Aging control of organic thin film transistors via ion-implantation

One of the open issues in organic electronics is the long-term stability of devices based on organic materials, as oxidation is believed to be a major reason for early device failure. The focus of our research is to investigate the effects of low energy ion implantation (N and Ne) in the reduction and control of the degradation of pentacene organic thin film transistors (OTFTs) due to the exposure to atmosphere (i.e. oxygen and water). Despite the strong molecular structure modifications induced by ion implantation, we have observed that a controlled damage depth distribution preserves the functionality of the device. The electrical properties of the pentacene layer and of the OTFT have been investigated by means of current-voltage and photocurrent spectroscopy analyses. We have characterized the structural modification induced by ion implantation and we have monitored the effectiveness of this process in stabilizing the device carrier mobility and threshold voltage over a long time (over 2000 h). In particular, we have assessed by depth resolved X-ray photoemission spectroscopy analyses that, by selectively implanting with ions that can react with the hydrocarbon matrix (e.g. N+), it is possible to locally modify the charge distribution within the organic layer.