Novel nanoscale semiconductors for energy conversion and storage

Abstract

Demand for energy has skyrocketed across the world in the last several decades. The use of non-renewable energy sources like fossil fuels has impacted the global climate very negatively. Widespread implementation of renewable energy sources like solar energy and wind energy is necessary for maintaining sustainable economic growth around the globe. Access to safe drinking water is also severely limited across developing countries due to the lack of a cheap and ubiquitous form of energy for disinfection treatment of water. The work contained in this dissertation describes the development and analysis of three novel nanoscale semiconducting materials that cover different aspects of our urgent energy needs.

Finally, the material is tested in lithium-ion batteries to show that it enables high charge storage capacities (approximately seven times higher than that of the conventional material – graphite), high current densities, and long cycle life, which make it a strong candidate for high-performance lithium-ion batteries that could help in effective utilization of intermittent energy sources like the sun and wind.

Firstly, chalcogenide perovskite thin films of the material barium zirconium sulfide (BaZrS3) are presented as an alternative to environmentally unstable and toxic organic-inorganic halide perovskite materials for next-generation solar cells. A two-step process of synthesizing BaZrS3 thin films by chemical solution deposition and sulfurization is described. Detailed characterization of BaZrS3 is described to reveal the structural, morphological, and optical properties of the material. Environmental stability of BaZrS3 is also established with the help of temporal monitoring experiments. Environmentally stable photodetector devices of BaZrS3 are also exhibited to demonstrate the viability of the material for energy conversion in solar cells and other optoelectronic devices. Secondly, vertically oriented rhenium disulfide (ReS2) nanosheets grown by powder-based chemical vapor deposition are investigated as photocatalysts for solar-based disinfection of water. The substrate-independent vertical growth mechanism of ReS2 nanosheets is uncovered by using atomic-resolution electron microscopy. The material is then shown to be very effective at disinfecting water by killing water-borne bacteria upon exposure to visible white light by photogeneration of reactive oxygen species. Thirdly, red phosphorus nanoparticles are shown as a high-performance material for energy storage in lithium-ion battery anodes. Synthesis of red phosphorus nanoparticles anchored to a graphene nanosheet matrix by using electrospraying and subsequent far infrared reduction is described. The structural, morphological, chemical, and electrochemical characteristics of the phosphorus nanoparticle/reduced graphene oxide (P/rGO) composite are described.