Xinyue Liu

Electro‐optical control of spectra at the nanoscale, even at the single‐nanoparticle (NP) level, is crucial in the miniaturization and multifunctionality of optoelectronic devices. Mie resonance‐based dielectric nanostructures provide an intriguing paradigm to boost the light‐matter interaction. This makes them strong candidates for optoelectronic applications. However, achieving narrowband electrical tuning based on a single dielectric NP remains challenging due to the slight change of refractive index caused by carrier injection. Herein, a new type of nano‐resonator is reported to optimize the Mie‐exciton Fano coupling. It consists of silicon (Si) NPs placed on a tungsten disulfide (WS ₂ ) /hexagonal boron nitride (hBN) hetero‐nanogap. The image magnetic mode across the hetero‐nanogap generated by Si NPs on the mirror enables effective spatial overlapping with WS ₂ excitonic resonance. It also maximizes the electrostatic doping effect on spectral tailoring at the excitonic wavelength. Owing to strong Mie‐exciton coupling, the scattering intensity can be electrically controlled with a modulation depth even larger than that of plasmonic counterparts. Furthermore, Si NPs exhibit much lower heat loss than plasmonic NPs. Importantly, Si NPs on WS ₂ /hBN nanogap with broadband colorful scattering but narrowband electrical tuning will act as bi‐functional nanopixels loading dynamic optical signals. This platform has potential applications in information encryption and integrated active optical devices.

The applications of 2D material photodetectors in extensive fields, including imaging, health monitoring, tracking, logic operation, ultraviolet monitoring, communications, automatic driving, and acoustic signal detection, have been introduced.

Photodetectors based on two-dimensional van der Waals (2D vdW) heterostructures with high detectivity and rapid response have emerged as promising candidates for next-generation imaging applications. However, the practical application of currently studied 2D vdW heterostructures faces challenges related to insufficient light absorption and inadequate separation of photocarriers. To address these challenges, we present a sandwiched WS₂/MoTe₂/WS₂ heterostructure with a completely depleted interlayer, integrated on a mirror electrode, for a highly efficient photodetector. This well-designed structure enhances light-matter interactions while facilitating effective separation and rapid collection of photocarriers. The resulting photodetector exhibits a broadband photoresponse spanning from deep ultraviolet to near-infrared wavelengths. When operated in self-powered mode, the device demonstrates an exceptional response speed of 22/34 μs, along with an impressive detectivity of 8.27 × 10¹⁰ Jones under 635 nm illumination. Additionally, by applying a bias voltage of -1 V, the detectivity can be further increased to 1.49 × 10¹² Jones, while still maintaining a rapid response speed of 180/190 μs. Leveraging these outstanding performance metrics, high-resolution visible-near-infrared light imaging has been successfully demonstrated using this device. Our findings provide valuable insights into the optimization of device architecture for diverse photoelectric applications.

Two-dimensional (2D) gallium selenide (GaSe) holds great promise for pioneering advancements in photodetection due to its exceptional electronic and optoelectronic properties. However, in conventional photodetectors, 2D GaSe only functions as a photosensitive layer, failing to fully exploit its inherent photosensitive potential. Herein, we propose an ultrasensitive photodetector based on out-of-plane 2D GaSe/MoSe₂ heterostructure. Through interfacial engineering, 2D GaSe serves not only as the photosensitive layer but also as the photoconductive gain and passivation layer, introducing a photogating effect and extending the lifetime of photocarriers. Capitalizing on these features, the device exhibits exceptional photodetection performance, including a responsivity of 28 800 A/W, specific detectivity of 7.1 × 10¹⁴ Jones, light on/off ratio of 1.2 × 10⁶, and rise/fall time of 112.4/426.8 μs. Moreover, high-resolution imaging under various wavelengths is successfully demonstrated using this device. Additionally, we showcase the generality of this device design by activating the photosensitive potential of 2D GaSe with other transition metal dichalcogenides (TMDCs) such as WSe₂, WS₂, and MoS₂. This work provides inspiration for future development in high-performance photodetectors, shining a spotlight on the potential of 2D GaSe and its heterostructure.

Silicon nanoparticles (Si NPs) supporting Mie resonances exhibit vivid structural colors on the subwavelength scale. For future wearable devices, next generation Si-based optical units need to be dynamic and stretchable for display, sensing, or signal processing required by human-computer interaction. Here, by utilizing the distance-sensitive electromagnetic coupling of Mie resonances, we maximize the active tuning effect of Si NP-based structures including dimers, oligomers, and NPs on WS₂, which we called Si nanopixels. Through the optical tweezers-assisted printing of Si nanopixels, patterns can be formed on arbitrary flexible substrates. The strain-sensitive tuning of scattering spectra indicates their promising application on strain sensing of various stretchable substrates via a simple "spray and test" process. In the case of Si nanopixels on polydimethylsiloxane (PDMS), local strains around 1% can be detected by a scattering measurement. Moreover, we demonstrate that the scattering intensity variation of Si nanopixels printed on wrinkled tungsten disulfide (WS₂) is pixel-dependent and wavelength-dependent. This property facilitates the application of information encryption, and we demonstrate that three barcodes can be independently encoded into the R, G, and B scattering channels through ternary logic represented by the strain-tuning effects of scattering.