The project takes on the challenge of mastering the physics, chemistry and technology of Organic Semiconductors to combine a transistor and a photodetector in a single integrated active pixel that, when organized in a two dimensional array, may lead to an “organic imager”. The perspective application will be the digital X-ray image sensor array, in which the matrix of pixels is coupled to a scintillator for the conversion of X-ray radiation into visible photons, with the aim of replacing the slow, conventional film-based X-ray process with an instantly digitized X-ray image.
The project aims to the realize multiple, interconnected, interoperating organic devices developed on the same substrate and integrating the different functionalities (such as sensing, amplifying, and addressing) required by even the simplest optoelectronic system.
The complexity of this research lies on two facts:

1. different functions, generally speaking, neeb different materials to be deposited on the same substrate;
2. unlike the inorganic counterpart, subtractive lithographic patterning can hardly be applied due to the sensitivity of organic materials to processing conditions.

In order to address these issues, we take advantage of state-of-the-art drop-on-demand inkjet printing. This technique has the unique ability to deliver small and controlled quantities (picoliters to nanoliters) of functional inks only over the area where it is actually needed and on an arbitrary substrate, enabling fully bottom-up processes.
The task of inkjet printing an imager places this project at the forefront of printed electronics research, with issues in ink formulation, device integration, process engineering and uniformity over large areas. To master the building blocks of the imager pixel (photodetector and oFET), the project will address fundamental issues in the field of light-matter interaction and charge carrier transport, respectively. The development of ink-jet technology for the deposition of “electronic” functional materials requires the consolidation of a number of cross-disciplinary competences and of a considerable know-how in the field of functional materials that must be formulated into inks, whose physical properties (viscosity, surface tension, etc.) must be made compliant with the printing process. The project is also relevant in terms of the specifically targeted application. In fact, the major constraint in X-ray imaging is the lack of convenient means for focusing x-ray radiation, which implies that the digital panels must necessarily be as large as the objects they are designed to image: in the case of mammography and chest radiography, for instance, areas larger than 10x10cm² are required. To develop an electronic system, converting photons into electrons, large area constraints rule out the use of crystalline silicon because costs would be unaffordable. Moreover, with amorphous silicon, which can provide large area coverage, the cost is such that digital radiography uptake has been considerably slowed. The organic X-ray imager will address these issues, since organic electronics holds the potential for combining the low cost of fabrication together with large-area compatibility.