Executive Summary : | The use of organic field-effect transistors (OFETs) in stretchable and wearable electronic devices has increased drastically in many aspects of our daily life. We are switching to wireless smart technology including wireless payment, wireless keys, wireless fitness detection, wireless sensors for health and wellness applications, to name a few. The use of smartwatches is also increasing day by day and incorporating more smart features into the existing technology is a topic of interest. Therefore, considering the current scenario, smart wireless technology is in high demand and research to enhance the performance of OFETs to be used in those devices is highly desirable. The use of ambipolar material in such a device with balanced electron/hole mobilities can overcome several compatibility issues of two different p-type and n-type materials. Here, we propose naphthalenediimide (NDI) based donor-acceptor copolymers to be used in ambipolar OFET. NDI building-block shows excellent n-type conductivity and there is a scope of improving the p-type conductivity by structurally modifying the thiophene-based donor units in order to have balanced hole/electron conductivities. The device performance is highly dependent on the charge carrier mobility which further depends on the charge carrier distribution within the polymer chains and interchain distributions. Conductivity can be tuned in one way by modifying the π-conjugated building blocks which can be better understood from the electronic structures. In this regard, the present work proposes the incorporation of fused π-conjugated thiophene moieties to improve hole mobility which will be studied using density functional theory (DFT). Another way to enhance device performance is controlling the film morphology i.e., controlling the ordering of the polymer chains and the crystallinity of the film. For instance, π-π stacking among the polymer chains and percolative network of it is necessary for the charge transport in the active layer as π-orbitals overlap determines the interchain hopping of the charge carrier. Morphology insights will be elucidated through computational microscopy using molecular dynamics (MD) simulations. The arrangement of the polymer chains further depends on the substrate. Substrate plays the role in the different arrangements of the polymer chain, e.g., face-on, edge-on, end-on. Moreover, a large part of OFET devices is occupied by the substrate. Concerning the e-waste produced from the electronic devices, a biodegradable cellulose-based substrate with low environmental footprint will be used. Finally, mechanical properties of the film, percolation study of the π-π stacks in the film and mobility calculation of the free charge carriers will be carried out using MD and kinetic Monte Carlo simulations. |