In traditional electronics, inorganic materials such as silicon and germanium are used as semiconductors due to their outstanding semiconducting properties. Unfortunately, inorganic materials are rigid due to their high crystalline nature, and processing these materials is complex and expensive. Furthermore, traditional semiconducting materials do not have favorable mechanical properties in applications such as wearable devices and large-area applications with complicated shapes. Conjugated conducting polymers (CCPs) are being explored as alternative materials to conventional semiconductors due to their mechanical properties and high conductivity. CCPs offer properties such as solution and low-temperature processability, flexibility, thermal and optical properties that traditional semiconductors could not provide. These characteristics are essential in Organic Light-Emitting Diodes (OLEDs), Organic Field-Effect Transistors (OFETs), and Photovoltaic (PVs) devices. This dissertation focuses on synthesizing rhodamine- and diketopyrrolopyrrole- containing CCPs. Chapter I focuses on the synthesis, and characterization of polyrhodamine (PRho), a semiconducting conjugated polymer containing the rhodamine core in the polymer’s backbone. PRho was synthesized by the Buchwald-Hartwig polycondensation and characterized for its optical and electrochemical properties. We have discovered that the polymer is electrochemically reversible and stable up to 1000 cycles as recorded by cyclic voltammetry between -0.4 and 1.0 V vs. Ag/AgCl and stable to extreme acidic and basic conditions without noticeable degradation. Remarkably, the polymer has a conductivity in the semiconductor range of 8.38 x 10-2 S cm–1 when treated with 20% HCl. Chapter II focuses on the synthesis and characterization of four different alkenyl flanked diketopyrrolopyrrole (DPP) polymers ( PDPPVTV, PDPPVTT, PDPPV3T, and PDPPV4T) synthesized via Stille polycondensation. Different pi-conjugated segments (alkenyl/ PDPPVTV, thiophene/ PDPPVTT, thienothiophene/ PDPPV3T, and dithienothiophene/ PDPPV4T) were used to tune the optoelectrical properties of the polymers. The effect of the alkenyl groups and different pi-conjugated segments on the optoelectrical and charge mobility properties were determined by UV/visible spectroscopy, cyclic voltammetry, and FET characteristics. Three of the four polymers, except PPP4T, showed good solubility in chloroform. All the polymers showed high thermal stabilities in TGA and semi-crystalline nature in X-Ray diffraction patterns. PDPPVTV and PDPPVTT exhibited hole mobilities of 1.8 x 10-3 cm2 V-1 s-1 and 0.25 cm2 V-1 s-1, respectively. .
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-6525 |
| Date | 13 May 2022 |
| Creators | Wahalathantrige Don, Ranganath Wijesinghe |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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