The presence of localized trap states on the surface of CsPbCl 3 perovskite nanocrystals (NCs) is one of the greatest challenges precluding the development of optoelectronic applications of these NCs. Passivation of these defect sites provides a promising pathway to remediating their electronic and optical properties, such as the photoluminescence quantum yield (PLQY). Herein, we demonstrate a postsynthetic dual-surface treatment using trivalent metal ion salts, i.e., YCl 3 , as a new passivation approach that enhances the PLQY up to 60% while preserving the NC size and crystal structure. Such remarkable enhancement of the PLQY along with prolongation of the average PL lifetimes of treated NCs samples indicates effective passivation of the surface defects and subsequent suppression of the formation of surface nonradiative recombination centers. As a segue toward optoelectronic applications, we probed the photoelectric performance of the NCs using ultraflexible devices; we found that YCl 3 -treated CsPbCl 3 NC films exhibit an order of magnitude larger photocurrent compared to their nontreated counterparts. Our experimental and theoretical results provide an insightful understanding of the effective passivating roles of Y 3+ and Cl − ions on the surface of CsPbCl 3 NCs, as well as offering a new path to synthesize high-quality NCs for UV light conversion applications.

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MXenes have recently shown impressive optical and plasmonic properties associated with their ultrathin‐atomic‐layer structure. However, their potential use in photonic and plasmonic devices has been only marginally explored. Photodetectors made of five different MXenes are fabricated, among which molybdenum carbide MXene (Mo2CTx) exhibits the best performance. Mo2CTx MXene thin films deposited on paper substrates exhibit broad photoresponse in the range of 400–800 nm with high responsivity (up to 9 A W−1), detectivity (≈5 × 1011 Jones), and reliable photoswitching characteristics at a wavelength of 660 nm. Spatially resolved electron energy‐loss spectroscopy and ultrafast femtosecond transient absorption spectroscopy of the MXene nanosheets reveal that the photoresponse of Mo2CTx is strongly dependent on its surface plasmon‐assisted hot carriers. Additionally, Mo2CTx thin‐film devices are shown to be relatively stable under ambient conditions, continuous illumination and mechanical stresses, illustrating their durable photodetection operation in the visible spectral range. Micro‐Raman spectroscopy conducted on bare Mo2CTx film and on gold electrodes allowing for surface‐enhanced Raman scattering demonstrates surface chemistry and a specific low‐frequency band that is related to the vibrational modes of the single nanosheets. The specific ability to detect and excite individual surface plasmon modes provides a viable platform for various MXene‐based optoelectronic applications.

The photocurrent conversions of transition metal dichalcogenide nanosheets are unprecedentedly impressive, making them great candidates for visible range photodetectors. Here we demonstrate a method for fabricating micron-thick, flexible films consisting of a variety of highly separated transition metal dichalcogenide nanosheets for excellent band-selective photodetection. Our method is based on the non-destructive modification of transition metal dichalcogenide sheets with amine-terminated polymers. The universal interaction between amine and transition metal resulted in scalable, stable and high concentration dispersions of a single to a few layers of numerous transition metal dichalcogenides. Our MoSe2 and MoS2 composites are highly photoconductive even at bending radii as low as 200 μm on illumination of near infrared and visible light, respectively. More interestingly, simple solution mixing of MoSe2 and MoS2 gives rise to blended composite films in which the photodetection properties were controllable. The MoS2/MoSe2 (5:5) film showed broad range photodetection suitable for both visible and near infrared spectra.

as hybridization of MoS 2 with quantum dots and heterostructures with other 2D materials to suppress the dark current and enhance the broad spectral range in the NIR region were attempted. While convenient, these approaches are not scalable for large-scale implementation due to the complicated procedures as well as expensive material and instrument-related costs. [17][18][19] To overcome the aforementioned issues, a promising approach is to create multifunctional hybrid photodetectors by simple solution mixing of MoS 2 with other 2D materials. The different band gaps and dark currents of 2D materials and the low-cost solution process offers a convenient route to engineering and controlling the photodetection properties. [20][21][22] In addition, the arrays of hybrid photodetectors fabricated on flexible substrates, such as plastic and paper, would be beneficial for future wearable applications. [23,24] Recently, 2D organic semiconductors, such as graphitic carbon nitride (g-C 3 N 4 ), have emerged as promising UV-and visible-light-active photocatalysts in the arena of solar energy conversion and environmental applications. [25][26][27][28] Their unique electrical and optical properties, wide band gap (≈2.7 eV), stability in ambient conditions, and low dark current make them attractive for UV light photodetection, but very little work has been carried out so far. Compared to other 2D materials, by considering its merits, g-C 3 N 4 is a promising candidate for hybridizing with MoS 2 because not only does it suppress the dark current of MoS 2 , but also allows hybrid broadband photodetection from UV to visible region. In addition, the crystal lattice matching [29,30] and the ultrafast charge transfer between MoS 2 and g-C 3 N 4 at the interface may lead to efficient separation of photogenerated carriers, as predicted by a recent computational study. [31] Herein we report, to the best of our knowledge for the first time, mechanically flexible 2D organic-inorganic hybrid thin film photodetectors consisting of inorganic MoS 2 and organic g-C 3 N 4 nanosheets for broadband photodetection. Simple but robust solution mixing of MoS 2 and g-C 3 N 4 offers an extremely convenient route to controlling their composition in the hybrid films and thus allows for tuning the optoelectronic properties. Hybrid thin films with 5:5 ratio of MoS 2 and g-C 3 N 4 (henceforth denoted as 5:5 hybrid films) exhibited excellent photodetection performance in terms of ON/OFF photocurrent ratio, specific detectivity, responsivity, and response time upon both Flexible 2D inorganic MoS 2 and organic g-C 3 N 4 hybrid thin film photodetectors with tunable composition and photodetection properties are developed using simple solution processing. The hybrid films fabricated on paper substrate show broadband photodetection suitable for both UV and visible light with good responsivity, detectivity, and reliable and rapid photoswitching characteristics comparable to monolayer devices. This excellent performance is retained even after the films are severely...