Langmuir–Blodgett fabrication of large-area black phosphorus-C60 thin films and heterojunction photodetectors

Abstract

Black phosphorus (BP) has emerged as a promising two-dimensional (2D) semiconductor for applications in electronics, optoelectronics, and energy storage. As is the case for many 2D materials, the fabrication of large-area BP thin films remains a considerable challenge. Here, we report the assembly of BP nanosheets into compact thin films using the Langmuir–Blodgett (LB) technique. The overlapping stacking between BP nanosheets is suppressed when the nanosheets are surrounded by fullerene C₆₀ molecules due to physisorption. This allows for the fabrication of large-area BP films (20 mm × 18 mm) with a homogenous nanosheet distribution and negligible oxidation. The fabricated films show measurable absorption up to 2.3 μm. We use these films as active layers to demonstrate mm-sized BP heterojunction photodetectors with mA W⁻¹ scale responsivities from the visible to the near-infrared. Photodetector internal quantum efficiencies at 660 nm and 808 nm are 5% and 1%, respectively.