Printing Process Suitable for Reel-to-Reel Production of High-Performance Organic Transistors and Circuits

Abstract

The possibility of low cost consumer electronics (e.g. large emissive displays, electronic paper, smart cards, etc.) that can be fabricated easily on lightweight, flexible plastic substrates has fueled the development of organic conducting, semiconducting, and light-emitting materials.[1±6] Because appropriate compounds now exist for many types of devices, research has expanded to include patterning methods that can take advantage of the easy processability of these materials. Although a recently described photolithographic process produced impressive results, [7] there may be advantages (cost, flexibility in materials that can be patterned, etc.) in using less conventional, non-photolithographic methods. Several such techniques (e.g. ink-jet printing [8±10] or screen printing [11±13] ) now appear to be suitable for a range of fabrication tasks at scales larger than^35± 100 mm. While there is speculation that the resolution of some of these methods can be improved to^10 mm, there is no experimental evidence that any of them work reliably at scales of even^20 mm, a factor of two larger than the critical dimensions (typically transistor channel lengths) needed for realistic applications of known materials.To address this problem, we recently demonstrated a fabrication strategy that combined an emerging high resolution technique (micromolding in capillaries [14] ) for defining critical features and an established low resolution method (screen printing) for patterning other elements of the devices.[15] We used this approach to produce organic transistors with channel lengths (^2 mm) comfortably smaller than those required for most important applications. We are currently working to improve the speed and flexibility of this technique, and to explore other methods that combine and match new specialized techniques with existing ones to yield a system that can pattern, in a rapid, low cost fashion, conducting elements with a resolution of at least 5±10 mm, and dielectrics, semiconductors, conductors, and electroluminescent materials on scales of 30±100 mm.Here we describe microcontact printing [16] and an upside-down fabrication sequence as components of a potentially useful route for manufacturing organic electronic devices. In this approach, microcontact printing first patterns source and drain electrodes and the appropriate interconnections at a resolution of^1 mm; the remaining components of the device (i.e. semiconductor, interlayer dielectric, and gate electrodes) are then patterned on top of these electrodes using low resolution techniques. (In the more typical rightside-up sequence, formation of source/drain electrodes occurs on top of the dielectric and gate layers.) We believe that this new strategy has many characteristics necessary for the type of rapid, large volume reel-to-reel processing that is considered important for cost effectively exploiting organics in microelectronics. The fabrication begins with microcontact printing, a technique that uses elastomeric stamps and inks to print patterns of self-as...

Paper-like electronic displays: Large-area rubber-stamped plastic sheets of electronics and microencapsulated electrophoretic inks

“…A low-cost rubber stamping technique known as CP (7,8) and a lithographic procedure based on molds and microfluidic channels (9,10) are, to our knowledge, the only nonphotochemical approaches to patterning that have micrometer resolution and have been used to fabricate organic transistors. CP is a particularly promising method that has the potential for patterning large areas quickly.…”

“…It was first described by Whitesides and Kumar (7) and has since been explored by us and others for constructing simple devices in the areas of lasers (11), fiber optics (12), inorganic microelectronics (13)(14)(15), microfluidic analytical chemistry (16), and biotechnology (17). We recently reported processing conditions that enable CP to be used for fabricating the source͞drain level in a variety of basic organic electronic devices (8,(18)(19)(20). Fig.…”

“…Removing the SAM exposes the bare gold and facilitates electrical contact with layers of organic semiconductors (8). In many cases, it is also possible to construct transistors by printing and etching gold films deposited on top of the semiconductor.…”

A microscopic model for the behavior of nanostructured organic photovoltaic devices

“…[3][4][5][6] They also offer the potential to reduce significantly the cost of photovoltaic energy [7][8][9] due to solution processing and continuous deposition techniques. However, despite improvements in materials 10 and device design, [11][12][13] power conversion efficiencies remain prohibitively low for commercial exploitation ͑1.7% in polymer blends 14 and 4.4% in polymer: fullerene systems 15 ͒.…”

Electric-field-controlled conductance of “metallic” polymers in a transistor structure

“…[1][2][3][4][5] Highly crystalline small molecule systems such as pentacene and ␣-sexithiophene structurally form parallel stacks of molecules with strong overlap of and * orbitals on adjacent molecules forming networks beneficial for charge transport. 6,7 Field effect mobilities ͑ FET ͒ as high as 1.5 cm 2 / ͑V s͒ have been reported for the organic semiconductor, pentacene.…”