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A highly fluorinated alternating polymer, P(RFMi-St), possessing improved thermal properties and patterning capabilities over perfluoroalkyl polymethacrylates under high energy radiation was achieved with semi-perfluorododecyl maleimide (RFMi) and styrene (St). RFMi could be synthesised efficiently via a Mitsunobu reaction condition and copolymerised with St by free radical and reversible-deactivation radical polymerisation protocols. P(RFMi-St) showed a satisfactory glass-transition temperature (108 °C) and intermolecular cross-linking behaviour under electron-beam and commercially more important extreme UV (λ = 13.5 nm) irradiation. The exposed regions lost their solubility, resulting in the successful formation of mechanically non-deteriorated negative-tone images down to 50 nm. In addition, P(RFMi-St) could be solution-processed with chemically non-damaging fluorous liquids, which enabled the polymer to be applied effectively on top of an organic semiconductor layer as a dielectric material (dielectric constant 2.7) for the organic field-effect transistor fabrication.

High-mobility low-hysteresis electrolyte-gated thin-film transistors were successfully fabricated using a diketopyrrolopyrrole (DPP) and benzotriazole (BTz) copolymer semiconductor and high-capacitance ion gels based on 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([EMI][TFSI]) and tetraoctyl phosphonium ([P8888]) [TFSI]. The DPP-BTz transistors gated with both ion gels operated effectively at low voltages below 1V with high on-to-off current ratios exceeding 105 and very low device hysteresis. Specifically, when the [EMI][TFSI] ion gel was employed as a gate dielectric layer, the DPP-BTz transistors exhibited a very high carrier-mobility value of 8.50 ± 1.09 cm2/Vs. In addition, device hysteresis of the DPP-BTz transistor was almost invariant to the voltage sweeping rate and was much lower than that of the poly(3-hexylthiophene) (P3HT) transistor under the same conditions. Overall, these results indicate that the performance of electrolyte-gated transistors can be improved using the DPP-BTz semiconductor.

The multiscale morphology and device performance of printed semiconducting polymers are highly sensitive to the substrate/ink interfacial properties during solution coating. There is an urgent need for general design rules correlating the substrate properties and conjugated polymer (CP) morphology, which do not yet exist. Dynamic surfaces are particularly promising for templating highly crystalline and highly aligned conjugated polymer thin films and have been shown in recent studies. Herein, we implement the dynamic-templating method using a series of liquid-infused nanoporous substrates as a tool to study the impact of template reconfigurability and chemistry on the multiscale morphology of conjugated polymer thin films, using a high performing donor–acceptor polymer (DPP-BTz) as a model compound. By quantifying the enthalpy of adsorption, we demonstrate that the strength of template–CP interactions directly measures the effectiveness of dynamic surfaces in promoting conjugated polymer crystallization and alignment. We further show that the enthalpy of interactions increases by enhancing the template dynamics and is sensitively modulated by template chemistry. Specifically, increasing the template–CP interactions leads to a larger domain size and higher degree of crystallinity in templated conjugated polymer thin films prepared by meniscus-guided solution coating. This observation validates our hypothesis that dynamic templates function by promoting the nucleation of conjugated polymers. We also demonstrate that such dynamic-template-dependent morphology is independent of coating speed. Notably, the enhanced morphological properties modulate the charge carrier mobility in field-effect transistors (FETs) over an order of magnitude reaching a hole mobility of 2.8 cm2 V−1 s−1. This work is a significant step towards establishing general guidelines on how the substrate–ink interfacial properties influence morphology and performance of solution coated CP thin films.

Dynamic surfaces play a critical role in templating highly ordered complex structures in living systems but are rarely employed for directing assembly of synthetic functional materials. We design ion gel templates with widely tunable dynamics ( Tg) to template solution-coated conjugated polymers. We hypothesize that the ion gel expedites polymer nucleation by reconfiguring its surface to facilitate cooperative multivalent interactions with the conjugated polymer, validated using both experimental and computational approaches. Varying ion gel dynamics enables large modulation of alignment, molecular orientation, and crystallinity in templated polymer thin films. At the optimal conditions, ion-gel-templated films exhibit 55 times higher dichroic ratio (grazing incidence X-ray diffraction) and 49% increase in the relative degree of crystallinity compared to those templated by the neat polymer matrix. As a result, the maximum hole mobilities increase by factors of 4 and 11 along the π-π stacking and the backbone directions. Intriguingly, we observe a synergistic effect between the gel matrix and the ionic liquid that produces markedly enhanced templating effect than either component alone. Molecular dynamics simulations suggest that complementary multivalent interactions facilitated by template reconfigurability underlie the observed synergy. We further demonstrate field-effect transistors both templated and gated by ion gels with average mobility exceeding 7 cm2 V-1 s-1.

We report the formation of robust, reproducible, pinhole-free, thin layers of fluorinated polyfluorene conjugated copolymers on a range of polymeric underlayers via a simple solution processing method. This is driven by the different characters of the fluorinated and nonfluorinated sections of these polymers. Photothermal deflection spectroscopy is used to determine that these layers are 1-2 nm thick, corresponding to a molecularly thin layer. Evidence that these layers are continuous and pinhole-free is provided by electroluminescence data from polymer LED devices that incorporate these layers within the stacked LED structure. These reveal, remarkably, light emission solely from these molecularly thin layers.

Ambipolar organic field-effect transistors (OFETs) have both of hole and electron enhancements in charge transport. The characteristics of conjugated diketopyrrolopyrrole ambipolar OFETs depend on the metal-contact surface treatment for charge injection. To investigate the charge-injection characteristics of ambipolar transistors, these devices are processed via various types of self-assembled monolayer treatments and annealing. We conclude that treatment by the self-assembled monolayer 1-decanethiol gives the best enhancement of electron charge injection at both 100 and 300 °C annealing temperature. In addition, the contact resistance is calculated by using two methods: One is the gated four-point probe (gFPP) method that gives the voltage drop between channels, and the other is the simultaneous contact resistance extraction method, which extracts the contact resistance from the general transfer curve. We confirm that the gFPP method and the simultaneous extraction method give similar contact resistance, which means that we can extract contact resistance from the general transfer curve without any special contact pattern. Based on these characteristics of ambipolar p- and n-type transistors, we fabricate inverter devices with only one active layer.

Dynamic-template-directed assembly is a promising method to enhance molecular ordering and electronic properties of solution-coated polymer semiconductor thin films over a large area. In this work, we establish that multicomponent dynamic templates of complementary chemistries can promote polymer crystallization through cooperative multivalent interactions. We investigate this phenomenon using a combination of templating substrates including a fluoropolymer, a hydrogen-bonded liquid, and an ionic liquid (IL). Template-dependent multiscale morphology is studied by a comprehensive set of characterization techniques to understand how introducing diverse chemical moieties modulates polymer assembly. Our results clearly confirm synergistic effects between components of complementary chemistries constituting the dynamic template. The relative degree of crystallinity is improved by 50-150% for films deposited on multicomponent dynamic templates compared to their neat constituents. In addition, macroscopic alignment is increased significantly (2-5 times) compared to single-component templates. As a result, highly anisotropic charge transport is observed with apparent hole mobilities up to 3.6 cm2 V-1 s-1. In contrast, such a synergistic effect is not observed when using a multicomponent dynamic template of comparable chemistries (i.e., IL and polymerized IL). We elucidate the origin of this synergistic effect by using attenuated total reflectance Fourier transform infrared spectroscopy and isothermal titration calorimetry. When the dynamic template comprises two or more components interacting with complementary binding sites on the conjugated polymer (CP) (esp. backbone vs side chain), the template-polymer interactions is significantly enhanced compared to the sum of single component contributions. These results provide valuable insights into surface-directed CP crystallization during large-area solution coating. Template dynamics is rarely studied and represents a new opportunity for guiding assembly of soft functional matter.

Printing flow planarizes conjugated polymers and alters assembly pathways to substantially enhance electronic properties., Intrachain charge transport is unique to conjugated polymers distinct from inorganic and small molecular semiconductors and is key to achieving high-performance organic electronics. Polymer backbone planarity and thin film morphology sensitively modulate intrachain charge transport. However, simple, generic nonsynthetic approaches for tuning backbone planarity and the ensuing multiscale assembly process do not exist. We first demonstrate that printing flow is capable of planarizing the originally twisted polymer backbone to substantially increase the conjugation length. This conformation change leads to a marked morphological transition from chiral, twinned domains to achiral, highly aligned morphology, hence a fourfold increase in charge carrier mobilities. We found a surprising mechanism that flow extinguishes a lyotropic twist-bend mesophase upon backbone planarization, leading to the observed morphology and electronic structure transitions.

Extreme ultraviolet (EUV) lithography, using 13.5 nm radiations, is almost ready for high volume manufacturing. EUV lithography is expected to be the main technology for manufacturing leading-edge devices and continuous improvement of lithography performance is still needed. We have developed several metal oxide containing resists and recently focused on metal organic cluster photoresists with controlled size distribution. In this paper, material properties and lithography performance of our new metal organic cluster photoresists are discussed.

We propose a concept of organic small molecule-based EUV resists that do not require sub-stoichiometric ingredients. Based on our previous results with highly fluorinated electron-beam (e-beam) resists, we designed amorphous small molecules equipped with perfluoroalkyl ether (PFAE) chains. The synthesis of the prototype was carried out successfully, and its physical properties, imaging mechanism, and performance were all evaluated under e-beam exposure conditions. Although the prototype showed slightly low sensitivity to EUV irradiation, we were able to mitigate the issue by appending other cross-linkable functional moieties. The modified version showed decent negative-tone patterning performance under e-beam exposure and could form images under EUV irradiation and the pattern development step using highly fluorinated solvents.

Extreme ultraviolet (EUV) lithography, using 13.5 nm radiation, is a prominent candidate for next generation manufacturing. Our main effort has recently focused on metal organic cluster photoresists, including both Zr and Hf metal oxides, both relatively low EUV absorbing metals. However, integration of high EUV absorption elements is now considered to be a more promising route to further improve lithographic performance under EUV radiation. Here, we report lithography of zinc oxide-based metal organic cluster photoresists, and EUV patterning below 15 nm. The lithographic performance of this and other metal oxides is described and etch characteristics discussed.

Nanostructured carbon materials have outstanding physical properties and high aspect ratios. They have attracted much attention for use as polymer composite reinforcements. In this study, alkylated and reduced graphene oxide nanoribbons (A-rGONRs) were prepared by unzipping multi-walled carbon nanotubes (MWCNTs), followed by a simple alkylation/chemical reduction process using a Dean-Stark trap. A-rGONRs have morphologies with width 30–50 nm and lengths of several micrometers (aspect ratio >100). They are similar to one-dimensional MWCNTs, but with extended interfacial areas and edge functional sites. Approximately 25 wt% of the alkyl chains were chemically introduced onto the surface of A-rGONRs, which gave rise to hydrophobic properties and a surface energy of 23.8 mJ m−2. A stable A-rGONRs suspension was achieved in xylene even after 24 h. Through a wet process, A-rGONRs were homogeneously dispersed in an isotactic polypropylene (iPP) host. iPP/A-rGONRs nanocomposites showed significant enhancements in thermal and mechanical properties when compared to pure iPP.

We present the integration of flexible and microscale organic nonvolatile resistive memory devices fabricated in a cross-bar array structure on plastic substrates. This microscale integration was made via orthogonal photolithography method using fluorinated photoresist and solvents and was achieved without causing damage to the underlying organic memory materials. Our flexible microscale organic devices exhibited high ON/OFF ratio (I(ON/I(OFF) > 10(4)) under bending conditions. In addition, the ON and OFF states of our flexible and microscale memory devices were maintained for 10,000 seconds without any serious degradation.

Display Omitted The patterning method of MWCNT is defined by PFDMA mask in a lift-off process.Finely defined lines were observed at the edge of the patterned MWCNT films.PEDOT:PSS, a conducting polymer, does not react with the patterned PFDMA.MWCNT/PEDOT:PSS films were improved the sheet resistance compared to MWCNT films.The optimal coating volume of MWCNT/PEDOT:PSS was examined to achieve fine patterns. This paper reports a micro patterning method for multi-walled carbon nanotubes (MWCNTs), whose patterns were defined by a poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (PFDMA) mask in a lift-off process. The PFDMA layer on the patterned polydimethylsiloxane (PDMS) mold was transferred to a polyethylene naphthalate (PEN) film using a Micro-Contact Printing (µCP) technique. In contrast to conventional photoresist masks, the PFDMA polymer template was not damaged by the solvent used for the MWCNT dispersion, isopropyl alcohol (IPA), which enabled the precise and clean deposition of MWCNTs. Moreover, a hydrofluoroether solvent, which was used to remove the PFDMA template, did not show any signal for chemical interactions with the PEN substrate or poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). This orthogonal character led to the successful lift-off patterning of MWCNTs/PEDOT:PSS composite films. The micro-patterned composite films could be examined further as a thin film heater with a bending radius of 15mm, generating enough heat to reach a maximum temperature of 53?C with an applied voltage of 30V.

Organic and polymeric electroluminescent (EL) devices working under alternating current (AC) electricity have drawn technological attention due to their light‐emitting principles and have great potential for applications. In spite of recent advances in AC EL devices, mechanically robust, patternable full‐color emission layers with high brightness have rarely been demonstrated. In this manuscript, we report high‐performance full‐color AC EL devices with nonradiating polymers solution blended in fluorescent polymer emissive layers. Conventional nonradiating polymers such as poly(styrene) (PS) and poly(α‐methyl styrene) in an emissive layer enhanced the brightness of individual red (R), green (G), and blue (B) colors to several thousand cd m⁻². Systematic investigation revealed bi‐functional roles of PS not only as a diluting agent but also as an electron capturer. This resulted in the hole and electron carriers being balanced in the emissive layer, leading to improved power and current efficiency. Furthermore, our blended emission film consisting of 83 vol % PS is mechanically robust with excellent surface adhesion as well as uniformity, when combined with scratch‐tolerant AC device architecture, not only resulted in large area cell operation but also allowed for a solution‐based pattern‐mask process, giving rise to well‐defined R, G, and B cells individually addressable in a single device platform. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1629–1640

In this study, vertically stacked microscale organic resistive nonvolatile memory devices are demonstrated. The fabricated devices consisted of vertically stacked two layers of 32 × 32 crossbar-structured organic memory devices (total of 2048 memory cells) with a memory-cell size of 7 × 7 μm2 on a SiO2 substrate. The microscale organic memory devices were made using an orthogonal photolithography technique with a highly fluorinated photoresist and development solvent. The vertically stacked microscale organic memory devices showed reproducibility with good endurance, and stability and long retention times (over 104 s) for both layers. The realization of vertical stacking of microscale organic memory devices might enable the production of organic memory devices toward the three-dimensional integration of organic electronic devices.

We demonstrated 4K-bit microscale organic nonvolatile resistive memory devices fabricated with a 10 × 10 μm2 cell size in a 64 × 64 cross-bar array structure. This microscale integration was made via orthogonal photolithography processes using fluorinated photoresist and solvents and was achieved without causing damage to the underlying organic memory materials. Our microscale organic devices exhibited excellent memory performance that was retained more than 10 days with a high ON/OFF ratio (>107) and good endurance switching characteristics (>300 cycles). The demonstration of 4K-bit organic memory devices promises a possibility of highly-integrated microscale organic electronics applications.

This communication reports a materials handling strategy based on fluorous materials chemistry using CdSe/CdS/CdZnS core–shell type semiconductor nanocrystals. When the crystals were treated with the semi-perfluoroalkanethiol ligands in the presence of iPr2EtN, the surface-modified nanocrystals (RF1-NC and RF2-NC) became soluble in the fluorous liquids. Solutions of RF1-NC and RF2-NC in HFE-7500 enabled the solution-casting of nanocrystalline films on top of a small-molecular hole-transporting layer and provided layered structures suitable for light-emitting diode fabrication.

We fabricated micro-scale organic field effect transistors (OFETs) and complementary inverters on a twistable polyimide (PI) substrate by applying orthogonal photolithography. By applying a highly fluorinated photoresist and development solvent, it becomes possible to create organic electronic devices with a micro-scale channel length without damaging the underlying polymer films. The 3 μm-channel twistable pentacene OFET devices and complementary inverters created using p-type pentacene and n-type copper hexadecafluorophthalocyanine exhibited stable electrical characteristics from flat to twist configurations (angle of up to ∼50°). The realization of twistable micro-scale OFETs and inverter devices on a PI substrate may enable the production of functioning organic devices in practical, flexible configurations.

Graphical abstractPoly 1H,1H,2H,2H-perfluorodecyl methacrylate (PFDMA) films are transfer-patterned onto various substrates by Micro-Contact Printing and embossing printing methods at room temperature. (1) Micro contact printing needs no pressure and (2) embossing is done under pressure for printing.Display Omitted Micro contact printing (µCP) was applied to prepare line and spacing structures.1H,1H,2H,2H-perfluorodecyl methacrylate (FDMA) can be a resist for µCP.The solubility of FDMA in fluorous solvents can achieve solvent orthogonality.The process of µCP can be done at room temperature without any external pressure. Micro-Contact Printing (µCP), one of the soft lithography techniques, has been widely used to fabricate patterns of various materials on inorganic or organic substrates because of its low process temperature and pressure. In this paper, using a poly(dimethylsiloxane) (PDMS) mold, poly(1H,1H,2H,2H-perfluorodecyl methacrylate) polymer (PFDMA) films is patterned and deposited on various substrates such as silicon wafer, silicon oxide on silicon wafer, glass, poly(methylmethacrylate) (PMMA), and poly (vinyl pyrrolidone) (PVP). Because of the soft nature of PFDMA containing HFE-7500 as a casting solvent, the µCP can be done at room temperature without surface treatment or external pressure. The driving force of µCP of PFDMA is the very low adhesion force of 0.52mN/m between PFDMA film and PDMS mold compared to those between PFDMA and the substrate materials. For surface energy estimation of PFDMA contact angle measurements are performed and the adhesion forces among various materials are calculated. It can be shown that the solubility of PFDMA in fluorine-containing solvents can settle down the solvent orthogonality problem. A complementary image can be formed by the subsequent embossing of the remaining PFDMA layers in the recess areas of the hard PDMS mold after the µCP processing. Lift-off deposition of Cr lines is demonstrated using the PFDMA polymer structure.

Electroluminescent (EL) devices operating at alternating current (AC) electricity have been of great interest due to not only their unique light emitting mechanism of carrier generation and recombination but also their great potential for applications in displays, sensors, and lighting. Despite great success of AC-EL devices, most device properties are far from real implementation. In particular, the current state-of-the art brightness of the solution-processed AC-EL devices is a few hundred candela per square meter (cd m(-2)) and most of the works have been devoted to red and white emission. In this manuscript, we report extremely bright full color polymer AC-EL devices with brightness of approximately 2300, 6000, and 5000 cd m(-2) for blue (B), green (G), and red (R) emission, respectively. The high brightness of blue emission was attributed to individually networked multiwalled carbon nanotubes (MWNTs) for the facile carrier injection as well as self-assembled block copolymer micelles for suppression of interchain nonradiative energy quenching. In addition, effective FRET from a solution-blended thin film of B-G and B-G-R fluorescent polymers led to very bright green and red EL under AC voltage, respectively. The solution-processed AC-EL device also worked properly with vacuum-free Ag paste on a mechanically flexible polymer substrate. Finally, we successfully demonstrated the long-term operation reliability of our AC-EL device for over 15 h.

In this article we discuss the synthesis of four new low band-gap co-polymers based on the diketopyrrolopyrrole (DPP) and benzotriazole (BTZ) monomer unit. We demonstrate that the BTZ unit allows for additional solubilizing side-chains on the co-monomer and show that the introduction of a linear side-chain on the DPP-unit leads to an increase in thin-film order and charge-carrier mobility if a sufficiently solubilizing, branched, side chain is attached to the BTZ. We compare two different synthetic routes, direct arylation and Suzuki-polycondensation, by a direct comparison of polymers obtained via the two routes and show that direct arylation produces polymers with lower electrical performance which we attribute to a higher density of chain Furthermore we demonstrate that a polymer utilizing this design motif and synthesized via Suzuki-polycondensation ((l-C-18)-DPP-(b-C-17)-BTZ) exhibits exceptionally high and near balanced average electron and hole mobilities > 2 cm(2) V-1 s(-1) which are among the highest, robustly extracted mobility values reported for DPP copolymers in a top-gate configuration to date. Our results demonstrate clearly that linear side chain substitution of the DPP unit together with co-monomers that allow for the use of sufficiently long or branched solubilizing side chains can be an attractive design motif for solution processable, high mobility DPP copolymers.

A combined soft lithographic transfer-printing and patterning method of highly fluorinated polymers was investigated aiming to establish a facile surface treatment protocol for various substrates. Spin-coated layers of poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (PFDMA) on patterned polydimethylsiloxane (PDMS) molds were transfer-printed successfully on silicon, glass, aluminum substrates, resulting in the well-controlled production of nano to micrometer-scale periodic structures. With careful optimization of the dimension and density of the PFDMA patterns, it was possible to achieve a water contact angle as high as 175° on the transfer-printed highly fluorinated polymer film. One of the advantages of the transfer-patterning method is that highly fluorinated polymer films can be printed on curved surfaces while retaining their superhydrophobic and corrosion-prevention character. In addition, the transfer-printed PFDMA layers on the glass plates showed enhanced light transmission, which led to the extraction of 10% more light when they were applied to the emitting side of green organic light-emitting devices. The micro-patterned PFDMA surfaces also exhibited a significantly reduced level of bacterial adhesion when they were incubated in human bile juice. These results strongly suggest that the proposed facile transfer-patterning protocol of highly fluorinated polymer films can be a suitable surface-treatment technique for implantable electronic devices that exhibit improved device performance and anti-biofouling nature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45184.

A semiconducting polymers with conjugated diketopyrrolopyrrole (DPP) unit was developed for high performance ambipolar organic field-effect transistors (OFETs). We report electrical characteristics of DPP OFETs in various ways which measured transistor and inverter performance with various bias conditions and self-assembled monolayers (SAMs) treatment. Ambipolar DPP conjugated polymer OFETs showed high hole and electron mobility of μh=0.57 cm2V-1s-1 and μe=0.51 cm2V-1s-1 with O2 plasma treatment and 1-decanethiol SAMs treatment, respectively with annealing at 100°C. Contact resistance effect on mobilities was investigated by measuring contact resistance during device operation through gated four-point probe (gFPP) and simultaneous contact resistance extraction model directly from current voltage characteristics.

Charge transport in conjugated polymer semiconductors has traditionally been thought to be limited to a low-mobility regime by pronounced energetic disorder. Much progress has recently been made in advancing carrier mobilities in field-effect transistors through developing low-disorder conjugated polymers. However, in diodes these polymers have to date not shown much improved mobilities, presumably reflecting the fact that in diodes lower carrier concentrations are available to fill up residual tail states in the density of states. Here, we show that the bulk charge transport in low-disorder polymers is limited by water-induced trap states and that their concentration can be dramatically reduced through incorporating small molecular additives into the polymer film. Upon incorporation of the additives we achieve space-charge limited current characteristics that resemble molecular single crystals such as rubrene with high, trap-free SCLC mobilities up to 0.2 cm2/Vs and a width of the residual tail state distribution comparable to kBT., Charge transport in organic diodes based on conjugated polymers is severely limited by the high water-related trap concentration and energetic disorder. Here, the authors report high-mobility trap-free charge transport in low-disorder conjugated polymers by incorporating small molecular additives.