Materials Science and Engineering Ph.D. Dissertation

 

Abstract

The 20th century witnessed a profound transformation in human existence, with the advent of electronics propelling societies from the industrial era into the information age. As we entered the 21st century, organic electronics emerged as a contemporary frontier, harnessing carbon-based molecules and polymers to create novel devices like organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). However, while organic materials offer benefits such as flexibility and cost-efficiency, they face challenges like limited charge mobility and environmental sensitivity. This work represents a significant shift towards eco-friendly material synthesis and innovative performance enhancement, providing a glimpse into the future of organic electronics.

This study showcases a shift toward eco-friendly material synthesis, exemplified by liquid-phase exfoliation of MoS₂ and WS₂ using NH₃(aq). This process yields high-quality 2D materials with exceptional potential as hole transport layers (HTLs) in organic solar cells (OSCs), achieving power conversion efficiencies (PCE) up to 15.6%. This research underscores the promise of NH₃(aq)-based exfoliation for 2D materials and their application in high-performance OSCs.

Next, efforts to enhance the thermoelectric properties of PEDOT: PSS films are explored, emphasizing the integration of 2D materials and doping methods to improve electrical conductivity, Seebeck coefficient, and thermoelectric efficiency.

This work also introduces a novel approach to enhance PEDOT: PSS film conductivity. A sequential treatment involving HNO₃ and CsCl significantly increased conductivity from ≈1 S cm^-1 to >5500 S cm^–1. Even after 270 days in ambient conditions, treated films retained over 85% of their initial conductivity, making them valuable transparent electrodes in organic electronics.

Last, the study highlights the thermoelectric potential of PEDOT: PSS, focusing on controlled reduction processes and high-dielectric-constant solvents. Various Cs derivatives in different solvents show promise in enhancing the Seebeck coefficient and power factor (PF), especially Cs₂C₂O₄. Combined with CsCl-treated PEDOT: PSS films, these treatments offer the potential for efficient energy conversion in organic thermoelectric generators (OTEG).

Incorporating inorganic materials into organic electronics offers a pathway to overcoming the limitations of pure organic systems. This integration holds the key to unlocking the full potential of organic electronics, driving advancements in flexible displays, energy generation, and wearable electronics.