Printed Kirigami Organic Photovoltaics for Efficient Solar Tracking

The rapid surge in the power conversion efficiencies (PCEs) of organic photovoltaics (OPVs) calls for a simple and efficient solar tracking strategy to maintain normal incidence of light and fully use the solar energy. Here this study proposes a new solar tracking approach based on kirigami by taking the advantage of the paper-like OPVs made on flexible substrates. The kirigami pattern is judicially designed to form three separate regions of beams, hinges, and devices. The stretching force is applied to beams, which cause out-of-plane deformation of the hinges, rotating the device connected to the hinges and maintaining nearly 100% optical coupling efficiency. Electrospray is used to print active layers on the pre-cut kirigami substrates. The all-printed kirigami OPVs achieve the highest PCE of 14.15%. Large-area kirigami OPVs (0.62 cm(2)) demonstrate PCEs up to 10.19%. The kirigami OPVs are mechanically robust, showing no appreciable decrease in performance after a 20 000-cycle stretching. This kirigami structure provides possibilities to customize the shapes of the device region to achieve more functions such as ventilation and decoration. The kirigami OPVs show satisfactory PCEs, effective solar tracking and versatile design possibilities, powerfully demonstrating the thin, light and flexible feature of OPVs.