Electrical modulation of luminescence is significant to modern light-emitting devices. Monolayer transition metal dichalcogenides are emerging direct-bandgap luminescent materials with unique excitonic properties, and the multiple exciton complexes provide new opportunities to modulate the property of luminescence in atomically thin semiconductors. Here, we report an electrical control of exciton emission in the oscillator strength and spatial distribution of excitons in a monolayer WS₂. Effective modulation of excitonic emission intensity with a degree of modulation of ~ 92% has been demonstrated by an electric field at room temperature. The spatial carrier redistribution tuned by a lateral electric field results in distinct excitonic emission patterns by design. The modulation approach to exciton oscillator strength and distribution provides an efficient way to investigate the exciton diffusion dynamics and to construct electrically tunable optoelectronic devices.

Lead telluride (PbTe) is one of the reliable candidates for infrared (IR) optoelectronics with optimum band-gap as well as excellent photoelectric properties. Great interests had been paid on the growth and device applications with PbTe for the development of high-performance IR photodetectors especially those working in the near-infrared regime. Although a great deal of effort had been made to prepare PbTe nanostructures for miniaturized detectors, it is difficult to synthesize high-quality two-dimensional (2D) PbTe crystals due to its rock-salt non-layered structure. Herein, a facile strategy for controllable synthesis of ultrathin crystalline PbTe nanosheets by van der Waals epitaxy is reported. With an optimized growth temperature, which determines the morphology transit from triangular pyramid islands to regular square 2D planars, PbTe nanosheets in lateral size of tens of microns with thickness down to ~ 7 nm are achieved. Meanwhile, ultrasensitive near-infrared detectors (NIRDs) based on the as-grown 2D PbTe nanosheets have been demonstrated with an ultrahigh responsivity exceeding 3,847 A/W at the wavelength of 1,550 nm under room temperature. Our approach demonstrates that 2D PbTe nanosheets have great latent capacity of developing high-performance miniaturized IR optoelectronic devices.