Towards fully printed monolithic supercapacitor enabling the integration with carbon-based perovskite solar cells

In a world rapidly transitioning away from fossil fuels to reduce greenhouse gas emissions and climate change, the importance of green energy sources has become increasingly evident. Photovoltaics (PV) have emerged as an abundant and eco-friendly energy solution to meet the growing demand for power. Among its many applications, PV techonology could be used to power small electronic devices as an alternative to batteries that require periodic recharging or disposal. However, the intermittent nature of solar energy poses a challenge: a standalone photovoltaic module cannot replace electrochemical batteries, as its electrical output depends on atmospheric conditions, resulting in inconsistent power supply for electronic devices. Harvesting and Storage (H&S) systems offer a promising solution, being compact devices able to continuously self-charge by harvesting and storing energy from the environment. This master's thesis research focuses on the integration of a perovskite solar cell (PSC) with a supercapacitor (SC) to create an H&S device. Perovskite solar cells are an innovative technology known for their rapidly increasing efficiency and cost-effectiveness. Supercapacitors are attractive due to their extended life-cycle and adaptability, requiring no specific voltage or current for charging, allowing simple and direct integration with perovskite solar cells. This master thesis work aims to reduce the production cost of an H&S device by fabricating both the harvesting and the storage section monolithically, i.e. printing the required materials layers one on top of the other. This technique could allow to obtain a working device using cheap and safe materials and up-scalable techniques as screen-printing (SP), significantly lowering the production cost of these kind of devices and favouring the diffusion of this technology. In particular, monolithic perovskite solar cells with carbon-based hole extraction layer were fabricated and achieved a very high current density (approximately 25 mA/cm^2) and an acceptable efficiency (around 12%). They were paired with water processable supercapacitors based on organic and eco-friendly solvent which correctly stored and released the photogenerated charges. From the combination of these devices, a working H&S device was obtained, with a overall efficiency around 5%, which were used to power a small temperature sensor. This research demonstrates the potential of monolithic fabrication processes to create high-quality devices while simultaneously reducing production costs. A significant step in this direction was taken in this study by successfully developing a screen-printable capacitive slurry. This innovation can be applied to create a monolithic supercapacitor based on carbon materials.