Explore the vast range of titles available.

The junctions formed at the contact between metallic electrodes and semiconductor materials are crucial components of electronic and optoelectronic devices 1 . Metal–semiconductor junctions are characterized by an energy barrier known as the Schottky barrier, whose height can, in the ideal case, be predicted by the Schottky–Mott rule 2 – 4 on the basis of the relative alignment of energy levels. Such ideal physics has rarely been experimentally realized, however, because of the inevitable chemical disorder and Fermi-level pinning at typical metal–semiconductor interfaces 2 , 5 – 12 . Here we report the creation of van der Waals metal–semiconductor junctions in which atomically flat metal thin films are laminated onto two-dimensional semiconductors without direct chemical bonding, creating an interface that is essentially free from chemical disorder and Fermi-level pinning. The Schottky barrier height, which approaches the Schottky–Mott limit, is dictated by the work function of the metal and is thus highly tunable. By transferring metal films (silver or platinum) with a work function that matches the conduction band or valence band edges of molybdenum sulfide, we achieve transistors with a two-terminal electron mobility at room temperature of 260 centimetres squared per volt per second and a hole mobility of 175 centimetres squared per volt per second. Furthermore, by using asymmetric contact pairs with different work functions, we demonstrate a silver/molybdenum sulfide/platinum photodiode with an open-circuit voltage of 1.02 volts. Our study not only experimentally validates the fundamental limit of ideal metal–semiconductor junctions but also defines a highly efficient and damage-free strategy for metal integration that could be used in high-performance electronics and optoelectronics. In metal–semiconductor junctions, interfacial bonding and disorder cause deviations from theoretical predictions for the energy barrier, but delicately transferring pre-fabricated metal films onto two-dimensional semiconductors can overcome this challenge.

Over the last few decades, research works have focused on elucidating the optical properties of semiconductor materials. Despite remarkable progress in the measurement and calculation of the absorption coefficient for semiconductor materials, there is a lack of comprehensive review on the comparative study of absorption coefficient properties for different types of bulk semiconductor materials and their methods for calculating the absorption coefficient. Hence, this paper summarizes the fundamentals of the various methods used to determine the absorption coefficient properties of bulk growth semiconductor crystals, and discusses their advantages and disadvantages. Furthermore, this review provides comprehensive results from recent studies and findings on the absorption properties of near- to mid-infrared (wavelengths from 800 to 7300 nm) group III-V semiconductor materials. In addition, the absorption coefficient of the conventional group IV semiconductors (silicon and Ge) were included for performance comparison. Critical analysis was done for the reviewed materials concerning their material properties, such as band gap structure, crystal quality, and the structural design of the device. The related studies on the methods to determine the absorption coefficients of semiconductors and to improve the likelihood of absorption performance were well highlighted. This review also provides an in-depth discussion on the knowledge of absorption coefficient based on a wide range of semiconductor materials and their potential for sensors, photodetectors, solar and photovoltaic application in the near to mid infrared region. Lastly, the future prospects for research on absorption coefficients are discussed and the advancement in the determination of absorption coefficients for new ternary and quaternary materials is proposed using artificial intelligence such as neural networks and genetic algorithm.

Recently, all-inorganic perovskite quantum dots (QDs) (CsPbX3, X = Cl, Br, I) as the emerging semiconductor materials have been intensively studied owing to superior optical properties. Currently, the strategy for preparation of inorganic perovskite QDs mainly focuses on the hot-injection method, but requires inert gas protection and is difficult to mass-produce. In this work, we developed a simple and low-cost strategy for preparing highly luminescent and air-stable all-inorganic perovskite QDs by directly heating perovskite precursors in octane in air. The emission wavelength of CsPbX3 perovskite QDs can be tunable from ultraviolet (UV) to infrared region by simply controlling their halide composition and display high PLQYs. Moreover, CsPbX3 perovskite QDs in octane can exist more than half a year in air and the film of CsPbX3 perovskite QDs also shows good thermal stability and air stability, especially high iodide-substituted CsPbBr3−xIx perovskite QDs. The CsPbX3 perovskite QDs can be easily blended with PDMS and used as color conversion layer on the blue LEDs chip for high-quality white LEDs. Our work opens a window for the potential application of such highly luminescent material in the fields of multicolor LEDs, backlight display and other related optoelectronic devices.

Graphitic carbon nitride (g-C 3 N 4 ) a polymeric semiconductor material is appealing research topic because of enhanced absorption capability in visible region. g-C 3 N 4 –TiO 2 composite material was prepared with varying composition (g-C 3 N 4 : TiO 2 ) in the range of 0.25:1–2:1 and studied using various characterization techniques including X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) and FTIR spectroscopy for structural and morphological analysis. Optical properties were studied using UV–Vis, and photoluminescence (PL) spectroscopic techniques and dielectric properties were studied using impedance analyser. UV–visible spectra show a shift toward the higher wavelength region in composite owing to the decrease in the band gap value of g-C 3 N 4 –TiO 2 composites. The dielectric constant was found increased with increasing content of g-C 3 N 4 till the composition of 1.5:1 and decreased for higher content. The optimum composition based on above studies was found to be 1:1 and 1.5:1 with optical absorption in the range of 280–420 nm covering UV and small portion of visible light, and recombination of photogenerated charge carriers were also reduced compared to g-C 3 N 4 .

This book presents both fundamental knowledge and latest achievements of this rapidly growing field in the last decade. It presents a complete and concise picture of the the state-of-the-art in the field, encompassing the most active international research groups in the world. Led by contributions from leading global research groups, the book discusses the functionalization of semiconductor surface. Dry organic reactions in vacuum and wet organic chemistry in solution are two major categories of strategies for functionalization that will be described. The growth of multilayer-molecular architectures on the formed organic monolayers will be documented. The immobilization of biomolecules such as DNA on organic layers chemically attached to semiconductor surfaces will be introduced. The patterning of complex structures of organic layers and metallic nanoclusters toward sensing techniques will be presented as well.

Polyanionic semiconductor materials are starting to receive widespread attention because of their relatively small band gap and size. Here, a class of (Mn, In) (S, Se) nanosheets with a porous structure is prepared by one-step solvothermal method. (Mn, In) (S, Se) nanosheets exhibit the most excellent photocatalytic hydrogen splitting performance (396 µmolg −1  h −1 ) under 300 w xenon lamp irradiation without sacrificial agent, which is 11 times higher than that of MnIn 2 Se 4 (35 µmolg −1  h −1 ). This work opens a new gateway to exploring polyanionic photocatalysts for photocatalytic applications. Graphical Abstract Herein, a novel polyanionic semiconductor photocatalyst (Mn, In) (S, Se) nanosheets with a porous structure were prepared for the first time by one-step solvothermal method. The synthesized porous nanosheets can be used for photocatalytic hydrogen production in pure water without sacrificial agents under the irradiation of a xenon lamp. The satisfactory performance of (Mn, In) (S, Se) is tightly connected with the layered porous structure, which leads to more exposed active sites and shorter migration distances of photogenerated electrons and holes. Moreover, this polyanion modification strategy makes the band gap of the material smaller and accelerates the electron migration rate.

For conventional dye or quantum dot sensitized solar cells, which are fabricated using mesoporous films, the inefficient electron transport due to defects such as grain boundaries and surface traps is a major drawback. To simultaneously increase the carrier transport efficiency as well as the surface area, optimal-assembling of hierarchical nanostructures is an attractive approach. Here, a three dimensional (3D) hierarchical heterostructure, consisting of CdS sensitized one dimensional (1D) ZnO nanorods deposited on two dimensional (2D) TiO 2 (001) nanosheet, is prepared via a solution-process method. Such heterstructure exhibits significantly enhanced photoelectric and photocatalytic H 2 evolution performance compared with CdS sensitized 1D ZnO nanorods/1D TiO 2 nanorods photoanode, as a result of the more efficient light harvesting over the entire visible light spectrum and the effective electron transport through a highly connected 3D network.

Two new types of novel difuran-coumarin discoid molecule substituted with long-chain alkyl groups were designed and synthesized, which furan-group was successfully coupled with coumarin as the starting material. In this paper, the synthesis method of the peripheral halogenation of novel difuran-coumarin discoid molecules was studied, and its solubility was improved through modification of its periphery, which makes them have high solution processability. And it can expectedly be used as one candidate of organic semiconductor materials.

Organic polymer semiconductor materials are conveniently tuned to energy levels because of their good chemically modifiable properties, thus enhancing their carrier transport capabilities. Here, we have designed and prepared a polymer with a donor-acceptor structure and tested its potential as a p-type material for organic field-effect transistor (OFET) applications using a solution-processing method. The conjugated polymers, obtained via the polymerization of the two monomers relying on the Stille coupling reaction, possess extremely high molecular weights and thermodynamic stability. Theoretical-based calculations show that PDPP-2S-Se has superior planarity, which is favorable for carrier transport within the main chain. Photophysical and electrochemical measurements systematically investigated the properties of the material and the energy levels with respect to the theoretical values. The maximum hole mobility of the PDPP-2S-Se-based OFET device is 0.59 cm2 V−1 s−1, which makes it a useful material for potential organic electronics applications.

Organic polymer semiconductor materials, due to their good chemical modifiability, can be easily tuned by rational molecular structure design to modulate their material properties, which, in turn, affects the device performance. Here, we designed and synthesized a series of materials based on terpolymer structures and applied them to organic thin-film transistor (OTFT) device applications. The four polymers, obtained by polymerization of three monomers relying on the Stille coupling reaction, shared comparable molecular weights, with the main structural difference being the ratio of the thiazole component to the fluorinated thiophene (Tz/FS). The conjugated polymers exhibited similar energy levels and thermal stability; however, their photochemical and crystalline properties were distinctly different, leading to significantly varied mobility behavior. Materials with a Tz/FS ratio of 50:50 showed the highest electron mobility, up to 0.69 cm2 V−1 s−1. Our investigation reveals the fundamental relationship between the structure and properties of materials and provides a basis for the design of semiconductor materials with higher carrier mobility.