Date: Thursday, April 11th, 2019
Time: 12:00 p.m.
Title: Development of Molybdenum-Nitride-Graphite Supercapacitor Electrodes Produced from Solution Precursor Plasma Spray
Presenter: Hugo Caouette-Fritsch (MASc Candidate)
Supervisor: Professor T.W. Coyle
Energy storage devices capture energy and store it for a later use in time. They encompass a wide range of technologies such as flywheels, batteries, capacitors, and fuel cells. These inventions provide the energy we consume while we are not directly connected to the electrical grid. They are ubiquitous in our everyday lives, yet simultaneously inconspicuous. In this seminar, I will discuss the fabrication, the characterization and the electrochemical testing of molybdenum-nitride-graphite supercapacitor electrodes. Molybdenum was chosen as the material of study because of its numerous oxidation states, which typically translate well to an increased electrochemical charge storage. Moreover, molybdenum is a relatively low-cost option in comparison to ruthenium oxide – the gold standard for metal-based supercapacitor electrodes. The primary objective of this research is to investigate the effects of the operating parameters of plasma spray vis-à-vis the electrode’s microstructure and electrochemical properties. The electrodes were characterized using a scanning electron microscope (SEM), an x-ray diffractometer (XRD), a photoelectron spectrometer (XPS), and a potentiostat.
Title: Energy disorder and energy level alignment in doped organic semiconductors.
Presenter: Peicheng Li (PhD Candidate)
Supervisor: Professor Z.H. Lu
Energy level alignment between host and dopant molecules plays a critical role in exciton formation and harvesting in light emission zone of organic light-emitting diodes. Understanding the mechanism for predicting energy level alignment is thus important in materials selection for fabricating high-performance organic light-emitting devices. Here we show that host-dopant energy level alignment strongly depends on film thickness and substrate work function by using X-ray and ultraviolet photoemission spectroscopy. Invariant Gaussian density of states fails to explain the experimental data. We speculate that energy disorder in molecules next to the surface dictates the alignment. Ultraviolet photoemission spectroscopy measurements of several archetypical organic semiconductors confirm our speculation. An empirical interface disorder function is derived and used to construct a functional Gaussian density of states to compute host energy levels. Host-dopant energy level alignment is then computed by applying the universal energy alignment rule and is found in excellent agreement with the experimental data.