Real-time observation of nucleation and growth of Au on CdSe quantum dot templates

Giant Colloidal Quantum Dot/α-Ga2O3 Heterojunction for High Performance UV-Vis-IR Broadband Photodetector

Broadband optoelectronics, which extend from the UV to IR regions, are crucial for imaging, autonomous driving, and object recognition. In particular, photon detection efficiency relies significantly on semiconductor properties, such as absorption coefficients and electron-hole pair generation rate, which can be optimized by designing a suitable p-n junction. In this study, we devise giant PbS colloidal quantum dots (G-PbS CQDs) that exhibit high absorption coefficients and broadband absorption. To leverage these exceptional optical properties, we combine G-PbS CQDs with an ultrawide-bandgap semiconductor, α-Ga2O3, and create an efficient G-PbS CQD/α-Ga2O3 heterojunction photodetector that exhibits high performance across the UVC-vis-NIR spectrum range. The resultant heterojunction facilitates efficient electron-hole pair separation at the G-PbS CQD/α-Ga2O3 heterojunction. Furthermore, we utilize transparent graphene electrodes to overcome the limitations of conventional transistor-type device structures and the substantial optical losses induced by opaque metal electrodes. This strategy maximizes the light-collection area and results in an approximately 3-orders of magnitude higher responsivity (55.5 A/W) and specific detectivity (1.66 × 1013 Jones) compared to devices with opaque metal electrodes.

Probing Chemical-Composition-Induced Heterostructures and Interfaces in Lead Halide Perovskites

Lead halide perovskites (LHP) are of great interest for their optoelectronic properties and photovoltaic applications. Various heterostructures are created in these materials to achieve favorable optical properties and improved stability at the interfaces during the fabrication of devices. Such heterostructures are often assumed to be formed based on the reactivity of precursors and are not directly probed. In this Feature Article, we report how various strategies have been employed in LHP thin films and nanocrystals (NCs) that generate heterostructures to boost their stability and photovoltaic (PV) efficiencies and how variable energy photoelectron spectroscopy (VEPES) can probe the chemical composition variation in heterostructured materials and interfaces. We specifically discussed the internal heterostructures of LHP NCs generated due to the surface chemistry and postsynthesis anion exchange followed by a detailed discussion of the heterostructures induced by the chemical composition (anion, cation, and degradation) of LHP thin films. The difficulties in determining heterostructures as well as the potential scope of the application of VEPES in unwrapping heterostructures in diverse materials are also discussed.

State of the art of ultra-thin gold layers: formation fundamentals and applications

Fabrication of ultra-thin gold (Au) layers (UTGLs) has been regarded as the key technique to achieve applications with tunable optical response, flexible sensors and electronic devices. Various strategies have been developed to optimize the wetting process of Au, resulting in the formation of UTGLs at a minimum thickness. The related studies on UTGLs attracted huge attention in recent years. On the one hand, the growth processes of UTGLs on different substrates were in-depth probed by advanced in situ characterization techniques and the effects of optimization strategies on the growth of UTGLs were also revealed. On the other hand, based on the understanding of the growth behavior and the assistance of optimization strategies, various applications of UTGLs were realized based on optical/plasmon responses, surface-enhanced Raman scattering and as electrodes for various sensors and electronic devices, as well as being seed layers for thin film growth. In this focused review, both the fundamental and practical studies on UTGLs in the most recent years are elaborated in detail. The growth processes of UTGLs revealed by in situ characterization techniques, such as grazing-incidence small-angle X-ray scattering (GISAXS), as well as the state of the art of UTGL-based applications, are reviewed.