Executive Summary : | OFET devices integrates the switch capability of a field effect transistor and the light emission capability of OLED into single planar device structure and have enormous potential to integrate into optoelectronic devices, particularly appealing for display technology. The proposal focusses on the development of light emitting field effect transistors (OLET) with defect free, highly ordered, densely packed organic conjugated semiconductor materials as active medium for high current densities, brightness, control over emission zone, high aperture ratio and low operational voltages. The major difficulty of employing the organic semiconductors as active medium is the low charge carrier mobilities and the necessity of high luminescence efficiencies. Single crystals and crystalline thin films due to dense molecular packing and defect free long-range order are ideal active materials for planar single layer OLET devices. Implementation of single crystals, doped crystal and crystalline thin films with high luminescence and charge transport properties lies in the heart of the project. The low luminescence efficiencies of the planar π-conjugated chromophores in condensed phase will be circumvent by employing AIEE moities in conjunction with the planar π-conjugated core. The initial results from a luminescence point of view are promising. Ambipolar charge transport in the OFET devices will be explored for low operational voltage and control over emission zone. Asymmetric source-drain electrodes as well as the emissive CT crystals will be employed for ambipolar OLET. Dielectric materials with covalent functionalization to the active materials will be explored to overcome trap sites and interfacial homogeneity. As an initial step, emissive Aza[7]helicene chromophores functionalized with trimethoxysillane as anchoring group to form self-assemble monolayer on SiO2 gate dielectric. The molecular design allows us to incorporate alkylthiols functionalized planar π-conjugated chromophores with AIEE moieties to attach to the gold electrode to reduce Shockley barrier for Ohmic contact. Split gate device geometry will be employed to attain independent control over the charge carriers and attaining high brightness. The OLET devices also opens up the possibility of investigating charge injection, carrier mobilities, influence of the work function of electrodes on ambipolar transport, dielectric materials on field induced transport, charge recombination, exciton-polaron quenching and exciton decay leading to luminescence in a single device from a fundamental science view point. The success of high performance OLET device subsists in two worlds, materials with high charge transport, luminescence and innovative device design to incorporate/tackle the fundamental limitations of the materials. The project put forward strategies to overcome the limitations and the successful implementation of the project help us to attain a world leading position. |