Sensitive and Ultrabroadband Phototransistor Based on Two‐Dimensional Bi2O2Se Nanosheets

Abstract Bi 2 O 2 Se, a high‐mobility and air‐stable 2D material, has attracted substantial attention for application in integrated logic electronics and optoelectronics. However, achieving an overall high performance over a wide spectral range for Bi 2 O 2 Se‐based devices remains a challenge. A broadband phototransistor with high photoresponsivity ( R ) is reported that comprises high‐quality large‐area ( ≈ 180 µm) Bi 2 O 2 Se nanosheets synthesized via a modified chemical vapor deposition method with a face‐down configuration. The device covers the ultraviolet (UV), visible (Vis), and near‐infrared (NIR) wavelength ranges (360–1800 nm) at room temperature, exhibiting a maximum R of 108 696 A W −1 at 360 nm. Upon illumination at 405 nm, the external quantum efficiency, R , and detectivity ( D* ) of the device reach up to 1.5 × 10 7 %, 50055 A W −1 , and 8.2 × 10 12 Jones, respectively, which is attributable to a combination of the photogating, photovoltaic, and photothermal effects. The devices reach a −3 dB bandwidth of 5.4 kHz, accounting for a fast rise time (τ rise ) of 32 µs. The high sensitivity, fast response time, and environmental stability achieved simultaneously in these 2D Bi 2 O 2 Se phototransistors are promising for high‐quality UV and IR imaging applications.