Integration of an organic photovoltaic (PV) with carbon-based supercapacitors (SCs) into a system for solar energy harvesting and storage is interesting for off-grid applications such as mobile electronics and sensor systems. Presented here is a conversion and control circuit (CC) on a flexible polyimide substrate in an integrated flexible energy harvesting and storage device compatible with roll-to-roll manufacturing (R2R). The CC is capable of PV max power-point tracking, DC-DC voltage boost of the PV output across a bank of four SCs, and charge balancing across the bank of SCs. This system is compared to a conventional direct connection between the PV and the SCs. More energy can be harvested from the PV and stored in the SC bank when using the CC to drive the PV at peak power, boost the output voltage, and balance it across serial connection of SCs. Finally, the CC, PV, and SCs are mounted to a 3D printed substrate and circuit which is used to power a wearable sensor. Due to these benefits and ability to be integrated with R2R, the presented CC provides a practical means of improving wearable solar energy harvesting and storage systems. (C) The Author(s) 2018. Published by ECS.