This review article focuses on the sol-gel preparation of high temperature superconducting oxides wherein different classes of gel technologies were utilized. These involve: 1) the sol-gel route based upon hydrolysis-condensation of metal-alkoxides, 2) the gelation route based upon concentration of aqueous solutions involving metal-chelates, often called as “chelate gel” or “amorphous chelate” route, and 3) the organic polymeric gel route. This paper reviews the current status of these sol-gel processes, and illustrates the underlying chemistry involved in each sol-gel technology. It is demonstrated that the chemical homogeneity of the gel is often disturbed by the differences in the chemistries of the cations. Prior to gelation the starting precursor solution containing various forms of metal-complexes must be chemically modified to overcome this problem. Illustration of a variety of strategies for success in obtaining a homogeneous multicomponent gel with no precipitation is focal point of this review article.

Invited review “sol-gel” preparation of high temperature superconducting oxides

We demonstrate extraordinary photoconductive behavior in two-dimensional (2D) crystalline indium selenide (In2Se3) nanosheets. Photocurrent measurements reveal that semiconducting In2Se3 nanosheets have an extremely high response to visible light, exhibiting a photoresponsivity of 3.95 × 102 A·W–1 at 300 nm with an external quantum efficiency greater than 1.63 × 105 % at 5 V bias. The key figures-of-merit exceed that of graphene and other 2D material-based photodetectors reported to date. In addition, the photodetector has a fast response time of 1.8 × 10–2 s and a specific detectivity of 2.26 × 1012 Jones. The photoconductive response of α-In2Se3 nanosheets extends into ultraviolet, visible, and near-infrared spectral regions. The high photocurrent response is attributed to the direct band gap (EG = 1.3 eV) of In2Se3 combined with a large surface-area-to-volume ratio and a self-terminated/native-oxide-free surface, which help to reduce carrier recombination while keeping fast response, allowing for real-...

Extraordinary photoresponse in two-dimensional In(2)Se(3) nanosheets.

Properties of gallium selenide single crystal

Orthorhombic Bi2S3 (bismuthinite) nanorods and nanowires are synthesized by the solventless thermolysis of bismuth alkylthiolate precursors. Reactions carried out in air at ∼225 °C in the presence of a capping ligand species, octanoate, produce high aspect ratio (>100) nanowires. Lower aspect ratio nanowires (∼7) are produced by the same approach with the addition of elemental sulfur at lower reaction temperature (∼160 °C). Both the nanowires and nanorods are oriented with their long axes in the [002] crystallographic direction. Higher reaction temperatures (∼250 °C) produce crossed nanowire networks, or fabrics, with highly oriented growth as a result of heterogeneous nanowire nucleation and epitaxial elongation off the surface of existing wires.

Solventless Synthesis of Bi2S3 (Bismuthinite) Nanorods, Nanowires, and Nanofabric

Transport and phototransport properties of crystalline indium monoselenide (InSe) doped with a variety of elements are reported. Measured mobilities, lifetimes, and effective diffusion lengths of photoexcited carriers are used to interpret electrical and photovoltaic properties of several different structures. These include p‐n junctions, bismuth/p‐type InSe, platinum/n‐type InSe, and indium tin oxyde (ITO)/p‐type InSe. External solar efficiencies of the best devices are between 5% and 6%. The influence on the efficiency of the various parameters is evaluated, and ways of improvement are discussed.

/pdf/photoconductivity-and-photovoltaic-effect-in-indium-selenide-3qto981sby.pdf

Photoconductivity and photovoltaic effect in indium selenide

Photovoltaic efficiency of InSe solar cells

The transport properties of indium monoselenide have been measured in n- and p-type material. Parameters for photoexcited carriers are given. Fabrication procedures for Schottky and p-n diodes are reported. Photovoltaic spectra are fitted with measured values of transport and optical parameters. InSe is shown to be a new material with attractive characteristics for solar energy conversion. Performance of InSe solar cells is discussed.

https://hal.archives-ouvertes.fr/jpa-00244584/document

Photovoltaic effect in InSe - Application to Solar Energy Conversion

Impurity levels and electron scattering mechanisms in bismuth sulfide have been investigated by means of resistivity and Hall-effect measurements in the 30--500-K temperature range. Lattice scattering is predominant in this range and the temperature dependence of the electron mobility, in the crystallographic directions a and c, has been quantitatively interpreted through Fivaz-Schmid and Brooks-Herring models for homopolar optical phonon and ionized impurities scattering, respectively, yielding the energy of the phonon mode (\ensuremath{\Elzxh}\ensuremath{\omega}=14 meV) and the electron-phonon coupling constant (${g}^{2}$\ensuremath{\gtrsim}0.4). The density-of-states effective mass in the conduction band has also been determined from Seebeck-effect measurements at room temperature.

Transport properties of bismuth sulfide single crystals.

Photovoltaic and photoelectronic properties of GaSe and InSe metal-semiconductor contacts are reported. The shape of the spectra, at room temperature, can be interpreted with reasonable values for diffusion length and junction depth. The variation of the spectra with pressure in GaSe and the shape of the low-energy tail in InSe are in concordance with the indirect nature of the lower energy gaps in both compounds. A comparison of these materials with other semiconductors for photovoltaic conversion purposes is given.

Photovoltaic properties of GaSe and InSe junctions

Hall effect and resistivity measurements in silicon doped indium selenide (InSe), from 7K to 500K, are reported. Results are interpreted through a model, previously proposed for tin doped InSe, that takes into account the contribution of both three- and two-dimensional electrons to charge transport along the layers in InSe.

A. Segura

Papers

Photovoltaic efficiency of InSe solar cells

Photovoltaic effect in InSe - Application to Solar Energy Conversion

Transport properties of bismuth sulfide single crystals.

Photovoltaic properties of GaSe and InSe junctions

Transport properties of silicon doped n-indium selenide