No abstract

Facile, convenient and low-cost processes were used to fabricate self-powered ZnO nanorod array ultraviolet photodetectors with CuSCN/rGO hole-transport bilayers. The device performance with a functionalized graphene layer was greatly improved.

Two-dimensional transition metal carbides and nitrides (MXenes) show tremendous potential for optoelectronic devices due to their excellent electronic properties. Here, a high-performance ultraviolet photodetector based on TiO 2 nanorod arrays/Ti 3 C 2 T x MXene van der Waals (vdW) Schottky junction by allsolution process technique is reported. The Ti 3 C 2 T x MXene modulated by the Au electrode increases its work function from 4.41 to 5.14 eV to form a hole transport layer. Complemented by the dangling bond-free surface of Ti 3 C 2 T x , the Fermi-level pinning effect is suppressed and the electric-field strength of the Schottky junction is enhanced, which promotes charge separation and transport. After applying a bias of −1.5 V, the photovoltaic effect is favorably reinforced, while the hole-trapping mechanism (between TiO 2 and oxygen) and reverse pyroelectric effect are largely eliminated. As a result, the responsivity and specific detectivity of the device with FTO/TiO 2 nanorod arrays/ Ti 3 C 2 T x /Au structure reach 1.95 × 10 5 mA W −1 and 4.3 × 10 13 cm Hz 1/2 W −1 (370 nm, 65 mW cm −2 ), respectively. This work provides an effective approach to enhance the performance of photodetectors by forming the vdW Schottky junction and choosing metal electrodes to modulate MXene as a suitable charge transport layer.

In this paper, we demonstrate a new heterojunction ultraviolet (UV) photodetector in a superstrate configuration, i.e. glass/FTO/ZnO NRs/rGO/Au, constructed via the dip-coated method to form reduced graphene oxide (rGO) layer on the surface of ZnO nanorod arrays (NRs). The rGO compensates for surface oxygen vacancies by the oxygen-containing groups and improves the crystal properties of ZnO NRs after annealing. Furthermore, the carrier mobility and work function are effectively increased after Au doping. Under UV irradiation, the electron–hole pairs generated by ZnO NRs are separated with bias voltage, and the electrons and holes are collected via fluorine-doped tin dioxide (FTO) and rGO/Au, respectively. The rGO acts as a hole transport layer, which reduces the recombination of carriers and increases the current density, giving rise to a higher responsivity (67.48 A W−1 at −1.5 V bias) than pure ZnO NRs photodetectors.