This paper presents a fully integrated CMOS light-powering system, integrating CMOS photovoltaic cell and energy harvesting interface, for batteryless internet of things (IoT). The CMOS photovoltaic cell employs deep N-well (DNW) based structure to improve the light-electric conversion efficiency. The energy harvesting interface utilizes a fully integrated two-stage switched-capacitor dc-dc converter to provide an appropriate output voltage for load circuits. It provides 1 V and 0.9-1.1 V output under light load and heavy load, respectively. The chip is designed and fabricated by 180-nm CMOS process, without using any off-chip components, except a storage capacitor for testing. The experimental results demonstrate that the proposed 1mm x 2mm fully integrated light-powering system can periodically provide 0.9 V to 1.1 V output voltage to power 1-mA loading circuit. The proposed interface achieves 70 percent peak-efficiency at 1 μA and higher than 60 percent efficiency over 0.5 μA to 2 μA loading currents.