Chung-Chen Kuo

Analog and digital circuits using organic thin-film transistors on polyester substrates

We have fabricated and characterized analog and digital circuits using organic thin-film transistors on polyester film substrates. These are the first reported dynamic results for organic circuits fabricated on polyester substrates. The high-performance pentacene transistors yield circuits with the highest reported clock frequencies for organic circuits.

A reduced complexity process for organic thin film transistors

A simplified device structure for depletion-mode organic thin film transistors is described in which the gate electrode and the source/drain contacts are prepared in the same process step, thus reducing the number of material depositions and photolithography steps. Based on the simplified device structure and using the small-molecule aromatic hydrocarbon pentacene as the active material, organic thin film transistors were fabricated on glass substrates with carrier mobility of 0.6 cm2/V s, on/off current ratio of 105, and subthreshold slope of 0.5 V/decade.

High-mobility, low voltage organic thin film transistors

We have fabricated photolithographically defined organic thin film transistors (TFTs) on glass or plastic substrates with carrier field-effect mobility larger than 1 cm/sup 2//V-s, using the organic semiconductor pentacene as the active layer. In addition to high carrier mobility, devices on glass substrates have subthreshold slope as low as 0.4V/decade. TFT performance for devices on both substrate types was extracted at low bias (less than -30 V). These results are the best reported to date for organic TFTs on polymeric and glass substrates.

High mobility solution-processed OTFTs

Using bis(triisopropylsilylethynyl)pentacene (TIPS -pentacene), we have fabricated solution-processed OTFTs with mobility near 1.5 cm2 /Vmiddots. This is the highest mobility reported to date for solution-processed OTFTs. The organic semiconductor thin films used in these devices require no high temperature processing and also show remarkable molecular ordering, possibly related to the observed high mobility. This work demonstrates that solution processed OTFTs with characteristics similar to vacuum deposited devices are possible and provides a possible path to low-cost organic electronics processing

Fast organic circuits on flexible polymeric substrates

We have fabricated the fastest organic circuits on flexible substrates yet reported. These circuits use the small-molecule hydrocarbon pentacene as the active semiconductor material and 75 /spl mu/m thick flexible, transparent, colorless, polyethylene naphthalate (PEN) film as the substrate. Transistor arrays, inverters, ring oscillators, and other circuits with good electrical performance, yield, and uniformity were obtained. A field-effect mobility of 1 cm/sup 2// V-s was extracted from OTFT saturation characteristics, and ring oscillators had minimum propagation delay <40 /spl mu/sec per stage and <50 /spl mu/sec per stage at bias levels below 8 V.

Organic thin film transistors with field effect mobility >2 cm/sup 2//V-s

We report pentacene-based organic thin film transistors (OTFTs) with field effect mobility as large as 2.1 cm/sup 2//V-s. To our best knowledge this is the highest field-effect mobility reported for an OTFT.

TES anthradithiophene solution-processed OTFTs with 1 cm/sup 2//V-s mobility

We have fabricated solution processed organic thin film transistors (OTFTs) based on triethylsilylethynyl anthradithiophene (TES anthradithiophene) with 1 cm/sup 2//V-s mobility. The devices also have current on/off ratio > 107 and subthreshold slope near 1 V/decade. To our knowledge, these are the highest mobility solution-processed OTFTs reported to date and the first with performance comparable to thermally evaporated pentacene devices.

An organic thin film transistor backplane for flexible liquid crystal displays

Organic thin film transistors (OTFTs) have made impressive progress over the past decade, and it appears increasingly likely that OTFTs will find use in a number of low-cost, large-area electronic applications, such as active-matrix displays, smart cards, price and inventory tags, and large-area sensor arrays. OTFTs provide two principal advantages over TFTs based on inorganic semiconductors: they can be fabricated at lower temperature and, potentially, at significantly lower cost. Low processing temperatures allow OTFT device and circuit fabrication on polymeric or other inexpensive substrates, rather than glass. The prospect of a flexible, rugged, lightweight active-matrix display at relatively low cost has spurred a number of manufacturers and government agencies to consider plastic displays for a variety of military, medical, industrial, and consumer applications. We report here on the design and fabrication of a flexible active-matrix OTFT backplane suitable for use in flexible polymer-dispersed liquid crystal displays. 75 /spl mu/m thick flexible polyethylene naphthalate (PEN) film was used as the substrate, and OTFT and pixel arrays with good electrical performance, yield, and uniformity were obtained.

Solution processed OTFTs with 1 cm/sup 2//V-s mobility

This work presents fabricated solution processed organic thin film transistors (OTFTs) based on triethylsilylethynyl thienyl pentacene (TES thienyl pentacene) with 1 cm/sup 2//V-s field-effect mobility. The devices also have an on/off current ratio >10/sup 7/ and subthreshold slope near 1 V/decade. To our knowledge, these are the highest mobility solution processed OTFTs demonstrated to date and the first with performance comparable to thermally evaporated pentacene devices.

Directly lithographic top contacts for pentacene organic thin-film transistors

Recent organic thin-film transistor (OTFT) research has focused on real applications for flat panel displays, smart cards, and smart inventory tags, often based on small molecule organic semiconductors such as pentacene. A resolution of 1 /spl mu/m in the fabrication of OTFTs is required for these purposes. It has been a major challenge to fabricate top contacts on the organic semiconductors, based on the fact that devices usually have a lower contact resistance than that of organic devices with bottom contacts. In this paper, we report the fabrication process of lithographic source/drain top contacts of pentacene OTFTs with mobility greater than 0.3 CM/sup 2//V-s. To our best knowledge this is the first work of directly patterning top contacts on OTFTs and demonstrating the desired performance for applications.