Perovskite and Silicon Tandem Photovoltaic Cells for an Autonomous IoT Underwater Depth Meter

Water depth measurement is crucial for various sectors. In navigation, chart routes are drawn up starting from the knowledge of water depth. In flood management systems such data is exploited for mitigating flood risks. However, the bulk of the application scenarios in which such measurements are needed is usually remote and harsh, thus hindering human interventions (e.g., battery replacements). But, self-powered Internet of Things (IoT) sensor nodes are a valuable solution in such contexts, since they rely on energy harvesting systems. Moreover, if harvesters are integrated with sensing capabilities, then such nodes become inherently reliable, hence fostering their scalability for pervasive measurement systems. To this end, this paper presents a preliminary analysis of a self-powered IoT depth meter designed for underwater deployment. It exploits a tandem of solar cells, including a Perovskite Solar Cell (PSC) and a Silicon (Si) solar cell, that harvests energy from the light propagating underwater. Then, since light intensity is strictly related to water column height, the tandem can be effectively turned into an underwater depth meter. Preliminary results show the feasibility of such an idea, thus paving the way for further developments, since a 25 cm
²
tandem placed 1 m underwater is capable of harvesting up to 240 Wh on an annual basis.