Poly(3‐ethylhexylthiophene) Thin Films 下载免费PDF全文
Duc T. Duong Victor Ho Zhengrong Shang Sonya Mollinger Stefan C.B. Mannsfeld Javier Dacuña Michael F. Toney Rachel Segalman Alberto Salleo 《Advanced functional materials》2014,24(28):4515-4521
In this work, crystallization kinetics and aggregate growth of poly(3‐ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X‐ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also determined that crystallization kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and average molecular weight. Time‐dependent, field‐effect hole mobilities in thin films reveal a percolation threshold for both low and high molecular weight P3EHT. Structural analysis reveals that charge percolation requires bridged aggregates separated by a distance of ≈2–3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie molecules and inter‐aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystallization kinetics. 相似文献
8.
Quantifying the Energy Barriers and Elucidating the Charge Transport Mechanisms across Interspherulite Boundaries in Solution‐Processed Organic Semiconductor Thin Films 下载免费PDF全文
Anna K. Hailey Szu‐Ying Wang Marcia M. Payne John E. Anthony Vitaly Podzorov Yueh‐Lin Loo 《Advanced functional materials》2015,25(35):5662-5668
Grain boundaries act as bottlenecks to charge transport in devices comprising polycrystalline organic active layers. To improve device performance, the nature and resulting impact of these boundaries must be better understood. The densities and energy levels of shallow traps within and across triethylsilylethynyl anthradithiophene (TES ADT) spherulites are quantified. The trap density is 7 × 1010 cm?2 in devices whose channels reside within a single spherulite and up to 3 × 1011 cm?2 for devices whose channels span a spherulite boundary. The activation energy for charge transport, EA, increases from 34 meV within a spherulite to 50–66 meV across a boundary, depending on the angle of molecular mismatch. Despite being molecular in nature, these EA’s are more akin to those found for charge transport in polymer semiconductors. Presumably, trapped TES ADT at the boundary can electrically connect neighboring spherulites, similar to polymer chains connecting crystallites in polymer semiconductor thin films. 相似文献
9.
Regioregular poly(3‐hexyl thiophene) (RR P3HT) is drop‐cast to fabricate field‐effect transistor (FET) devices from different solvents with different boiling points and solubilities for RR P3HT, such as methylene chloride, toluene, tetrahydrofuran, and chloroform. A Petri dish is used to cover the solution, and it takes less than 30 min for the solvents to evaporate at room temperature. The mesoscale crystalline morphology of RR P3HT thin films can be manipulated from well‐dispersed nanofibrils to well‐developed spherulites by changing solution processing conditions. The morphological correlation with the charge‐carrier mobility in RR P3HT thin‐film transistor (TFT) devices is investigated. The TFT devices show charge‐carrier mobilities in the range of 10–4 ~ 10–2 cm2 V–1 s–1 depending on the solvent used, although grazing‐incidence X‐ray diffraction (GIXD) reveals that all films develop the same π–π‐stacking orientation, where the <100>‐axis is normal to the polymer films. By combining results from atomic force microscopy (AFM) and GIXD, it is found that the morphological connectivity of crystalline nanofibrils and the <100>‐axis orientation distribution of the π–π‐stacking plane with respect to the film normal play important roles on the charge‐carrier mobility of RR P3HT for TFT applications. 相似文献
10.
Photoinduced Anisotropic Supramolecular Assembly and Enhanced Charge Transport of Poly(3‐hexylthiophene) Thin Films 下载免费PDF全文
Mincheol Chang Jiho Lee Nabil Kleinhenz Boyi Fu Elsa Reichmanis 《Advanced functional materials》2014,24(28):4457-4465
The self‐organization of organic polymer semiconductors into ordered supramolecular assemblies commensurate with efficient charge transport is achieved by tuning a range of process parameters (e.g., film deposition method (spin vs drop cast), solvent boiling point (low vs high boiling point), polymer‐dielectric interface treatment, and post‐deposition processing (solvent vapor or thermal annealing)). However, these strategies present limitations for large‐scale high‐throughput processing due to associated pre‐ and/or post semiconductor deposition steps. Here, photoinduced anisotropic supramolecular assembly of P3HT chains in solution is demonstrated. UV irradiation provides for enhanced intramolecular ordering of solubilized polymer chains, and thereby effects formation of anisotropic supramolecular polymer assemblies via favorable π–π stacking (intermolecular interaction). Molecular ordering is thus dramatically enhanced with concomitant, enhanced charge transport characteristics of corresponding films. Additional pre‐ and/or post treatments are avoided. 相似文献
11.
Brendan O'Connor R. Joseph Kline Brad R. Conrad Lee J. Richter David Gundlach Michael F. Toney Dean M. DeLongchamp 《Advanced functional materials》2011,21(19):3697-3705
A novel method of strain‐aligning polymer films is introduced and applied to regioregular poly(3‐hexylthiophene) (P3HT), showing several important features of charge transport. The polymer backbone is shown to align in the direction of applied strain resulting in a large charge‐mobility anisotropy, where the in‐plane mobility increases in the applied strain direction and decreases in the perpendicular direction. In the aligned film, the hole mobility is successfully represented by a two‐dimensional tensor, suggesting that charge transport parallel to the polymer backbone within a P3HT crystal is strongly favored over the other crystallographic directions. Hole mobility parallel to the backbone is shown to be high for a mixture of plane‐on and edge‐on packing configurations, as the strain alignment is found to induce a significant face‐on orientation of the originally highly edge‐on oriented crystalline regions of the film. This alignment approach can achieve an optical dichroic ratio of 4.8 and a charge‐mobility anisotropy of 9, providing a simple and effective method to investigate charge‐transport mechanisms in polymer semiconductors. 相似文献
12.
Patrick Pingel Achmad Zen Ruben D. Abellón Ferdinand C. Grozema Laurens D.A. Siebbeles Dieter Neher 《Advanced functional materials》2010,20(14):2286-2295
Previous investigations of the field‐effect mobility in poly(3‐hexylthiophene) (P3HT) layers revealed a strong dependence on molecular weight (MW), which was shown to be closely related to layer morphology. Here, charge carrier mobilities of two P3HT MW fractions (medium‐MW: Mn = 7 200 g mol?1; high‐MW: Mn = 27 000 g mol?1) are probed as a function of temperature at a local and a macroscopic length scale, using pulse‐radiolysis time‐resolved microwave conductivity (PR‐TRMC) and organic field‐effect transistor measurements, respectively. In contrast to the macroscopic transport properties, the local intra‐grain mobility depends only weakly on MW (being in the order of 10?2 cm2 V?1 s?1) and being thermally activated below the melting temperature for both fractions. The striking differences of charge transport at both length scales are related to the heterogeneity of the layer morphology. The quantitative analysis of temperature‐dependent UV/Vis absorption spectra according to a model of F. C. Spano reveals that a substantial amount of disordered material is present in these P3HT layers. Moreover, the analysis predicts that aggregates in medium‐MW P3HT undergo a “pre‐melting” significantly below the actual melting temperature. The results suggest that macroscopic charge transport in samples of short‐chain P3HT is strongly inhibited by the presence of disordered domains, while in high‐MW P3HT the low‐mobility disordered zones are bridged via inter‐crystalline molecular connections. 相似文献
13.
Highly Efficient Inverted Organic Solar Cells Through Material and Interfacial Engineering of Indacenodithieno[3,2‐b]thiophene‐Based Polymers and Devices 下载免费PDF全文
Jeremy J. Intemann Kai Yao Yong‐Xi Li Hin‐Lap Yip Yun‐Xiang Xu Po‐Wei Liang Chu‐Chen Chueh Fei‐Zhi Ding Xi Yang Xiaosong Li Yiwang Chen Alex K.‐Y. Jen 《Advanced functional materials》2014,24(10):1465-1473
A synergistic approach combining new material design and interfacial engineering of devices is adopted to produce high efficiency inverted solar cells. Two new polymers, based on an indacenodithieno[3,2‐b]thiophene‐difluorobenzothiadiazole (PIDTT‐DFBT) donor–acceptor (D–A) polymer, are produced by incorporating either an alkyl thiophene (PIDTT‐DFBT‐T) or alkyl thieno[3,2‐b]thiophene (PIDTT‐DFBT‐TT) π‐bridge as spacer. Although the PIDTT‐DFBT‐TT polymer exhibits decreased absorption at longer wavelengths and increased absorption at higher energy wavelengths, it shows higher power conversion efficiencies in devices. In contrast, the thiophene bridged PIDTT‐DFBT‐T shows a similar change in its absorption spectrum, but its low molecular weight leads to reduced hole mobilities and performance in photovoltaic cells. Inverted solar cells based on PIDTT‐DFBT‐TT are explored by modifying the electron‐transporting ZnO layer with a fullerene self‐assembled monolayer and the MoO3 hole‐transporting layer with graphene oxide. This leads to power conversion efficiencies as high as 7.3% in inverted cells. PIDTT‐DFBT‐TT's characteristic strong short wavelength absorption and high efficiency suggests it is a good candidate as a wide band gap material for tandem solar cells. 相似文献
14.
Mario Caironi Matt Bird Daniele Fazzi Zhihua Chen Riccardo Di Pietro Christopher Newman Antonio Facchetti Henning Sirringhaus 《Advanced functional materials》2011,21(17):3371-3381
Charge transport is investigated in high‐mobility n‐channel organic field‐effect transistors (OFETs) based on poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2), Polyera ActivInk? N2200) with variable‐temperature electrical measurements and charge‐modulation spectroscopy. Results indicate an unusually uniform energetic landscape of sites for charge‐carrier transport along the channel of the transistor as the main reason for the observed high‐electron mobility. Consistent with a lateral field‐independent transport at temperatures down to 10 K, the reorganization energy is proposed to play an important role in determining the activation energy for the mobility. Quantum chemical calculations, which show an efficient electronic coupling between adjacent units and a reorganization energy of a few hundred meV, are consistent with these findings. 相似文献
15.
Using Molecular Design to Increase Hole Transport: Backbone Fluorination in the Benchmark Material Poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]‐thiophene (pBTTT) 下载免费PDF全文
Pierre Boufflet Yang Han Zhuping Fei Neil D. Treat Ruipeng Li Detlef‐M. Smilgies Natalie Stingelin Thomas D. Anthopoulos Martin Heeney 《Advanced functional materials》2015,25(45):7038-7048
The synthesis of a novel 3,3′‐difluoro‐4,4′‐dihexadecyl‐2,2′‐bithiophene monomer and its copolymerization with thieno[3,2‐b]thiophene to afford the fluorinated analogue of the well‐known poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]‐thiophene) (PBTTT) polymer is reported. Fluorination is found to have a significant influence on the physical properties of the polymer, enhancing aggregation in solution and increasing melting point by over 100 °C compared to nonfluorinated polymer. On the basis of DFT calculations these observations are attributed to inter and intramolecular S…F interactions. As a consequence, the fluorinated polymer PFBTTT exhibits a fourfold increase in charge carrier mobility compared to the nonfluorinated polymer and excellent ambient stability for a nonencapsulated transistor device. 相似文献
16.
Yutaka Ie Masashi Nitani Makoto Karakawa Hirokazu Tada Yoshio Aso 《Advanced functional materials》2010,20(6):907-913
An electronegative conjugated compound composed of a newly designed carbonyl‐bridged bithiazole unit and trifluoroacetyl terminal groups is synthesized as a candidate for air‐stable n‐type organic field‐effect transistor (OFET) materials. Cyclic voltammetry measurements reveal that carbonyl‐bridging contributes both to lowering the lowest unoccupied molecular orbital energy level and to stabilizing the anionic species. X‐ray crystallographic analysis of the compound shows a planar molecular geometry and a dense molecular packing, which is advantageous to electron transport. Through these appropriate electrochemical properties and structures for n‐type semiconductor materials, OFET devices based on this compound show electron mobilities as high as 0.06 cm2 V?1 s?1 with on/off ratios of 106 and threshold voltages of 20 V under vacuum conditions. Furthermore, these devices show the same order of electron mobility under ambient conditions. 相似文献
17.
Kammasandra Nanjunda Shivananda Irit Cohen Elena Borzin Yulia Gerchikov Michal Firstenberg Olga Solomeshch Nir Tessler Yoav Eichen 《Advanced functional materials》2012,22(7):1489-1501
Sequence‐independent or “click” chemistry is applied for the preparation of a series of novel and structurally similar π‐conjugated oligomers. The new oligomers are prepared using Wittig–Horner chemistry from bifunctional building blocks that can be interconnected to one another at any desired sequence. The bifunctional building blocks consist of aromatic skeletons with acetal protected aldehyde groups on one side and a phosphonic acid diethyl ester group para to the aldehyde functionality. The first step in the arylenevinylene formation is a Wittig–Horner coupling of a functionalized aldehyde with the methyl phosphonate ester ylide of a bifunctional monomer. A stepwise protection–deprotection process is applied for the preparation of structurally similar π‐conjugated oligo‐phenylene vinylenes. New di‐, tri‐, penta‐, and hepta‐phenylenevinylenes are prepared and characterized. Selected penta‐arylenevinylenes are incorporated as the semiconductor channel in organic field‐effect transistors. 相似文献
18.
N. Drolet J.‐F. Morin N. Leclerc S. Wakim Y. Tao M. Leclerc 《Advanced functional materials》2005,15(10):1671-1682
We have fabricated organic field‐effect transistors based on thin films of 2,7‐carbazole oligomeric semiconductors 1,4‐bis(vinylene‐(N‐hexyl‐2‐carbazole))phenylene (CPC), 1,4‐bis(vinylene‐(N′‐methyl‐7′‐hexyl‐2′‐carbazole))benzene (RCPCR), N‐hexyl‐2,7‐bis(vinylene‐(N‐hexyl‐2‐carbazole))carbazole (CCC), and N‐methyl‐2,7‐bis(vinylene‐(7‐hexyl‐N‐methyl‐2‐carbazole))carbazole (RCCCR). The organic semiconductors are deposited by thermal evaporation on bare and chemically modified silicon dioxide surfaces (SiO2/Si) held at different temperatures varying from 25 to 200 °C during deposition. The resulting thin films have been characterized using UV‐vis and Fourier‐transform infrared spectroscopies, scanning electron microscopy, and X‐ray diffraction, and the observed top‐contact transistor performances have been correlated with thin‐film properties. We found that these new π‐conjugated oligomers can form highly ordered structures and reach high hole mobilities. Devices using CPC as the active semiconductor have exhibited mobilities as high as 0.3 cm2 V–1 s–1 with on/off current ratios of up to 107. These features make CPC and 2,7‐carbazolenevinylene‐based oligomers attractive candidates for device applications. 相似文献
19.
A.J.J.M. vanBreemen P.T. Herwig C.H.T. Chlon J. Sweelssen H.F.M. Schoo E.M. Benito D.M. deLeeuw C. Tanase J. Wildeman P.W.M. Blom 《Advanced functional materials》2005,15(5):872-876
The influence of the substitution pattern (unsymmetrical or symmetrical), the nature of the side chain (linear or branched), and the processing of several solution processable alkoxy‐substituted poly(p‐phenylene vinylene)s (PPVs) on the charge‐carrier mobility in organic field‐effect transistors (OFETs) is investigated. We have found the highest mobilities in a class of symmetrically substituted PPVs with linear alkyl chains (e.g., R1, R2 = n‐C11H23, R3 = n‐C18H37). We have shown that the mobility of these PPVs can be improved significantly up to values of 10–2 cm2 V–1 s–1 by annealing at 110 °C. In addition, these devices display an excellent stability in air and dark conditions. No change in the electrical performance is observed, even after storage for thirty days in humid air. 相似文献