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

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.