PV-Tower solar cell for small footprint photovoltaic energy harvesting for the internet of things application

Abstract

Development of Internet-of-Things requires the deployment of self-powered wireless sensor nodes (WSN). Towards this end, photovoltaic cells are often used to harvest ambient light energy. On the other hand, it is desirable to reduce the size of the WSN circuits as much as possible. However, WSN miniaturization will lead to less area available for solar cells and consequently, insufficient energy harvested to power the WSN. In this work, we develop a PV-Tower solar cell concept that offers a large active surface area for light absorption, while occupying only a small footprint. We demonstrate silicon-based PV-Tower solar cells with footprint areas of 0.2 mm2, 0.4 mm2, and 0.6 mm2, which can generate ≈80 times more power than conventional solar cells over the same footprint. We have also fabricated a small footprint PV-Tower module prototype that comprises 10 PV-Tower solar cells connected in series, which exhibits an open circuit voltage of 5.1 V. At the maximum power point, the module can deliver a voltage of 3.6 V and a power of ≈66.7 mW, which translates to an output power per footprint of ≈78.5 mW cm−2. By optimizing the module design, we estimate that there is room to significantly reduce its footprint and increase the output power per footprint by ≈10 times to 785 mW cm−2. The results show that the PV-Tower solar cell can serve as a compact small footprint photovoltaic energy harvesting device that can address the physical size constraints posed by miniaturization of the WSN circuit.