Molecular Design and Modification of Organic Materials for Opto-electronic and Tribo-electric Devices

Abstract

Over the past two decades, energy harvesting using wasting is critical issue. Energy harvesting is essential, as it is abundant in our life environment. Among harvesters, organic photovoltaics (OPVs) using cunjugated polymers or smallmolecules, organic field-effect transistors (OFETs), and triboelectric nanogenerators (TENGs) are representative harvesters and exhibit good performance. Among a large number of materials reported in the related literature such as benzodithiophene (BDT), diketopyrrolopyrrole (DPP), isoindigo (IIG), TPTI is a promising material for optoelectronic device application (polymer solar cells and organic field-effect transistors). In accordance with this, in chapter 1, I performed in-depth study about the relationship between random terpolymer and polymer solar cell performance based on TPTI as the donor and PCBM as the acceptor. Incorporating random terpolymerization strategy unlike alternating donor-acceptor copolymer, TPTI-based random terpolymers with thiophene and bithiophene moieties (PTPTI-Tx) were investigated for polymer solar cells (PSCs). Particularly, correlation between crystalline allignment from surface to the whole film depth in the TPTI-Tx:PCBM blend films and the PSCs performance was investigated deeply. In chapter 2, with TPTI-Tx random terpolymers which described in chapter 1, a fused-aromatic-ring-based acceptor (m-ITIC) was introduced as non-fullerene acceptor. I explored TPTI-Tx:m-ITIC blends characters including optical, electrical energy, morphology, crystalline packing in the non-fullerene polymer solar cells. Also, in chapter 3, I simultaneously tuning the molecular weight and alkyl substituents based on thienoisoindigo-naphthalene copolymer (PTIIG-Np) for organic field-effect transistors (OFETs). Through stoichiometry imbalance of monomers, I systematically synthesized low and high molecular weight PTIIG-Np polymers with three different alkyl substituents. In chapter 4, I deeply studied about modulating of PVDF dielectric material via Atom Transfer Radical Polymerization (ATRP) to enhance triboelectric nanogenerator performance. By controlling the reaction time with the fixed catalyst system and monomer conditions, PVDF-graft tert-butyl acrylate copolymers (PVDF-Gn) have been synthesized and characterized. Inducing improved dielectric constant, Difference of TENG performance depending on the graft extend and degree of dielectric constant has been demonstrated relating to the structure of PVDF-Gn. Also, we intertwined the morphology and crystalline structure of PVDF graft copolymers with the TENGs performance.