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Interface in perovskite solar cells (PSCs) is of vital importance because it dominates deep‐level defects and non‐radiative recombination, thus impacting both efficiency and stability further. Herein, a symmetrical acceptor–donor–acceptor (A–D–A) conjugated molecule with the core architecture of terthieno[3,2‐b hiophene and 2‐(3‐oxo‐2,3‐dihydro‐1 H‐inden‐1‐ylidene)malononitrile, named 6TIC, as a versatile buffer layer, is adopted to enhance photovoltaic performance and stability simultaneously. It is found that the conjugated molecule filling at grain boundaries and surface can not only chemically anchor with perovskite components to substantially eliminate interfacial defects and suppress detestable non‐radiative recombination, but also effectively improve the energy level alignment and facilitate charge transfer efficiency at the interface, resulting in an excellent power conversion efficiency of 24.81% with an admirable fill factor of 84.5%. Furthermore, benefiting from the unexceptionable surface protection effect of the hydrophobic buffer layer, greatly improved operational stability is delivered, with retaining 90% of initial efficiency for 960 h aging in a relative humidity of 60 ± 5% air and 1450 h aging under continuous 85 °C heating stress. This strategy may provide a new avenue for advancing high‐efficiency and stable PSCs. [ABSTRACT FROM AUTHOR]

Despite the swift development in perovskite solar cells (PSCs), great concerns regarding environmental vulnerability propose a big challenge for their long‐term operational stability. Herein, a novel functionalized ultraviolet (UV) conversion small molecule, Coumarin 153 (C153), is judiciously introduced into perovskite precursor to effectively enhance device efficiency and operational stability against UV radiation. It is found that the uncoordinated Pb2+ and A‐site vacancies of perovskite can be successfully fixed through Lewis acid–base coordination and hydrogen bonding upon C153 treatment, resulting in a stabilized structure with remarkably reduced intrinsic defects. Concurrently, the incremental visible light absorption derived from the down‐conversion effect of C153 molecules together with the optimized energy level arrangement contribute to the substantially enhanced photocurrent of the device. As a result, the resultant device delivers a champion efficiency of 24.73%, accompanied by greatly improved operational stability against environments, with retaining over 90% of initial PCE for ≈380, ≈1400, and 1710 h aging under continuous UV radiation, heating stress, and illumination, respectively. This work provides an effective and feasible strategy toward high‐efficiency and environment‐stable PSCs. [ABSTRACT FROM AUTHOR]

In this paper, the optical fiber ammonia sensor based on porous Yb3+/Er3+ co-doped NaYF4 up-conversion material/phenol red composites and optical fiber with end plane fusion sphere was proposed. Phenol red and Yb3+/Er3+ co-doped NaYF4 were mixed thoroughly and fixed stably in the polyvinylidene fluoride (PVDF) matrix. The optical fiber with end plane fusion sphere was inserted into the sensitive composite material to form ammonia sensitive probe. The ammonia concentration will affect the intensity of absorption of up-conversion luminescence located at 545 nm by phenol red because of the reaction between ammonia and phenol red. The detected intensity of up-conversion luminescence near 545 nm decreases with the increasing ammonia concentration. The signal wavelength will not be affected by the background visible light due to the 980 nm wavelength of excitation is far from the signal wavelength. The response time and recover time also were measured and discussed. [ABSTRACT FROM AUTHOR]

Fundamental understanding of charge behavior inside heterostructures is of vital importance for advancing high-performance optoelectronic applications. However, the charge behavior of 0D-2D mixed-dimensional van der Waals heterostructures (MvdWHs) in the photoexcited state remains elusive. In this work, an energy band alignment protocol is adopted to realize effective energy band structure engineering inside 0D-2D MvdWHs of perovskite quantum dots and MoS2 monolayer with precisely designed typical type I and type II heterostructures, respectively. A profile and in-depth understanding of interfacial photoinduced charge behavior is determined from two opposite perspectives based on MvdWHs. Sufficient comparison of a series of optical characterization results, including Raman shift, quenched photoluminescence, visualized suppressed fluorescence intensity, and shortened fluorescence lifetime imaging, clearly verifies that interfacial charge behavior can be tailored by varying the band alignment in 0D-2D MvdWHs. Furthermore, the photoresponse performance and the relatively stronger and weaker photogating effects of such MvdWH-based phototransistors also demonstrate modulation of interfacial charge behavior in 0D-2D MvdWHs via energy band structure engineering, which is still feasible for optoelectronic performance optimization. These results are expected to shed light on designing novel functional devices and advancing the development process of 0D-2D MvdWHs in the foreseeable future. [ABSTRACT FROM AUTHOR]

Abstract: Here, the effect of E‐beam irradiation on the transport properties of the monolayer MoS2 is investigated in situ using scanning electron microscope (SEM). The results show that the source drain current is increased under E‐beam irradiation; the current gradually increases to a saturation value with an increase in irradiation time, and the saturation value increases with an increase in E‐beam intensity. After E‐beam irradiation, X‐ray photoelectron spectroscopy (XPS) results show that the stoichiometry of MoS2 is modified, while the Raman and PL results reveal that the optical performance of the monolayer MoS2 is not deteriorated. The source–drain current and electron mobility of the MoS2 transistor are reduced by E‐beam irradiation, while the on–off current ratio of the transistor almost unchanges. However, the photoresponse performance, such as the light dark current ratio, response, and release speed of the device are improved. The results are discussed by the creation of defects which vary the injected and trapped charges of the sample by E‐beam irradiation. The results provide a new method to improve the optoelectronic performance of two dimensional (2D) materials devices. [ABSTRACT FROM AUTHOR]

Abstract: Here, it is first reported that a self‐powered photodetector based on a MoS2/CH3NH3PbI3 vertical type heterojunction, which has responsivity of 60 mAW−1 and response/recovery time of 2149/899 ms. Under bias, it exhibits a photoswitching ratio exceeding 1522, fast response/recovery time of 205/206 ms, and high photoresponsivity of 68.11 AW−1. The optoelectronic performances of the photodetector are closely related to the type of the MoS2/CH3NH3PbI3 heterojunction, which acts as a hole (electron) transport field and can effectively decrease the recombination of holes and electrons. Additionally, the MoS2/CH3NH3PbI3 planar type heterojunction is also built to compare with the vertical type in optoelectronics behavior. Due to the existence of internal field, the properties of vertical type photodetector are better than those of the planar type which also presents good performance with on/off ratio up to 1476, photoresponsivity of 28 AW−1, and response rate of 356/204 ms. These results pave a new way to form an ultrahigh performance MoS2/CH3NH3PbI3 heterojunction, hold the promise for construction of a self‐powered photodetector, and develop promising atomically thin MoS2 heterostructure device for photovoltaic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Combining intriguing physical properties of 2D crystals and intrinsically remarkable optical properties of halide perovskite quantum dots (QDs), the 0D–2D perovskite QD–based mixed dimensional van der Waals heterostructure (MvdWH) is considered as promising for optoelectronic applications. Even though the interfacial electronic structure of MvdWHs is sufficiently engineered to manipulate the charge carrier behavior, the issue of interfacial charge transfer efficiency originating from the residue ligands that are inevitably introduced by the QDs is still prominently remained. From this perspective, for the first time, a solution‐processed surface ligand density control strategy is demonstrated to balance the QD surface passivation and the interfacial charge carrier extraction and injection efficiency in the 0D–2D MvdWH system. The accurate adjustment of ligand density outside QDs enables the subsequent modulation on interfacial charge carrier transfer efficiency from the aspect of electronic and optoelectronic properties. Furthermore, such kind of ligand engineering toward MvdWH interface is substantially demonstrated in a photogating mechanism–based phototransistor with an improved photoresponsivity as high as 1.13 × 105 A W−1. These results may push forward the evolution of 0D–2D mixed dimensional van der Waals optoelectronics. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenide (2D‐TMD) materials and their van der Waals heterostructures (vdWHs) have inspired worldwide efforts in the fields of electronics and optoelectronics. However, photodetectors based on 2D/2D vdWHs suffer from performance limitations due to the weak optical absorption of their atomically thin nature. In this work, taking advantage of an excellent light absorption coefficient, low‐temperature solution‐processability, and long charge carrier diffusion length, all‐inorganic halides perovskite CsPbI3−xBrx quantum dots are integrated with monolayer MoS2 for high‐performance and low‐cost photodetectors. A favorable energy band alignment facilitating interfacial photocarrier separation and efficient carrier injection into the MoS2 layer inside the 0D–2D mixed‐dimensional vdWHs are confirmed by a series of optical characterizations. Owing to the synergistic effect of the photogating mechanism and the modulation of Schottky barriers, the corresponding phototransistor exhibits a high photoresponsivity of 7.7 × 104 A W−1, a specific detectivity of ≈5.6 × 1011 Jones, and an external quantum efficiency exceeding 107%. The demonstration of such 0D–2D mixed‐dimensional heterostructures proposed here would open up a wide realm of opportunities for designing low‐cost, flexible transparent, and high‐performance optoelectronics. All‐inorganic perovskite quantum dots are integrated with monolayer MoS2 for a high‐performance and low‐cost photodetector. Owing to the synergistic effect of the photogating mechanism and Schottky barriers modulation, this type‐II band alignment 0D–2D mixed‐dimensional van der Waals heterostructured phototransistor exhibits a high photoresponsivity of 7.7 × 104 A W−1, a specific detectivity of ≈5.6 × 1011 Jones, and an external quantum efficiency exceeding 107%. [ABSTRACT FROM AUTHOR]