  Billions of everyday objects could become part of the Internet of Things
(IoT) by augmentation with low-cost, long-range, maintenance-free wireless
sensors. Radio Frequency Identification (RFID) is a low-cost wireless
technology that could enable this vision, but it is constrained by short
communication range and lack of sufficient energy available to power auxiliary
electronics and sensors. Here, we explore the use of flexible perovskite
photovoltaic cells to provide external power to semi-passive RFID tags to
increase range and energy availability for external electronics such as
microcontrollers and digital sensors. Perovskites are intriguing materials that
hold the possibility to develop high-performance, low-cost, optically tunable
(to absorb different light spectra), and flexible light energy harvesters. Our
prototype perovskite photovoltaic cells on plastic substrates have an
efficiency of 13% and a voltage of 0.88 V at maximum power under standard
testing conditions. We built prototypes of RFID sensors powered with these
flexible photovoltaic cells to demonstrate real-world applications. Our
evaluation of the prototypes suggests that: i) flexible PV cells are durable up
to a bending radius of 5 mm with only a 20 % drop in relative efficiency; ii)
RFID communication range increased by 5x, and meets the energy needs (10-350
microwatt) to enable self-powered wireless sensors; iii) perovskite powered
wireless sensors enable many battery-less sensing applications (e.g.,
perishable good monitoring, warehouse automation)
