Conducting polymer based hybrid cells for concurrent solar energy harvesting and charge storage

Due to the intermittent nature of solar energy availability, often an energy storage element such as a battery or supercapacitor is required to store the energy from a solar cell. The combination of a separate solar cell and an energy storage device is not usually suitable for small and compact electronic circuits with small footprints. Although various hybrid solar cell-supercapacitor devices have been studied before, the majority of them are two cells in one package with one electrode being shared between the two cells. We have designed and studied a new class of two-terminal hybrid electrochemical cells made of conducting polymer (e.g., polyaniline) composites with porous electrodes. In one design, a polymer film with embedded dye molecules has been used as a photoactive electrode in a supercapacitor presenting open circuit voltage changes up to 430 mV under illumination. In another design, the conducting polymer was employed in the electrolyte of the cell making a supercapacitor with the capability of harvesting light through the electrolyte. Voltages as high as 138 mV were achieved in the new device. Due to the storage property, the voltage drop 10 min after the secession of light was ~15 mV. While the fabrication of devices with the photoactive gel is easier, the higher efficiency in thin-film devices is more promising. Further development of two-terminal hybrid cells can open doors for designing compact and self-powered wireless sensors for various applications, including wearable electronics.