Organic Vapor Jet Printing Research Articles

Steven V. Abramson: An OLED Unicorn Setting a Shining Example for the Industry

Steven V. Abramson: An OLED Unicorn Setting a Shining Example for the Industry

Printable Organic Electronic Materials for Precisely Positioned Cell Attachment.

Over the past 3 decades, there has been a vast expansion of research in both tissue engineering and organic electronics. Although the two fields have interacted little, the materials and fabrication technologies which have accompanied the rise of organic electronics offer the potential for innovation and translation if appropriately adapted to pattern biological materials for tissue engineering. In this work, we use two organic electronic materials as adhesion points on a biocompatible poly(p-xylylene) surface. The organic electronic materials are precisely deposited via vacuum thermal evaporation and organic vapor jet printing, the proven, scalable processes used in the manufacture of organic electronic devices. The small molecular-weight organics prevent the subsequent growth of antifouling polyethylene glycol methacrylate polymer brushes that grow within the interstices between the molecular patches, rendering these background areas both protein and cell resistant. Last, fibronectin attaches to the molecular patches, allowing for the selective adhesion of fibroblasts. The process is simple, reproducible, and promotes a high yield of cell attachment to the targeted sites, demonstrating that biocompatible organic small-molecule materials can pattern cells at the microscale, utilizing techniques widely used in electronic device fabrication.

Organic Vapor Jet Printing: Organic Vapor‐Jet Printing with Reduced Heat Transfer for Fabrication of Flexible Organic Devices (Adv. Mater. Technol. 2/2019)

Organic Vapor Jet Printing: Organic Vapor‐Jet Printing with Reduced Heat Transfer for Fabrication of Flexible Organic Devices (Adv. Mater. Technol. 2/2019)

Printing of small molecular medicines from the vapor phase

There is growing need to develop efficient methods for early-stage drug discovery, continuous manufacturing of drug delivery vehicles, and ultra-precise dosing of high potency drugs. Here we demonstrate the use of solvent-free organic vapor jet printing to deposit nanostructured films of small molecular pharmaceutical ingredients, including caffeine, paracetamol, ibuprofen, tamoxifen, BAY 11-7082 and fluorescein, with accuracy on the scale of micrograms per square centimeter, onto glass, Tegaderm, Listerine tabs, and stainless steel microneedles. The printed films exhibit similar crystallographic order and chemistry as the original powders; controlled, order-of-magnitude enhancements of dissolution rate are observed relative to powder-form particles. In vitro treatment of breast and ovarian cancer cell cultures in aqueous media by tamoxifen and BAY 11-7082 films shows similar behavior to drugs pre-dissolved in dimethyl sulfoxide. The demonstrated precise printing of medicines as films, without the use of solvents, can accelerate drug screening and enable continuous manufacturing, while enhancing dosage accuracy.

10‐3: Invited Paper: Organic Vapor Jet Printing, a Solvent‐Less, Mask‐Less Patterning Technology for OLED Displays

Organic Vapor Jet Printing (OVJP) is a solvent‐less, mask‐less printing technology for depositing patterned small molecule organic materials to manufacture large area side by side R‐G‐B OLED displays. This paper discusses a brief history of OVJP, describes recent technology advances and describes prospects for large area mass production systems.

Organic vapor-jet-based route for solvent-free additive formation of oxide semiconductors

We demonstrate a novel solution-free technique which can be used to print metal oxide patterns without masks by adopting an organic vapor jet printing (VJP) method. To avoid the high deposition temperatures required for metal oxide vaporization, metal-organic compounds are first jet-printed as metal-oxide precursors and converted into metal oxides by a photo-conversion process. As an example, we show that indium oxides can easily be prepared from jet-printed films of indium acetylacetonate upon photo-conversion; the effectiveness of which is supported by X-ray photoelectron spectroscopy (XPS) showing a reduction of the carbon portion associated with the alkyl chains of the precursors. A carrier mobility of 4.5 cm2/V·s and an on/off ratio of 105 are demonstrated in the oxide thin-film transistors based on indium oxides prepared by the proposed method, illustrating the potential usefulness of this process in electronic device fabrication.

Spatial Mapping of Morphology and Electronic Properties of Air‐Printed Pentacene Thin Films

To accelerate the pace of materials discovery and application, comprehensive links need to be established between a material's structure, properties, and process conditions used to obtain the material and/or final application format. This work examines the dry printing of pentacene thin film transistor (TFT) channels by guard flow‐enhanced organic vapor jet printing (GF‐OVJP), a technique that enables direct, solvent‐free, additive patterning of device‐quality molecular semiconductors in air. Deposition in air entails non‐trivial effects at the boundary between ambient surroundings and the gas jet carrying the semiconductor vapor that influence the morphology and properties of the resulting electronic devices. Synchrotron X‐ray diffraction is employed, complemented by measurement of electronic properties of GF‐OVJP deposited films in a TFT to reveal how the morphology and electronic properties of the films depend on thickness, location within the printed pattern, nozzle translation velocity, and other process parameters. The hole field‐effect mobility of the printed pentacene film is linked quantitatively with its crystallinity, as well as with extent of exposure to ambient air during deposition. The analysis can be extended to accurately predict the performance of devices deposited in air by GF‐OVJP, which are demonstrated here for a planar, large area deposit.

Thin-Film Growth and Patterning Techniques for Small Molecular Organic Compounds Used in Optoelectronic Device Applications

Rapid advances in research and development in organic electronics have resulted in many exciting discoveries and applications, including organic light-emitting devices for information display and illumination, solar cells, photodetectors, chemosensors, and logic. Organic optoelectronic materials are broadly classified as polymeric or small molecular. For the latter category, solvent-free deposition techniques are generally preferred to form well-defined interfaces and improve device performance. This article reviews several deposition and patterning methods for small molecular thin films and devices, including organic molecular beam deposition, vacuum thermal evaporation, organic vapor phase deposition, and organic vapor jet printing, and compares them to several other methods that have been proposed recently. We hope this review provides a compact but informative summary of the state of the art in organic device processing and addresses the various techniques' governing physical principles.

Vapor‐Phase Microprinting of Multicolor Phosphorescent Organic Light Emitting Device Arrays

Multicolor electrophosphorescent organic light-emitting diode (OLED) pixel patterning by organic vapor jet printing (OVJP) is demonstrated, showing that this technique is capable of rapidly generating high-definition full-color displays. The resolution limits, and means to achieve them are described using a combination of simulation and experimental approaches.

Guard flow-enhanced organic vapor jet printing of photovoltaic donor materials in air

We demonstrate the ability to rapidly deposit (local deposition rates well exceeding 1000Å/s) in air a small molecular electron donor material boron subphthalocyanine chloride (SubPc) for use in photovoltaic devices. The method employs a highly collimated jet of hot nitrogen gas carrying organic vapor toward a substrate, on which the organic molecules condense. A secondary jet of nitrogen coaxially surrounds the primary jet, shielding the organic vapor from the atmosphere. We study how the guard flow rate affects the printed film morphology and the resulting device properties. Notably, the crystallinity of the donor film can be increased while lowering the thin-film roughness, enhancing short circuit photocurrent nearly twofold over films printed without guard flow, allowing the photovoltaic power conversion efficiency of planar heterojunction SubPc/C60 cells to exceed 2% with SubPc deposited at ambient conditions.

Digital‐Mode Organic Vapor‐Jet Printing (D‐OVJP): Advanced Jet‐on‐Demand Control of Organic Thin‐Film Deposition

Digital-mode organic vapor-jet printing (D-OVJP) is demonstrated by producing a series of organic vapor jets. D-OVJP not only inherits all the benefits of a conventional OVJP but also provides an advanced, straightforward control over organic deposition with a pixel-to-pixel precision. Digitally-controlled film thickness and high-performance thin-film transistors are demonstrated with D-OVJP, proving its potential applicability to organic electronics and related areas.

Fluid dynamics and mass transport in organic vapor jet printing

Organic vapor jet printing (OVJP) is a high-resolution mask and solvent-free organic thin film deposition and patterning technique. In this work, we analyze factors that affect the material deposition rate and the dynamics of gas flow through an OVJP print head consisting of an array of micron-sized nozzles. Scaling laws governing carrier gas flow dynamics through a system of microchannels and nozzles are developed. From these laws, we predict the deposition rate and doping ratio of organic material as a function of carrier gas flow. The analysis is applied to an experimental print head, and is compared to results obtained via a more complex, direct simulation Monte Carlo model. The print head is used to grow efficient green phosphorescent organic light emitting diodes having an external quantum efficiency and luminance comparable to analogous devices grown by vacuum thermal evaporation.

Effect of carrier gas temperature on pentacene thin film formation by organic vapor-jet printing techniques

Organic vapor jet printing (OVJP) is a powerful mask-free continuous method of fabricating organic thin film semiconductor devices. In the technique, vaporized organic compounds are carried by an inert carrier gas and jet-sprayed onto a substrate through a nozzle. During the printing process, the carrier gas temperature is controlled by an outer temperature control system. The morphology and electrical properties of organic thin films fabricated in this way can vary depending on the carrier gas temperature. This paper examines the effects of carrier gas temperature on OVJP systems. Pentacene thin films were fabricated, and their properties were compared with predicted behavior based on numerical simulations. Carrier gas temperatures exceeding 413K yielded bulk-mode pentacene thin films with high electrical mobilities. The temperature of the carrier gas was a significant factor in determining behavior and properties of the film.

High-Performance Pentacene Thin-Film Transistors Fabricated by Printing Technology

A high-performance bottom-contact pentacene thin-film transistor (TFT) is realized with its channel and electrodes fabricated by a simple printing process. By applying reverse offset printing of a nanosilver paste ink to the source/drain electrodes and organic vapor-jet printing to the thin pentacene layer, TFTs with a channel length of 20 μm are realized in a precise yet relatively simple fashion. The oxide formed during the processing of the silver ink is shown to help reduce the injection barrier between the source and pentacene, making it possible to realize high-performance bottom-contact TFTs without special treatment for the electrodes.

Organic vapor jet printing at micrometer resolution using microfluidic nozzle arrays

Organic vapor jet printing with a print head comprised of a microfluidic Si nozzle array is used to deposit parallel lines of an organic semiconductor thin film with a line width of 16 μm and edge resolution of 4 μm. Line width and feature size are functions of process conditions, depending strongly on nozzle-to-substrate separation distance. Experimental results are accurately characterized by a direct simulation Monte Carlo model. The model suggests that feature sizes of <1.5 μm are attainable by this printing process. The ability of the print head to codeposit doped films is demonstrated by growing the emissive layer of a green phosphorescent organic light emitting diode sandwiched between hole and electron transport layers deposited by vacuum thermal evaporation. This device had an external quantum efficiency of 8.8±1.3%, comparable to a similar device entirely grown by vacuum thermal evaporation.

High-Performance Pentacene Thin-Film Transistors Fabricated by Organic Vapor-Jet Printing

Organic vapor-jet printing, a maskless direct printing method, is used to fabricate high-performance pentacene thin-film transistors. By combining the optimal carrier gas temperature and the surface treatment of gate dielectrics, a mobility of 0.46 (±0.03) cm2 V-1 s-1 and an on-off ratio greater than 107 are achieved. Morphological analyses indicate that the relatively high carrier gas temperature and low surface energy of the dielectric surface are the keys in achieving the level of performance comparable to that of devices based on conventional technologies.

Direct vapor jet printing of three color segment organic light emitting devices for white light illumination

Organic-vapor jet printing (OVJP) is used to directly pattern small molecular weight electrophosphorescent white organic light-emitting devices (WOLEDs) consisting of parallel stripes of separate red, green, and blue OLEDs. The spatial patterning of the WOLEDs with peak forward viewing external quantum and luminous efficiencies of 7.1±0.3% and 7.0±0.4lm∕W, respectively, is accomplished by transporting the vapors of organic semiconductors through a nozzle to a translating sample substrate. Using multiple color segments to generate white light allows for the individual optimization of each color, is continuously color tunable, and can be used to compensate for differential aging of the constituent dopants. The theory and experimental results of WOLED printing via OVJP are discussed.

Direct patterning of organic light-emitting devices by organic-vapor jet printing

We demonstrate small molecular weight, fluorescent organic light-emitting devices directly patterned by organic-vapor jet printing (OVJP). In OVJP, a hot inert carrier gas picks up a molecular organic vapor that expands when passed through a nozzle, resulting in physisorption of the molecules onto a cooled substrate. A (1cm)2 flat organic semiconductor thin film is achieved by sweeping the nozzle over the substrate to print closely spaced lines. Using an array of nozzles, multiple parallel stripes are simultaneously printed at a growth rate of 3.4Åcm2∕s. Organic heterostructure fluorescent-light-emitting devices consisting of a broad area hole transport layer, followed by a striped electron transport layer, both printed by OVJP, yield an external quantum efficiency of (0.84±0.03)%, which is comparable to that of similar devices deposited by vacuum thermal evaporation.

Direct mask-free patterning of molecular organic semiconductors using organic vapor jet printing

We demonstrate the solvent-free, high-resolution direct printing of molecular organic semiconductors for use in low cost optoelectronic applications. In this method, called organic vapor jet printing, hot inert carrier gas picks up the molecular organic vapor and expands it through a microscopic nozzle, resulting in physisorption of the molecules onto a cooled substrate. Pattern resolution and printing speed are determined by the nozzle shape, nozzle-to-substrate distance, downstream pressure, and molecular mass of the carrier gas. Quantitative models are developed using a combination of scaling analysis, direct simulation Monte Carlo modeling, and printing experiments. Pattern resolutions of up to 1000dpi and local deposition rates exceeding 2300Å∕s are achieved. Pentacene channel thin film transistors are printed at a local deposition rate of 700Å∕s at both low and atmospheric pressures, resulting in a field-effect mobility of 0.25cm2∕Vs and a current on/off ratio of 7×105 for devices grown at a background pressure of 0.24Torr. The high directionality of the molecular jets and well-defined shape of the deposits enables combinatorial printing of structures and devices, while affording considerable control over film morphology. The method is also readily applicable to document printing using solvent-free inks.

Direct, Mask‐ and Solvent‐Free Printing of Molecular Organic Semiconductors

Molecular organic semiconductors have been printed (see Figure and cover) using direct, mask- and solvent-free printing via microscopic sonic jets of hot nitrogen seeded with the vapor of the organic semiconductor. Ultrahigh deposition rates, pattern resolution of up to 1000 dpi, and a high-performance pentacene thin-film transistor (TFT) are demonstrated. The theory, simulation, and experiments of this new method—organic vapor jet printing—are discussed.