From nanofibers to ordered ZnO/NiO heterojunction arrays for self-powered and transparent UV photodetectors
Uniformly aligned electrospun nanofiber arrays are important building blocks for high-performance functional devices and device arrays. However, it remains a challenge to prepare perfectly aligned and large area nanofiber arrays using common electrospinning. In this work, a modified electrospinning method utilizing three assisted electrodes for nanofiber collection was proposed to achieve uniformly aligned and millimeter-long ZnO and NiO nanofiber arrays (more than 90% of nanofibers aligned to within ±4° of the desired direction), which were further fabricated into ZnO/NiO heterojunction arrays with a density of 106 cm−2. Photodetectors (PDs) based on the as-prepared ZnO/NiO heterojunction arrays exhibited excellent ultraviolet (UV) selective and self-powered detection properties because of the properly matched energy bands of ZnO and NiO. A maximum responsivity of 0.415 mA W−1 and a short rise/decay time of 7.5 s/4.8 s at 0 V bias of the device markedly outstripped the reference ZnO nanofiber array device. The three-assisted-electrode electrospinning method of this work offers new chances in novel nanostructure design and high-performance device fabrication.