Synthesis Techniques, Optoelectronic Properties, and Broadband Photodetection of Thin‐Film Black Phosphorus

Abstract Black phosphorus (BP), a van der Waals (vdW) layered material, has been intensively studied in recent years since the rediscovery of its thin‐film form in 2014. It is considered as a promising material for mid‐infrared (MIR) photodetection, due to its intrinsic narrow bandgap, tunable band properties, decent optical absorption, high room‐temperature mobility, and high compatibility with silicon‐based technology. Here, the recent advances in the synthesis techniques, the novel optoelectronic properties, and applications of thin‐film BP flake in MIR photodetection are reviewed. Over 17 synthesis techniques of BP films, as well as their merits and drawbacks, are summarized and discussed. The recently discovered strain‐, electric‐field‐, and chemical‐doping‐induced bandgap tuning effects in BP effectively extend its optical absorption cutoff wavelength into regime with longer wavelength (>4 µm). In addition, the establishment of BP‐based vdW heterostructures paves a new way to design novel high‐performance MIR photodetectors. BP MIR photodetectors enabled by various photocurrent generation mechanisms (photoconductive, photogating, and photovoltaic effect) and device configurations (transistor‐type, waveguide‐coupled, Schottky‐junction‐type, and heterojunction‐type devices) are summarized and compared.