The twist angle at van der Waals interfaces has emerged as a powerful degree of freedom for tailoring excitonic energy landscapes in two-dimensional semiconductors, yet how interlayer coupling and photoinduced dynamic dipole screening cooperatively govern excitonic responses remains elusive. Here, we directly investigate the twist-angle-dependent Coulomb-dominated excitonic effects in bilayer WS₂, including bandgap renormalization (BGR), exciton binding energy, recombination lifetime, and mobility. Femtosecond transient absorption spectroscopy reveals a twist-angle-tunable exciton binding energy from 265 to 336 meV; upon approaching the Mott transition threshold, BGR varies by over 100 meV and is most significant near-30°, where weakened interlayer coupling makes Coulomb interactions dominant. Moreover, the exciton lifetime and mobility are jointly dictated by the twist angle: strong interlayer coupling suppresses recombination while enhancing exciton mobility by threefold. This work integrates photoinduced screening with twist-angle engineering, establishing a unified picture of exciton many-body dynamics and offering guidance for high-performance excitonic devices.

Two-dimensional transition metal dichalcogenides (TMDs) are promising candidates for next-generation optoelectronics, but their performance is often constrained by intrinsic defects. Acid treatment has emerged as a powerful defect engineering strategy, dramatically boosting the photoluminescence (PL) quantum yield of these atomically thin semiconductors. This review systematically examines progress in acid-induced PL enhancement of TMDs over the past decade and distills the underlying mechanisms and ongoing controversies. A central theme is the ubiquitous trade-off: optical properties improve markedly, whereas electrical transport in field-effect transistors frequently degrades after treatment. This counterintuitive behavior is rationalized through a sulfur vacancy-mediated hopping transport model, which shows that the trade-off is an inherent consequence of defect manipulation rather than a side effect. Moving beyond this compromise, synergistic design rules for decoupling optical and electronic responses are critically assessed, with particular emphasis on the emerging use of Lewis acids for targeted property modulation. Finally, future research directions are outlined, including integrating machine learning with atomic-scale defect characterization, testing the generality of defect‑selective passivation across diverse defects, and advancing these strategies toward practical device applications.

Blue photodetectors are critical components for underwater wireless optical communication, high-resolution bioimaging, and environmental monitoring. However, there remains a need for more practical and energy-saving devices with facile synthesis and stable materials. Herein, we developed a blue photodetector featuring a unilateral Schottky junction on multilayer WS₂ decorated with Ag nanoparticles (Ag NPs). The synergistic cooperation of high-energy exciton from WS₂ and localized surface plasmon resonance (LSPR) induced by Ag NPs enhance responsivity and external quantum efficiency up to 244 mA/W and 74.7% under 405 nm with zero external bias, respectively. Ultrafast transient absorption spectroscopy directly reveals the LSPR effect significantly enhances the generation of high-energy excitons, providing a microscopic mechanism for the improvement. Critically, this device enables 128 × 128 resolution blue-light single-pixel imaging in both clear and turbid water, achieving a high peak signal-to-noise ratio (PSNR) of 25.5 dB. This work provides a new strategy for developing the self-powered underwater optical communication and high-visibility imaging technologies.

Artificial tetrachromatic vision significantly enhanced color discrimination by enabling the detection and spectral decoding of ultraviolet (UV) and visible wavelengths. Inspired by the butterfly visual system, we develop a tetrachromatic optoelectronic synapse utilizing monolayer WS₂ as the core element, effectively integrating sensing, memory, and processing capabilities. The constructed device demonstrates wavelength-sensitive synaptic excitatory behaviors under both visible and UV stimuli, successfully emulating key synaptic functions, including short-term potentiation (STP), long-term potentiation (LTP), and long-term depression (LTD), which achieves an ultralow power consumption of 2.28 aJ. An 8 × 8 retinal synapse array was constructed to achieve high-fidelity tetrachromatic image sensing and memory while enabling color discrimination. Furthermore, the image preprocessing is realized in the optoelectronic synapse array based on visual attention for color, which resulted in an enhancement of the recognition accuracy of the tetrachromatic image to over ~ 98%. This work has precipitated the development of next-generation neuromorphic vision systems that require UV–visible spectral intelligence.