Perovskite and Silicon Tandem Photovoltaic Cells as a Self-Powered Water Depth Measurement System

This article describes an underwater depth measurement system that combines sensing and energy harvesting using two solar cells in tandem configuration. The tandem is composed of a semitransparent perovskite solar cell (PSC) stacked on the top of a silicon (Si) cell. The structure implements a novel sensing technique for the measurement of water depth based on the differential reduction of the short-circuit current with the increase of the depth. The effectiveness of the proposed solution concerning the sensing task is demonstrated in the laboratory by means of a controlled experimental setup for depths up to 45 cm, both in fresh and salt waters. At the same time, the power generated by the two cells is measured demonstrating their usability as energy sources for integrated Internet of Underwater Things platforms. The results demonstrate that the depth can be measured with an accuracy in the order of a few centimeters, while the provided power is in the order of more than 100 mW. While these results have been achieved in controlled conditions, they can be seen as a promising starting point for their extension to higher depths and then to their test in a real environment.