RFID (Radio-Frequency Identification) is a popular technology because it doesn’t require a conventional power source. Your office keycard, for example, doesn’t need an integrated battery, which gives it a limitless lifespan. That’s possible because the radio waves being emitted by the RFID reader carry enough power to energize the RFID chip and allow it to transmit a small amount of data back to the reader. But the transmission range is very small—usually less than an inch—and the radio waves don’t provide enough power for additional sensors. To overcome those limitations, researchers from MIT have developed new photovoltaic-powered sensors that work well with RFID chips.
The word “photovoltaic” literally means “voltage from light,” and refers to technology that can generate power directly from exposure to light. Most people have seen photovoltaic cells on battery-free calculators, which don’t require a large amount of power. In this case, the MIT researchers are using photovoltaic cells to add supplementary power to RFID devices. Enough additional power is provided to increase the transmission range of those RFID devices, and to allow the use of sensors for collecting data. The combination of photovoltaic cells and RFID chips could dramatically increase the lifespan of IoT (Internet of Things) devices, while also making them inexpensive enough to be disposable.
To achieve that, they had to utilize special perovskite photovoltaic cells. In comparison to traditional solar cells, perovskite photovoltaic cells cost just a few cents each and can be manufactured using roll-to-roll fabrication methods. They’re also thin, flexible, and transparent. They are less efficient than other solar cell types, but can be tuned for either indoor or outdoor light. But, because their cost is so low, it would be practical to integrate them into ultra-affordable environmental sensors. To demonstrate that feasibility, the MIT researchers created a prototype RFID circuit that can be used to monitor temperature. In the future, they plan to expand those capabilities with additional sensors.