ABSTRACT Broadband photodetectors are essential for emerging applications such as intelligent vision, optical communication, and autonomous sensing. However, conventional multispectral photodetectors often require external spectral‐selection optics or rely on architectures with fixed spectral functionality, limiting electrical reconfigurability and adaptive multifunctionality. Here, we report a bias‐tunable photodetector based on a vertical WSe 2 /GaN van der Waals heterostructure formed by integrating multilayer WSe 2 with freestanding GaN films. Benefiting from the complementary absorption of GaN and WSe 2 , the photodetector exhibits a broadband photoresponse from 300 to 900 nm. More importantly, it demonstrates a bias‐switchable dual‐mode operation: under reverse bias, the device operates as a ultraviolet (UV)‐selective photodetector, whereas under forward bias it switches to broadband detection. This behavior originates from the interplay between bias‐modulated asymmetric valence‐band offsets and spatially selective light absorption. Furthermore, the vertical configuration and type‐II band alignment significantly shorten the carrier transport path and enables ultrafast carrier extraction. As a result, the device achieves an ultra‐low dark current (∼10 −12 A) and fast rise/decay times of 34/37 µs, nearly three orders of magnitude faster than lateral heterojunction counterparts. This work elucidates the physics of bias‐dependent carrier transport in vertical WSe 2 /GaN heterojunctions and establishes a versatile platform for adaptive, multifunctional, and highly integrated optoelectronic devices.
Metal nanoclusters have garnered significant research interest over the past two decades due to their unique photochemical properties. Herein, we synthesize Au 25 nanoclusters with various previously unused surface ligands. By systematically comparing their photoinitiation, photoluminescence, and photothermal effects, combined with comprehensive analysis of prior research findings, we elucidated a comprehensive, systematic structure‐activity relationship between ligand structure and nanocluster photochemistry. Notably, a new Au 25 (S‐Ph‐CF 3 ) 18 − (HS‐Ph‐CF 3 : 4‐trifluoromethyl‐benzenethiol) demonstrates exceptional performance across all the three photochemical processes, particularly in photoluminescence. It exhibits remarkable near‐infrared (NIR‐II) solid‐state fluorescence quantum yield of 10–13% at 1100 nm wavelength under room temperature, representing a competitive value among related materials to date at this wavelength range, and it also displays a high photothermal conversion efficiency of 56.2%. In terms of photoinitiation, Au 25 (S‐Ph‐CF 3 ) 18 − not only maintains the original printing sensitivity during two‐photon initiation, it also produces finer structures with enhanced formability. Single‐crystal X‐ray diffraction analysis reveals six distinct π···π stacking interactions between the thiophenol ligands in Au 25 (S‐Ph‐CF 3 ) 18 − , which effectively suppress intramolecular vibrational and rotational motions, leading to the enhanced quantum yield. This study systematically investigates ligand‐engineered Au 25 nanoclusters, providing in‐depth insights into their different photochemical characteristics. Furthermore, it develops a fluorine‐containing gold nanocluster with superior integrated optical properties.
Short‐wave infrared (SWIR) photodetectors operating at the telecommunication bands are indispensable for optical interconnects and secure communication, yet low‐cost alternatives to epitaxial infrared semiconductors remain scarce. Herein, a 0D/2D mixed‐dimensional van der Waals phototransistor is demonstrated by integrating HgTe quantum dots (QDs) with a WSe 2 channel. Benefiting from the type‐I nested band alignment, photoelectrons are trapped within the QDs to form a negative photogate, whereas photo‐holes are injected into the p‐type WSe 2 channel, yielding a pronounced photogating gain that is further amplified under negative gate bias. The device delivers high responsivities of 2858 and 2337 A W − 1 at 1310 and 1550 nm, respectively. The peak specific detectivity derived from flicker‐noise spectra reaches 5.31 × 10 10 Jones at 1310 nm, while the shot‐noise‐limited detectivity is 4.37 × 10 12 Jones. Leveraging the synchronous visible‐to‐SWIR photoresponse, a dual‐channel encrypted optical communication scheme is further realized, in which a 635 nm key channel delivers time‐dependent permutation rules while a 1310 nm channel transmits American Standard Code for Information Interchange‐encoded data enabling real‐time decryption of “SCNU”. This work establishes a viable route toward low‐cost, gate‐tunable SWIR photodetectors and highlights the potential of 0D/2D heterojunctions for externally encoded dual‐wavelength optical signaling with software‐assisted decoding.
The growing demand for outdoor, automotive, virtual reality (VR), and augmented reality (AR) displays has stimulated extensive research into light sources capable of high‐luminance operation. Among emerging display technologies, quantum‐dot light‐emitting diodes (QLEDs) are particularly attractive because of their high color purity, widely tunable emission, high efficiency, and compatibility with solution‐based fabrication and patterning. However, the realization of stable high‐luminance full‐color QLED displays remains limited primarily by the inferior performance of blue devices. The wide bandgap and deep valence‐band levels of blue quantum dots (QDs) hinder hole injection and induce severe charge imbalance, while operation at elevated luminance intensifies Joule heating, charge accumulation, multicarrier Auger recombination, and degradation of the emitting QDs and adjacent transport layers. These coupled thermal and electrical effects result in pronounced efficiency roll‐off and rapid lifetime deterioration. In this review, we examine the fundamental limitations of high‐luminance blue QLEDs and summarize recent strategies based on thermal management, charge balance enhancement, and leakage suppression. Furthermore, we discuss the remaining challenges in high‐luminance lifetime evaluation, efficiency retention, and device integration to provide perspectives for realizing bright and stable blue QLEDs in next‐generation displays.
