  We present a new approach to ubiquitous sensing for indoor applications,
using high-efficiency and low-cost indoor perovksite photovoltaic cells as
external power sources for backscatter sensors. We demonstrate wide-bandgap
perovskite photovoltaic cells for indoor light energy harvesting with the
1.63eV and 1.84 eV devices demonstrate efficiencies of 21% and 18.5%
respectively under indoor compact fluorescent lighting, with a champion
open-circuit voltage of 0.95 V in a 1.84 eV cell under a light intensity of
0.16 mW/cm2. Subsequently, we demonstrate a wireless temperature sensor
self-powered by a perovskite indoor light-harvesting module. We connect three
perovskite photovoltaic cells in series to create a module that produces 14.5
uW output power under 0.16 mW/cm2 of compact fluorescent illumination with an
efficiency of 13.2%. We use this module as an external power source for a
battery-assisted RFID temperature sensor and demonstrate a read range by of 5.1
meters while maintaining very high frequency measurements every 1.24 seconds.
Our combined indoor perovskite photovoltaic modules and backscatter
radio-frequency sensors are further discussed as a route to ubiquitous sensing
in buildings given their potential to be manufactured in an integrated manner
at very low-cost, their lack of a need for battery replacement and the high
frequency data collection possible.
