Chemical Doping Effects on CVD-Grown Multilayer MoSe₂ Transistor

Multilayer transition metal dichalcogenides (TMDs) potentially provide opportunities for large-area electronics, including flexible displays and wearable sensors. However, most TMDs suffer from a Schottky barrier (SB) and nonuniform defects, which severely limit their electrical performances. Here, a novel chemical doping scheme is presented using poly-(diketopyrrolopyrrole-terthiophene) (PDPP3T) to compensate the defects and SB of multilayer molybdenum diselenide (MoSe₂), exhibiting greatly enhanced electrical characteristics, including on-current (≈2000-fold higher) and photoresponsivity (≈10-fold larger) over the baseline MoSe₂ device. Based on comprehensive analysis using X-ray photoelectron spectroscopy, grazing incidence wide-angle X-ray diffraction, atomic force microscopy, and near-edge X-ray absorption of fine structure, it is shown that two mechanisms (dipole-induced and charge-transfer doping effects) account for such enhancements in the multilayer MoSe₂ device. The methodical generality of the strong n-doping behavior of multilayer MoSe₂ is further demonstrated by applying thiophene instead of PDPP3T.