The properties of the dielectric strongly influence the performance of organic thin-film transistors. In this letter, we show experimental results that quantify the influence of the roughness of the dielectric on the mobility of pentacene transistors and discuss the cause of it. We consider the movement of charge carriers out of the "roughness valleys" or across those valleys at the dielectricsemiconductor interface as the limiting step for the roughness-dependent mobility in the transistor channel.

A main focus of research on organic semiconductors is their potential application in passive organic radio-frequency identification (RF-ID) tags. First prototypes working at 125 kHz have been shown by industrial research groups. However, to be commercially viable, the organic RF-ID tag would need to be compatible with the base-carrier frequency of 13.56 MHz (ref. 2). High-frequency operation has been out of reach for devices based on organic semiconducting material, because of the intrinsically low mobility of those materials. Here, we report on a rectifier based on a pentacene diode that can rectify an incoming a.c. signal at 50 MHz. At 14 MHz, a rectified voltage of 11 V for an a.c. voltage with a peak-to-peak amplitude of 36 V has been achieved. On the basis of those results, we estimate the frequency limits of an organic diode showing that even the ultra-high-frequency band at around 800 MHz is within reach.

The concept of noise margin is crucial in the design and operation of digital logic circuits. Analytical expressions for the transfer curves of an inverter based on two depletion-mode p-type organic thin-film transistors (OTFTs) were calculated. Based on these expressions, the values for the noise margin of organic-based inverters were calculated. In this paper, the influence of the OTFT parameters on the noise margin is presented. Knowing that statistical variations of the transistor parameters are inherent to OTFT technology, these statistical variations are also taken into account. Finally, a circuit yield analysis is presented.