Vertically Integrated Energy Device Sharing the Electrode of an Organic Photovoltaic Cell and a Silver–Zinc Rechargeable Battery

We propose a highly efficient, vertically integrated energy device (VIED) that combines an organic photovoltaic cell (OPV) with a silver–zinc secondary battery (SZB). Most integrated energy devices to date have been constructed by simply connecting individual devices to conductors or by having devices share a collector (the four-electrode structure). Researchers have reported devices that share core components to achieve high-efficiency and low device volume (the three-electrode structure). However, their energy densities and overall efficiencies are relatively low due to the limited capacity and voltage compatibility of energy storage devices. In this study, we used a silver electrode as the shared component to serve three roles simultaneously (the cathode of the OPV, the electrical connector, and the cathode of the SZB). We designed a highly efficient OPV using a novel light absorbing material with controlled crystallinity and metal-based interconnecting layers, thereby improving its fill factor and power conversion efficiency. Moreover, we matched the electrical characteristics of the OPV and SZB by selecting the appropriate active ions in the electrolyte for SZB to enhance the actual power conversion efficiency of the OPV within the VIED. The designed VIED was reversibly operated for up to 20 cycles by charging with solar power and discharging with a constant current. The overall efficiency of the designed device was 11.2%. This is the highest value achieved among OPV-based integrated energy devices to date.