Solution-Processed Thin Film Semiconductors for Photovoltaic and Photoelectrochemical Applications

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The reduction of greenhouse gas emissions to mitigate climate change while meeting the growing global energy demand is one of the greatest challenges of our time. Renewable energy technologies, such as photovoltaics (PV), have been identified by the Intergovernmental Panel on Climate Change (IPCC) to play a leading role in the necessary transition away from fossil-combustion-based energy sources. However, hurdles for widespread implementation such as cost competitiveness and the inherent energy intermittency of solar energy must be overcome. Ink-based deposition techniques have the potential to bring down costs and allow sustainable growth of renewable technologies due to their low capital expenditure, high material utilization, and high throughput, if high device efficiencies and benign reaction mechanisms can be obtained at the same time. Thin film solar cells based on chalcogenide and perovskite absorbers are particularly promising as they have achieved power conversion efficiencies of over 22%, representing the highest value among thin film solar cells exceeding the market-leading silicon technology and can be fabricated by liquid deposition methods and on a choice of rigid or flexible substrates. Moreover, both technologies exhibit a wide range of bandgap tunability, which allows for their integration in solution-processed tandem solar cells that can further boost device efficiencies by over 40% and potentially reduce solar electricity prices to approach those of coal or gas. High voltages from tandem devices further allow their use in catalysis reactions for solar fuels. The photoelectrochemical (PEC) reduction of CO2 has received growing attention as a potential solution to the intermittency of solar PV while reducing the amount of excess CO2 in the atmosphere. Solar energy harvested by PV is thereby used to convert CO2 into value-added hydrocarbon chemicals for storable fuels that may be used within the existing transportation infrastructure. Similar to solar PV, low-cost deposition methods and materials for catalysts and PEC devices are needed to guarantee the growth of the technology as well as cost-competitive solar fuels. The proposed research program to design, fabricate, and characterize solution-processed semiconductor layers and devices for PV and PEC applications is a highly interdisciplinary field that is expected to generate comprehensive qualifications for HQP in the area of semiconductor engineering, which is highly desired by both academia and industry. Further, this research has the potential to trigger a paradigm shift in semiconductor manufacturing and energy generation, challenging traditional conceptions of inferior material quality for solution-processed films and leverage Canada to gain IP and jobs in the ever-more-important renewable energy sector.