Bendable energy-harvesting module with organic photovoltaic, rechargeable battery, and a-IGZO TFT charging electronics

This work presents an innovative bendable module for solar-energy harvesting. The module consists of a mechanically flexible organic photovoltaic device (OPV), a rechargeable battery, and an a-IGZO TFT charge-control circuit. The total thickness of the module is 1.1 mm. We present measurements of hardware implementations and simulations. On this basis, voltage converter schemes based on a charge pump in the flexible a-IGZO TFT technology are explored, to enhance the range of operation of the module, particularly under low-light conditions. All investigations and data are presented with focus on two variants of the energy harvesting module that differ in nominal output voltage and capacity: a 6 V variant with capacity of 14.4 mAh and a 24 V variant with capacity of 5.5 mAh. Under exposure to 1 sun, both can be charged in less than 4 hours.