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-Cu₂O) 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-Cu₂O 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.