Search

Stacking single layers of atoms on top of each other provides a fundamental way to achieve novel material systems and engineer their physical properties, which offers opportunities for exploring fundamental physics and realizing next-generation optoelectronic devices. Among the two-dimensional (2D)-stacked systems, transition metal dichalcogenide (TMDC) heterostructures are particularly attractive because they host tightly-bonded interlayer excitons which possess various novel and appealing properties. These interlayer excitons have drawn significant research attention and hold high potential for the application in unique optoelectronic devices, such as polarization- and wavelength-tunable single photon emitters, valley Hall transistors, and possible high-temperature superconductors. The development of these devices requires a comprehensive understanding of the fundamental properties of these interlayer excitons and the impact of electric fields on their behaviors. In this review, we summarize the recent advances on the understanding of interlayer exciton dynamics under electric fields in TMDC heterostructures. We put emphasis on the electrical modulation of interlayer excitons' emission, the valley Hall transport of charge carriers after the separation of interlayer excitons by an electric field, and the correlation physics of interlayer excitons and charges under electrical doping and tuning. Challenges and perspectives are finally discussed for the application of TMDC heterostructures in future optoelectronics. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been investigated recently in perovskite photovoltaics owing to their potential to boost optoelectronic performance and device stability. However, the impact of variations in the MOF side chain on perovskite characteristics and the mechanism of MOF/perovskite film formation remains unclear. In this study, three nanoscale thiol‐functionalized UiO‐66‐type Zr‐based MOFs (UiO‐66‐(SH)2, UiO‐66‐MSA, and UiO‐66‐DMSA) are systematically employed and examined in perovskite solar cells (PSCs). Among these MOFs, UiO‐66‐(SH)2, with its rigid organic ligands, exhibited a strong interaction with perovskite materials with more efficient suppression of perovskite vacancy defects. More importantly, A detailed and in‐depth discussion is provided on the formation mechanism of UiO‐66‐(SH)2‐assisted perovskite film upon in situ GIWAXS performed during the annealing process. The incorporation of UiO‐66‐(SH)2 additives substantially facilitates the conversion of PbI2 into the perovskite phase, prolongs the duration of stage I, and induces a delayed phase transformation pathway. Consequently, the UiO‐66‐(SH)2‐assisted device demonstrates reduced defect density and superior optoelectronic properties with optimized power conversion efficiency of 24.09% and enhanced long‐term stability under ambient environment and continuous light illumination conditions. This study acts as a helpful design guide for desired MOF/perovskite structures, enabling further advancements in MOF/perovskite optoelectronic devices. [ABSTRACT FROM AUTHOR]

Metal halide perovskites can be readily synthesized, they exhibit tunable physical properties and excellent performance, and they are heavily studied optoelectronic materials. Compared to the typical three-dimensional perovskites, morphological-level one-dimensional (1D) nanostructures enable charge transport and photon propagation with low exciton binding energies and long charge-carrier diffusion lengths, while molecular-level 1D nanostructures exhibit good compositional and structural flexibilities, highly tunable bandgaps, strong quantum confinement effects, and excellent ambient stabilities. The 1D natures of these emerging halide perovskites enhance the performance of optoelectronic devices. Herein, we highlight recent progress realized in the syntheses and characterizations of both morphological- and molecular-level 1D halide perovskites with tunable structures, compositions, and properties, as well as their photovoltaic, light-emission, and photodetection applications. In addition, current challenges, future prospects, and promising research directions are discussed to provide guidance in advancing the field of 1D perovskites. The recent advances realized in the syntheses and characterizations of both morphological- and molecular-level one-dimensional (1D) metal-halide perovskites with tunable structures, compositions, and properties, as well as optoelectronic applications are comprehensively reviewed. Furthermore, the challenges, prospects, and promising research directions are discussed, which we believe will help to accelerate the explorations of 1D metal-halide perovskites in the future. [ABSTRACT FROM AUTHOR]

Being a representative candidate from the two-dimensional (2D) materials family, graphene has been one of the most intensively researched candidates because of its ultrahigh carrier mobility, quantum Hall effects, excellent mechanical property and high optical transmittance. Unfortunately, the lack of a band gap makes graphene a poor fit for digital electronics, where the current on/off ratio is critical. Huge efforts have been advocated to discover new 2D layered materials with wonderful properties, which complements the needs of 2D electronics. Appropriately designed graphene based hybrid structure could perform better than its counterpart alone. The graphene hybrid structure soon become one of the most exciting frontiers in advanced 2D materials, and many efforts have been made to create artificial heterostructures by assembling of graphene with various layered materials. In this review, we present the recent development in synthesis and applications of graphene based 2D heterostructures. Although 2D transition metal dichalcogenide semiconductors have been demonstrated as strong candidates for next-generation electronics and optoelectronics, by combining advantages of various properties of 2D materials together with graphene, it is highly possible to build entire digital circuits using atomically thin components, and create many novel devices that can be utilized in different areas. [ABSTRACT FROM AUTHOR]

In recent years there have been many breakthroughs in two-dimensional (2D) nanomaterials, among which the transition metal dichalcogenides (TMDs) attract significant attention owing to their unusual properties associated with their strictly defined dimensionalities. TMD materials with a generalized formula of MX2, where M is a transition metal and X is a chalcogen, represent a diverse and largely untapped source of 2D systems. Semiconducting TMD monolayers such as MoS2, MoSe2, WSe2 and WS2 have been demonstrated to be feasible for future electronics and optoelectronics. The exotic electronic properties and high specific surface areas of 2D TMDs offer unlimited potential in various fields including sensing, catalysis, and energy storage applications. Very recently, the chemical vapour deposition technique (CVD) has shown great promise to generate high-quality TMD layers with a scalable size, controllable thickness and excellent electronic properties. Wafer-scale deposition of mono to few layer TMD films has been obtained. Despite the initial success in the CVD synthesis of TMDs, substantial research studies on extending the methodology open up a new way for substitution doping, formation of monolayer alloys and producing TMD stacking structures or superlattices. In this tutorial review, we will introduce the latest development of the synthesis of monolayer TMDs by CVD approaches. [ABSTRACT FROM AUTHOR]

We prepared high-performance photoresistors based on CH3NH3PbI3 films with a high PbI2 doping level. The role of PbI2 in CH3NH3PbI3 perovskite thin film was systematically investigated using scanning electron microscopy, X-ray diffraction, time-resolved photoluminescence spectroscopy, and photoconductive atomic force microscope. Laterally-structured photodetectors have been fabricated based on CH3NH3PbI3 perovskite thin films deposited using precursor solution with various CH3NH3I:PbI2 ratios. Remarkably, the introduction of a suitable amount of PbI2 can significantly improve the performance and stability of perovskite-based photoresistors, optoelectronic devices with ultrahigh photo-sensitivity, high current on/off ratio, fast photo response speed, and retarded decay. Specifically, a highest responsivity of 7.8 A/W and a specific detectivity of 2.1 × 1013 Jones with a rise time of 0.86 ms and a decay time of 1.5 ms have been achieved. In addition, the local dependence of photocurrent generation in perovskite thin films was revealed by photoconductive atomic force microscopy, which provides direct evidence that the presence of PbI2 can effectively passivate the grain boundaries of CH3NH3PbI3 and assist the photocurrent transport more effectively. [ABSTRACT FROM AUTHOR]

Abstract: A new rare-earth complex TbY(p-MBA)6(phen)2 was synthesized and studied. Pure green emission was observed from the devices that were fabricated with the structure as follows: Device 1: ITO/PVK: TbY(p-MBA)6(phen)2/LiF/Al; Device 2: ITO/PVK: TbY(p-MBA)6(phen)2/AlQ/LiF/Al. PVK was used to improve the film-forming and hole-transporting properties of the TbY(p-MBA)6(phen)2. The characteristics of these devices were investigated and compared with Tb(p-MBA)3phen, which had been reported. The results show that TbY(p-MBA)6(phen)2 has much better performance than Tb(p-MBA)3phen. This improvement is attributed to the introduction of yttrium. The highest EL brightness of Device 1 is 37.5cd/cm2 at a fixed bias of 19V, and the highest EL brightness of Device 2 reaches 333.7cd/cm2 at 23V. [Copyright &y& Elsevier]

Monolayer molybdenum disulfide (MoS2) is a two-dimensionaldirect band gap semiconductor with unique mechanical, electronic,optical, and chemical properties that can be utilized for novel nanoelectronicsand optoelectronics devices. The performance of these devices stronglydepends on the quality and defect morphology of the MoS2layers. Here we provide a systematic study of intrinsic structuraldefects in chemical vapor phase grown monolayer MoS2, includingpoint defects, dislocations, grain boundaries, and edges, via directatomic resolution imaging, and explore their energy landscape andelectronic properties using first-principles calculations. A richvariety of point defects and dislocation cores, distinct from thosepresent in graphene, were observed in MoS2. We discoverthat one-dimensional metallic wires can be created via two differenttypes of 60° grain boundaries consisting of distinct 4-fold ringchains. A new type of edge reconstruction, representing a transitionstate during growth, was also identified, providing insights intothe material growth mechanism. The atomic scale study of structuraldefects presented here brings new opportunities to tailor the propertiesof MoS2via controlled synthesis and defect engineering. [ABSTRACT FROM AUTHOR]

Abstract: In this letter, we have fabricated an efficient, color stable white organic electroluminescent device through the incorporation of double thin 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) emitting layers and 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), a hole transporting and blue emitting material. The device structure is ITO/NPB 45nm/DCJTB 0.15nm/NPB 5nm/DCJTB 0.15nm/BCP 10nm/AlQ 50nm/LiF 0.3nm/Al 150nm. This device exhibited a pure white-light emission having Commission Internationale de I’Eclairage (CIE) coordinates of (0.324, 0.336), a current efficiency of 2.9cd/A and a maximum brightness of 7016cd/m2. When the current density increased from 2mA/cm2 to 100mA/cm2, we observed only a slight shifting in the CIE coordinates from (0.324, 0.336) to (0.320, 0.326). Moreover, the efficiency of the device with double thin emitting layers of DCJTB is two times higher than the device with only one DCJTB layer. [Copyright &y& Elsevier]