Photovoltaic-Powered Sensors for the “Internet of Things”

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The key innovations are in the customized cells. They’re fabricated in layers, with perovskite material sandwiched between an electrode, cathode, and special electron-transport layer materials. This achieved about 10 percent efficiency, which is fairly high for still-experimental perovskite cells. This layering structure also enabled the researchers to tune each cell for its optimal “bandgap,” which is an electron-moving property that dictates a cell’s performance in different lighting conditions. They then combined the cells into modules of four cells.

In the Advanced Functional Materials paper, the modules generated 4.3 volts of electricity under one sun illumination, which is a standard measurement for how much voltage solar cells produce under sunlight. That’s enough to power up a circuit — about 1.5 volts — and send data around 5 meters every few seconds. The modules had similar performances in indoor lighting. The IEEE Sensors paper primarily demonstrated wide‐bandgap perovskite cells for indoor applications that achieved between 18.5 percent and 21. 4 percent efficiencies under indoor fluorescent lighting, depending on how much voltage they generate. Essentially, about 45 minutes of any light source will power the sensors indoors and outdoors for about three hours. 

The RFID circuit was prototyped to only monitor temperature. Next, the researchers aim to scale up and add more environmental-monitoring sensors to the mix, such as humidity, pressure, vibration, and pollution. Deployed at scale, the sensors could especially aid in long-term data-collection indoors to help build, say, algorithms that help make smart buildings more energy efficient.

“The perovskite materials we use have incredible potential as effective indoor-light harvesters. Our next step is to integrate these same technologies using printed electronics methods, potentially enabling extremely low-cost manufacturing of wireless sensors," Mathews says.

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