Fundamentals of Organic Colloidal Composite Nanoparticles Applicable in Optoelectronics: Study of Morphology Formation, Surface Treatment and Charge Carrier Transport

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The use of aqueous / alcohol-based nanoparticulate dispersions in printable optoelectronics offers a promising approach to control the donor: acceptor morphology on the nanoscale with the benefit of environmentally-friendly, solution-based fabrication. Appropriate nanoscale morphology of the donor: acceptor composite nanoparticles (NPs), such as Janus structure, is the prerequisite for a well-suited mesoscale morphology formation to ensure an efficient charge transport. The final nanostructure of a composite NP is determined by the competition between thermodynamics (e.g. solubility, stabilizer, etc.) and kinetics (e.g. solvent evaporation, polymer ordering, etc.) during the particle formation. However, fine tuning and control of these variables require prior observations and in-situ measurements. In this proposal, we will focus on the fundamentals investigation of colloidal organic composite NPs in terms of NPs morphology formation, NPs surface treatment, mesoscale microstructure of NP-incorporated films, and transport dynamics for application in organic electronic devices with an emphasis on making comparisons between donor: fullerene and donor: non-fullerene composite NPs. In this regard, the project will be divided to following four work packages (WPs):WP-1: A new portable synthesis setup based on stopped-flow apparatus equipped with UV-Vis absorbance spectroscopy, fluorescence spectroscopy and light scattering techniques will be established for the in-situ analysis of the size growth and morphology evolution of organic colloidal NPs. The setup will enable a rather easy integration with a number of various beamlines for performing advanced X-ray diffraction and infrared spectroscopy.WP-2: Real time multi-parameter measurements will be carried out using our developed setup to gain in-depth fundamental knowledge on the processes and mechanisms controlling the size and nanoscale morphology of nominated polymer: fullerene and polymer: non-fullerene composite nanoparticles as a function of a series of factors such as the physicochemical properties of the organic components and preparation process (surfactant, solvent, temperature, mixing rate, etc.).WP-3: The mesoscale morphology of the NP-incorporated thin films will be investigated by a combination of ex-situ and in-situ optoelectrical as well as structural characterization techniques in terms of impact of the essential parameters such as thermal and solvent annealing post-treatments and NP-surface treatments on the particles assembly in solid films and microstructure formation. WP-4: The success of controllable nano- and meso-scale morphology formation of organic colloidal composite NPs will be demonstrated in high performance optoelectronic devices such as photovoltaics.The outcome of the research described above will shine light on the potential and limitations of organic NPs for the next generation of various organic optoelectronic devices.