The researchers created the sensors by mounting thin-film perovskite solar cells — known for their potential low cost, flexibility, and relative ease of fabrication — as energy-harvesters on inexpensive radio-frequency identification (RFID) tags. In addition to working under various lighting conditions, say the researchers, the solar-powered sensors were capable of greater data-transmission distances and multiple sensors could be integrated onto a single radio-frequency ID (RFID) tag.
"In the future, there could be billions of sensors all around us," says Sai Nithin Kantareddy, a PhD student in the MIT Auto-ID Laboratory. "With that scale, you'll need a lot of batteries that you'll have to recharge constantly. But what if you could self-power them using the ambient light? You could deploy them and forget them for months or years at a time. This work is basically building enhanced RFID tags using energy harvesters for a range of applications."
When testing the sensors by using them to continuously monitor indoor and outdoor temperatures over several days, the researchers found that the sensors transmitted data continuously at distances five times greater than traditional RFID tags. The longer data-transmission ranges mean, among other things, say the researchers, that one reader can be used to collect data from multiple sensors simultaneously.
The sensors could potentially be left inside or outside for months or even years at a time - depending on environmental conditions such as heat and moisture - before they degrade enough to require replacement. This would be ideal for any application requiring long-term sensing, indoors and outdoors, including tracking cargo in supply chains, monitoring soil, and monitoring the energy used by equipment in buildings and homes.