N‐Type Doping and Passivation of Black Phosphorus Using Pentacene for Infrared Polarization‐Sensitive Photodetection and Imaging

Abstract

Abstract Few‐layer black phosphorus (FL‐BP) shows great potential in infrared polarization‐sensitive photodetection due to its narrow bandgap and strong in‐plane anisotropy. However, FL‐BP is easy to be oxidized and degraded, which severely restricts its applications. Herein, a simple and scalable in situ interfacial passivation method based on pentacene film is reported to enhance the ambient stability of FL‐BP as well as achieve n‐type doping for improved polarization‐sensitive photoimaging. High crystal quality FL‐BP flakes with intrinsic anisotropy are prepared by electrochemical exfoliation. The morphology and Raman spectra of FL‐BP/pentacene exhibit excellent stability 28 days after passivation. In addition, the hole mobility is significantly enhanced and dark current is substantially suppressed due to the interfacial passivation and n‐type doping effect. The FL‐BP/Pentacene based photodetector shows a broadband response from visible to near‐infrared with good stability. The photoresponsivity under 915 nm illumination is calculated as 2.2 mA W−1 with an anisotropy ratio of 1.29. Furthermore, the polarization imaging under the irradiation at zigzag and armchair directions directly reveals the strong infrared polarization‐sensitive imaging capability of FL‐BP/pentacene. This work also opens up new avenues to enhance the photoresponse and stability of various optoelectronics based on similarly unstable 2D materials.

Keywords

• electrochemical exfoliation
• few‐layer black phosphorus
• infrared polarization‐sensitive photodetector
• interface engineering
• passivation