Controllably grown single-crystal films as flexoelectric nanogenerators for continuous direct current output

Until now, conventional nanogenerators could only produce electric pulses with relatively low-power densities. Herein, we invent a novel controllable growth technique for two-dimensional (2-D) cuprous oxide (p-Cu 2 O) single-crystal films, and on this basis, a new concept of 2-D single-crystal film flexoelectric nanogenerators (FENGs) are rationally designed and constructed for the first time, which has the characteristics of long-range order lattice, few grain boundaries and defects. More importantly, the accumulated built-in polarization potential in the bent 2-D p-Cu 2 O single-crystal film FENGs is in the same orientation as the output electricity, resulting in the first nanogenerator that can output continuous and stable electric signals with high voltage (V oc of 2.8 V), current (J sc of 11.5 μA·cm −2 ) and power density (14.4 μW·cm −2 ), exhibiting great practical application potential for power generation and motion capture. This research breaks new ground and establishes a precedent for high-performance and continuous-output nanogenerators, as well as smart wearable sensors.