Description
This thesis discusses the development of printed and flexible photovoltaic power systems, spanning both device-level and system-level design. Photovoltaic cells and multi-cell modules are designed and manufactured using solution-processed organic materials. The use of carbon nanotube films as a flexible, low-cost, solution-processed transparent electrode for photovoltaics is investigated. Then, photovoltaic modules are integrated with batteries into energy harvesting and storage systems with multiple power levels and form factors, optimized to deliver power to loads such as wearable medical sensors. The energy collecting potentials of these systems are evaluated under indoor and outdoor lighting conditions. Designing the solar module maximum power point to match the battery voltage, as well as optimizing load characteristics such as duty cycle, are shown to enable power systems with long-term wireless operation and high efficiency. Finally, screen-printed passive components are developed and demonstrated in a hybrid flexible voltage regulator circuit. In particular, high-quality printed spiral inductors satisfactory for power electronics applications are achieved through optimization of the geometry and fabrication. Overall, the high-performance devices and integrated system designs demonstrated here have the potential for significant impact in the areas of flexible, portable and large-area electronics.