In this article, we propose a novel approach to demonstrate tunable photoinduced carrier transport of a few-layered black phosphorus (BP) field-effect transistor (FET) with extended air stability using a "light-sensitized ultrathin encapsulated layer". Titanium suboxide (TiOx) ultrathin film (approximately 3 nm), which is an amorphous phase of crystalline TiO2 and can be solution processed, simultaneously exhibits the unique dual functions of passivation and photoinduced doping on a BP FET. The photoinduced electron transfer at TiOx/BP interfaces provides tunable n-Type doping on BP through light illumination. Accordingly, the intrinsic hole-dominated transport of BP can be gradually tuned to the electron-dominated transport at a TiOx/BP FET using light modulation, with enhanced electron mobility and extended air stability of the device. The novel device structure consisting of a light-sensitized encapsulated layer with controllable and reversible doping through light illumination on BP exhibits great potential for the future development of stable BP-based semiconductor logic devices or optoelectronic devices.
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