Surface Morphology and Mechanical Characterization of MoO3/PEDOT:PSS Blend Thin Films For Organic Solar Cells and Light Emitting Diode Applications

Kum, Tatchen Buh (2022-09-07)

Main Thesis


Access to cheap and reliable electricity is a requirement for improved quality of life and industrialization. Solar energy harvesting for electricity generation has been a promising area where solar cells are combined into modules and then panels are used to harvest solar energy for electricity. However, the initial acquisition cost of active solar is still a major barrier. There is therefore a dire need for efficient and affordable solar technologies to help mitigate the current global energy crisis. Organic and perovskite photovoltaics pose superior properties and cheaper costs. Degradation, stability, and durability are the current issues faced with organic and perovskite solar cells stopping them from being commercialized or used in a large scale. It is important to carefully study the different thin films layers making up these devices to investigate these issues of stability, degradation and durability. Over the years, both experimental and computational techniques have been used to study these issues. The mechanical properties of these thin film devices are very crucial for the development and implementation of mechanical durable devices.In this work, nanoindentation is mainly employed to investigate the effects of annealing temperatures and MoO3 blended ratios on the surface morphology, sheet resistance, mechanical properties as well as microstructure of PEDOT:PSS/MoO3 thin film blends as hole transport materials (HTM) for photovoltaics and OLED applications. Results from this study suggest that, the introduction of different percentages of the transition metal oxide (MoO3 ) into PEDOT:PSS significantly modifies the surface morphology, microstructure and mechanical properties in the different temperature regimes. (60 0C, 80 0C, 100 0C, 120 0C). Furthermore, PEDOT:PSS/MoO3thin film blends with small blended ratios of MoO3 (1:0.1 and 1:0.3) generally exhibit low sheet resistances, better surface morphologies and a good balance in mechanical properties (elastic vi modulus and hardness). A balance of properties as in hybrid thin films with low blended ratios is required to develop efficient and mechanical durable electronic devices. Finally, it was also found that, high blended ratios of MoO3 leads to high surface roughness and high sheet resistance which are unfavorable for device performance.