Most previous attempts to create solar powered sensors have relied on small traditional silicon solar cells. While such cells can be efficient, long-lasting, and powerful under certain conditions, say the researchers, they are infeasible for ubiquitous IoT sensors.
For example, traditional solar cells are bulky and expensive to manufacture and at the same time are inflexible and unable to be made transparent - a useful feature for temperature-monitoring sensors placed on windows and car windshields. They're also really only designed to efficiently harvest energy from powerful sunlight, say the researchers, not low indoor light.
On the other hand, Perovskite cells offer the following advantages:
- They can be printed using easy roll-to-roll manufacturing techniques for a few cents each
- They can be made thin, flexible, and transparent
- They can be tuned to harvest energy from any kind of indoor and outdoor lighting.
The idea then, say the researchers, was combining a low-cost power source with low-cost RFID tags - battery-free stickers equipped with ultra-high-frequency antennas used to monitor billions of products worldwide. RFID tags rely on backscatter - a communication technique that transmits data by reflecting modulated wireless signals off the tag and back to a reader device. The reader pings the tag, which powers up and backscatters a unique signal containing information about the product it's attached to.