Visual adaptation that can autonomously adjust the response to light stimuli is a basic function of artificial visual systems for intelligent bionic robots. To improve efficiency and reduce complexity, artificial visual systems with integrated visual adaptation functions based on a single device should be developed to replace traditional approaches that require complex circuitry and algorithms. Here, we have developed a single two-terminal opto-sensor based on multilayer γ-InSe flakes, which successfully emulated the visual adaptation behaviors with a new working mechanism combining the photo-pyroelectric and photo-thermoelectric effect. The device can operate in self-powered mode and exhibit good human-eye-like adaptation behaviors, which include broadband light-sensing image adaptation (from ultraviolet to near-infrared), near-complete photosensitivity recovery (99.6%), and synergetic visual adaptation, encouraging the advancement of intelligent opto-sensors and machine vision systems.
Transition-metal dichalcogenides exhibit strong photon absorption characteristics in the band nesting region (denoted as C-exciton) due to intrinsic van Hove singularities despite being atomically thin. However, because of unique parallel band structure and ineluctably unfavorable recombination process, only a small fraction of the hot carriers from C-excitons are converted into optically active band-edge excitons via inherent relaxation-paths. The resultant photoluminescence quantum yield (PLQY) is severely suppressed for the resonant excitation of Cexciton. To overcome this limitation, we have designed double type-I band alignments to construct a band nesting bypass in a monolayer WS 2 /CdS quantum dot heterostructure for cooling the C-excitons. Transient optical measurements confirmed that the hot carriers from the C-excitons were effectively transferred from WS 2 to CdS with an efficiency of 50% and subsequently back to the WS 2 band-edge to form A-excitons over an ultrafast subpicosecond time scale, accompanied by a record high PLQY of ∼11.1% for near-resonance C-exciton excitation.
Improving the stability of lead iodide (PbI2), especially photostability, is in crucial demand for the realization of application‐level optoelectronic devices. In this regard, deposition of organic polymers on PbI2 as a protective layer is a common strategy to improve its stability, but polymers with low thermal conductivity generally cannot produce the desired effect. Herein, a novel strategy is proposed for improving the photostability of PbI2 at different excitation wavelengths, including 320, 405, and 532 nm, via constructing type‐I heterostructure with ZnO with high thermal conductivity. In addition, due to the type‐I band alignment between PbI2 and ZnO, the photogenerated carriers in ZnO can be transferred to PbI2, resulting in a nearly eightfold photoluminescence enhancement of PbI2 under 320 nm laser excitation. The ZnO as a protective layer forming type‐I heterostructure is evidenced as a feasible strategy for enhancing the photostability and photoluminescence of PbI2, facilitating the development of practical applications.
Lead Iodide Stability
In article number http://doi.wiley.com/10.1002/adpr.202000183, Yuanzheng Li, Weizhen Liu, and co‐workers propose a novel and feasible strategy for improving the photostability of PbI2 via constructing type‐I heterostructures with ZnO with high thermal conductivity. Besides, due to the type‐I band alignment between ZnO and PbI2, the photoluminescence intensity of PbI2 is enhanced to nearly 8‐fold under 320 nm laser excitation.
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