At present, flexible displays are an important focus of research. Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel. One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate. Here, we demonstrate flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-microm-thick polyimide substrates. The displays can be bent to a radius of 1 cm without significant loss in performance. Using the same process flow we prepared row shift registers. With 1,888 transistors, these are the largest organic integrated circuits reported to date. More importantly, the operating frequency of 5 kHz is sufficiently high to allow integration with the display operating at video speed. This work therefore represents a major step towards 'system-on-plastic'.

We demonstrate a rewritable, non-volatile memory device with fl exible plastic active layers deposited from solution. The memory device is a ferroelectric fi eld-effect transistor (FeFET) made with a ferroelectric fl uoropolymer and a bisalkoxy-substituted poly(p-phenylene vinylene) semiconductor material. The on-and off-state drain currents differ by several orders of magnitude, and have a long retention time, a high programming cycle endurance and short programming time. The remanent semiconductor surface charge density in the on-state has a high value of 18 mC m -2 , which explains the large on/off ratio. Application of a moderate gate fi eld raises the surface charge to 26 mC m -2 , which is of a magnitude that is very diffi cult to obtain with conventional FETs because they are limited by dielectric breakdown of the gate insulator. In this way, the present ferroelectricsemiconductor interface extends the attainable fi eldeffect band bending in organic semiconductors.A memory element based on the ferroelectric fi eld-effect transistor (FeFET) is attractive because of its non-volatile data retention, small size, rewritability, non-destructive read-out, low-voltage operation and short programming time 1 . Its functionality arises from the attenuation of the charge carrier concentration in the semiconductor by the ferroelectric polarization of the gate insulator. Even though inorganic FeFETs have been studied for decades, a memory performance of any practical value has been achieved only in recent years [2][3][4][5][6][7][8] . The main problems that have arisen are charge trapping at the ferroelectric-semiconductor interface and the lack of thermal stability of the interface. This has prompted the use of insulating buffer layers between the semiconductor and ferroelectric to prevent charge injection and protect the semiconductor from the high-temperature annealing procedure that is required for inorganic ferroelectrics. Crucial device parameters for all memory devices are the on/ off ratio, data retention time, programming cycle endurance and programming time. Current state-of-the-art inorganic FeFETs have on/off ratios up to 10 9 , a retention time of 16 days and a programming time of 10 -8 s (refs 5,8). This is promising, although the high production cost of this non-CMOS (complementary metal-oxide-semiconductor) technology may hinder widespread application.Organic fi eld-effect transistors are ideally suited for low-cost, low-performance logic circuit applications on fl exible substrates 9 .

Organic thin-film transistors (OTFTs) offer unprecedented opportunities for implementation in a broad range of technological applications spanning from large-volume microelectronics and optical displays to chemical and biological sensors. In this Progress Report, we review the application of organic transistors in the fields of flexible optical displays and microelectronics. The advantages associated with the use of OTFT technology are discussed with primary emphasis on the latest developments in the area of active-matrix electrophoretic and organic light-emitting diode displays based on OTFT backplanes and on the application of organic transistors in microelectronics including digital and analog circuits.