Rich Chemistry in Inorganic Halide Perovskite Nanostructures.

Halide perovskites have emerged as a class of promising semiconductor materials owing to their remarkable optoelectronic properties exhibiting in solar cells, light-emitting diodes, semiconductor lasers, etc. Inorganic halide perovskites are attracting increasing attention because of the higher stability toward moisture, light, and heat as compared with their organic-inorganic hybrid counterparts. In particular, inorganic halide perovskite nanomaterials provide controllable morphology, tunable optoelectronic properties, and improved quantum efficiency. Here, the development controlled synthesis of desired inorganic halide perovskite nanostructures by various chemical approaches is described. Utilizing these nanostructures as platforms, anion exchange chemistry for wide compositional and optical tunabilities is described, and the rich structural phase transition phenomenon and mechanism investigated systematically. Furthermore, these nanostructures and extracted knowledge are applied to design photonic, photovoltaic, and thermoelectric devices. Finally, future directions and challenges toward improvement of the optical, electrical, and optoelectronic properties, exploration of the anion and cation exchange kinetics, and alleviation of the stability and toxicity issues in inorganic lead based halide perovskites are discussed to provide an outlook on this promising field

High-performance near-infrared photodetector based on nano-layered MoSe2

In recent years, the integration of two-dimensional (2D) nanomaterials, especially transition metal chalcogendies (TMCs) and dichalcogendies (TMDCs), into electronic devices have been extensively studied owing to their exceptional physical properties such as high transparency, strong photoluminescence, and tunable bandgap depending on the number of layers. Herein, we report the optoelectronic properties of few-layered MoSe2-based backgated phototransistor used for photodetection. The photoresponsivity could be easily controlled to reach a maximum value of 238 AW–1 under near-infrared light excitation, achieving a high specific detectivity D∗ = 7.6×10** cmHz*/1W3* . Few-layered MoSe2 exhibited excellent optoelectronic properties as compared with those reported previously for multilayered 2D material-based photodetectors, indicating that our device is one of the best high-performance nanoscale near-infrared photodetector based multilayered two-dimensional materials

Synthesis and optoelectronic properties of new ethynylated pyrazine derivatives

Several diaryleneethynylpyrazine derivatives, in which the pyrazine unit is electron-deficient, have been synthesised using Sonogashira palladium-catalysed cross-coupling reactions. Compound 32, an important intermediate in the synthesis of diaryleneethynylpyrazine derivatives was made by a modified literature procedure which improved the yield. Examination of optical absorption and photoluminescence spectra of compound 37 shows that the pyrazine unit does not change the behaviour significantly compared to analogue 42, while compound 38 shows pyridine substituents have a profound effect on the photophysics of these pyrazine systems. The redox properties of representative compound 37 were studied by cyclic voltammetry, which shows that reduction of 37 to its radical anion occurs as a reversible process at high negative potentials of ca. -1.87 V. The X-ray crystal structure of 37 is also presented. Quantum mechanical calculations of the geometry and electronic structure were performed for compound 37; the known phenylene analogue 42 was calculated at the same level for comparison. The results show that the energies of both HOMO and LUMO orbitals of 37 are decreased compared to 42. The calculated value of the HOMO-LUMO gap of 37 (3.56 eV) is close to that estimated from the red edge of the longest wavelength absorption (382 nm = 3.25 eV)

Orbital-Energy Splitting in Anion Ordered Ruddlesden-Popper Halide Perovskites for Tunable Optoelectronic Applications

The electronic orbital characteristics at the band edges plays an important role in determining the electrical, optical and defect properties of perovskite photovoltaic materials. It is highly desirable to establish the relationship between the underlying atomic orbitals and the optoelectronic properties as a guide to maximize the photovoltaic performance. Here, using first-principles calculations and taking anion ordered Ruddlesden-Popper (RP) phase halide perovskites Cs$_{n+1}$Ge$_n$I$_{n+1}$Cl$_{2n}$ as an example, we demonstrate how to rationally optimize the optoelectronic properties (e.g., band gap, transition dipole matrix elements, carrier effective masses, band width) through a simple band structure parameter. Our results show that reducing the splitting energy $|\Delta c|$ of p orbitals of B-site atom can effectively reduce the band gap and carrier effective masses while greatly improving the optical absorption in the visible region. Thereby, the orbital-property relationship with $\Delta c$ is well established through biaxial compressive strain. Finally, it is shown that this approach can be reasonably extended to several other non-cubic halide perovskites with similar p orbitals characteristics at the conduction band edges. Therefore, we believe that our proposed orbital engineering approach provides atomic-level guidance for understanding and optimizing the device performance of layered perovskite solar cells

Chemical Switching Behaviour of Tricarbonylrhenium(I) Complexes of a New Redox Active ‘Pincer’ Ligand

The structures and optoelectronic properties of tricarbonylrhenium(I) complexes of di(2-pyrazolyl-p-tolyl)amine in its neutral and deprotonated (uninegative amido) form were investigated. Reactions of the complexes with Brønsted acids or bases result in distinctive changes of colour and electrochemical activity owing to the non-innocent nature of the ligand

Covalently Binding the Photosystem I to Carbon Nanotubes

We present a chemical route to covalently couple the photosystem I (PS I) to carbon nanotubes (CNTs). Small linker molecules are used to connect the PS I to the CNTs. Hybrid systems, consisting of CNTs and the PS I, promise new photo-induced transport phenomena due to the outstanding optoelectronic properties of the robust cyanobacteria membrane protein PS I