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Vertical semiconductor van der Waals heterojunctions are essential for fabricating high-performance photodetectors. However, the range of the spectral response and defect states of semiconductor materials are two critical factors affecting the performance of photodetectors. In this work, the spectral response range of WS2 was changed through WS2 band gap regulation, and a self-powered vertical WS1.08Se0.92/Si heterojunction photodetector with MXene electrode was prepared by synthesizing WS1.08Se0.92 film on Si substrate and vertically stacking Ti3C2T x MXene on the film. Due to the electron collection of MXene and the wonderful junction quality of WS1.08Se0.92/Si, the photodetector can detect near-infrared light in the range of 980–1310 nm, which exceed the detection limit of WS1.08Se0.92. And the device had high sensitivity in the broadband. The responsivity was 4.58 A W−1, the specific detectivity was 4.58 × 1011 Jones, the on/off ratio was 4.95 × 103, and the fast response time was 9.81/9.03 μ s. These properties are superior to previously reported WS2-based photodetectors. Vertical structure, Energy band tuning, and MXene electrode provide a new idea for preparing broadband high-performance and self-powered photodetector. [ABSTRACT FROM AUTHOR]

Ferroelectric polarization plays important roles in catalytic reactions, but the mechanism is still under debate. In this work, 2D ferroelectric MIrSn2S6 is systematically investigated for revealing the effects of ferroelectric polarization on the oxygen evolution reaction (OER) based on density-functional-theory (DFT) calculations. We find that: (1) the adsorption configurations of intermediates, protons, and water strongly depend on the polarization, which in turn affects their bonding patterns and adsorption energies; (2) the paraelectric (PE) state generally shows the highest OER activity (overpotential = 0.54 V) due to its most favorable free energy change; and (3) the capacitances are varied under different polarization states, which affects the reaction kinetics. Our findings illustrate the full picture of the OER process under different polarizations, which may provide insightful understanding on the ferroelectric-enhanced catalytic activity and guide the design of novel ferroelectric catalysts. [ABSTRACT FROM AUTHOR]