High-Performance Ultraviolet Photodetectors Enabled by van der Waals Schottky Junction Based on TiO2 Nanorod Arrays/Au-Modulated Ti3C2Tx MXene

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 TiO2 nanorod arrays/Ti3C2Tx MXene van der Waals (vdW) Schottky junction by all-solution process technique is reported. The Ti3C2Tx 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 Ti3C2Tx, 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 TiO2 and oxygen) and reverse pyroelectric effect are largely eliminated. As a result, the responsivity and specific detectivity of the device with FTO/TiO2 nanorod arrays/Ti3C2Tx/Au structure reach 1.95 x 10(5) mA W-1 and 4.3 x 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.