On-Chip Illuminometer Using Open-Circuited Integrated Photovoltaic Cell for Internet of Things Application

This letter proposes an illumination detection method that employs the output voltage of an on-chip photovoltaic cell. Currently, photo-diode-based optical sensing is significant; however, the use of an open-circuited photovoltaic cell reduces the measurement setup component with the stabilized output at an order of hundreds of mV. This detection system comprises a photovoltaic cell and a comparator. The open-circuit voltage (
$V_{OC}$
) of the photovoltaic cell is compared to the reference voltage. These components are fully integrated with 0.18
$\mu$
m standard complementary metal-oxide semiconductor (CMOS) processed large-scale-integration (LSI) chips. The numerical simulation demonstrates that
$V_{OC}$
stabilizes under sufficient bulk quality and depends on the illumination conditions. A reference voltage of 550 mV is set in our results to determine whether the chip was under sunlight or room light, and the experimental measurements of
$V_{OC}$
demonstrate well-matched results and the feasibility of our proposed method.