Development of light-sensing organic transistors for optoelectronic and image sensor array applications

Traditionally, organic field-effect transistors (OFETs) have been explored as electronic switches in organic integrated circuits and active-matrix flexible displays. Recently, however, OFETs with additional functionalities, i.e. bi-functional OFETs, have also made their debut with most notable examples the light-emitting (LE-OFETs) and light-sensing (LS-OFETs) transistors. It is the aim of this project to design, develop and study bifunctional OFETs for use in various optoelectronic applications. In particular, we aim to demonstrate LS-OFETs with high photoresponsivity and fast switching characteristics for use, primarily, in integrated photodetectors, electro-optical circuits and full-colour/monochromatic image sensor arrays. Our approach is based on the use of suitable ambipolar OFETs and the measurable photoinduced current present upon illumination of the device with light. The significant concentration of free carriers, generated upon photoexcitation, can modulate the current flow across the channel and hence transform the transistor to an electro-optical switch. Use of ambipolar LS-OFETs has the potential to maximise the photoresponse of the devices while incorporation of appropriate semiconductor systems is expected to lead to demonstration of LS-OFETs with a wavelength selective characteristics. Such devices could one day be exploited in low-cost, large-area and flexible image sensor array applications. Furthermore, demonstration of high-performance LS-OFETs will also pave the way towards electro-optical circuits, in which signal processing involves the use of both optical and electrical signals. To date these ideas have not been given any significant consideration and are therefore waiting to be exploited. If succeed the proposed work has the potential to reshape the landscape of traditional organic electronics.