A negative photoconductivity photodetector based on two-dimensional Nb₃Cl₈

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Negative photoconductivity (NPC) photodetectors are explored for energy-efficient photodetection.
• Two-dimensional (2D) materials are ideal for NPC due to surface properties and tunable bandgaps.
• 2D Nb3Cl8, a metal halide with a kagome lattice, shows potential for NPC due to defect formation.

Purpose of the Study:

• To investigate the NPC characteristics of 2D Nb3Cl8.
• To fabricate and characterize Nb3Cl8-based photodetectors.
• To understand the underlying mechanism of NPC in Nb3Cl8.

Main Methods:

• Synthesis of Nb3Cl8 single crystals using chemical vapor transport (CVT).
• Fabrication of field-effect transistors (FETs) using Nb3Cl8.
• Characterization of photodetector performance, including responsivity and NPC behavior across a wide wavelength range (400-1050 nm).

Main Results:

• Nb3Cl8 FETs demonstrated electron mobility of 4.24 × 10^-3 cm^2 V^-1 s^-1 and a high on/off ratio (1.42 × 10^4).
• Nb3Cl8 photodetectors exhibited consistent NPC behavior over a broad spectral range (400-1050 nm).
• A high responsivity of 156.82 mA W^-1 was recorded at 400 nm.

Conclusions:

• The NPC phenomenon in Nb3Cl8 is attributed to defect-induced carrier trapping within the bandgap.
• Nb3Cl8 shows significant promise as an efficient material for energy-saving photodetectors.
• The study highlights Nb3Cl8's potential for diverse optoelectronic applications.