Array of mini-graphene solar cells intermittently recharges storage capacitors powering a temperature sensor

Developing autonomous sensor systems that draw power from the ambient environment is a critical step for creating the Internet of Things. In this study, the authors built dozens of graphene-based solar cells, wire bonded them into standard packages, and characterized the current-voltage characteristics of each under illumination. Next, solar cells were connected in series to increase the output voltage. Three different sets of solar cells were used to charge three storage capacitors to the voltage levels required by our temperature sensor. The storage capacitors require only a few minutes to charge, yet power the sensor system for more than 24 hours without recharging. Using storage capacitors also eliminates the need for a typical power management chip and the commonly used rechargeable battery. As a result, one can lower the overall power consumed by the sensor system and significantly extend its useful life.