Printed organic semiconductors for ionizing radiation detection

In the last years, Organic Field-Effect Transistors (OFETs) have shown a great potential in the field of X-rays direct detection, thanks to the possibility of fabricating flexible devices with low toxicity and cost-effective deposition processes. In this thesis, the composition of the active layer of OFETs based on an organic small molecule (TMTES) blended with an insulating polymer (polystyrene) was studied as a function of the ratio between the two components, of the molecular weight of the polymer and considering the effects of the addition of a Parylene-C encapsulation layer. The study of the TMTES:PS ratio confirmed the results of previous works reported in literature for different materials that indicated a lower amount of polystyrene as preferable, while the analysis of the role of polystyrene molecular weight showed no significant impact caused by the variation of this parameter. On the other hand, the addition of an encapsulating layer was associated with a higher sensitivity (S=(13.7±0.9)·103 µC·Gy-1cm-2) and with a tendency to retain the electrical parameters after electrical and radiative stress. These results open new possibilities to tune the features of blended materials as active layers of OFETs for ionizing radiation detection and to better understand the role and potential of the use of encapsulation layers in this kind of devices.