• Energy Research

In this work, studies of the optical constants of monolayer transition metal dichalcogenides and few-layer black phosphorus are briefly reviewed, with particular emphasis on the complex dielectric function and refractive index. Specifically, an estimate of the complex index of refraction of phosphorene and few-layer black phosphorus is given. The complex index of refraction of this material was extracted from differential reflectance data reported in the literature by employing a constrained Kramers–Kronig analysis combined with the transfer matrix method. The reflectance contrast of 1–3 layers of black phosphorus on a silicon dioxide/silicon substrate was then calculated using the extracted complex indices of refraction.

This review describes hybrid photonic-plasmonic structures based on periodic structures that have metallic coatings or inserts which make use of the Tamm plasmon for sensing applications. The term Tamm plasmon refers a particular resonance resulting from the enhancement of a surface plasmon resonance absorption via coupling to a wavelength-matching photonic bandgap provided by a photonic crystal. Tamm plasmon-based devices come in an ample variety of material and geometric combinations, each designed to perform a specific kind of measurement. While the physical effect is quite well documented and understood, its implementation in devices is still a rapidly developing and thriving field, which leaves open many possibilities for novel designs and new applications. We therefore aim of giving a complete overview on the topic, so as to provide an ordered collection of designs and uses, as well as to spur further development on the subject of the Tamm plasmon for sensing applications.

‘Soft’ nanoparticles for low temperature processes and highly efficient water-processed organic solar cells.

In this work, we study the light absorption properties of different novel molecules based on benzo[1,2-b:4,5-b′]dithiophene (BDT), namely, BT-2F, BTRCl, and BTTzR, which hold great promise as electron-donor materials in organic solar cells. By employing density functional theory, we study the electronic states and related transitions in these systems. Moreover, in the case of BTTzR, we observe that the addition of two and three oligothiophene chains to the central benzene ring of the BDT unit leads to both a red-shift of the existing peaks and, interestingly, the development of new blue-shifted features, an effect that permits to enhance the panchromaticity of the molecule in the visible spectral range, thus rendering these new derivatives highly appealing as light absorbers in organic solar cells.

AbstractA series of zigzag‐edged polycyclic aromatic hydrocarbons (PAHs) (Z1‐Z3) were synthesized from 2,12‐dibromo‐7,14‐diphenyl‐benzo[m]tetraphene (9) as a versatile building block. Their structures were unambiguously confirmed by laser desorption/ionization time‐of‐flight mass spectrometry, 1H NMR, Raman, and Fourier‐transformed infrared (FTIR) spectroscopies as well as scanning tunneling microscopy. The fingerprint vibrational modes were elucidated with theoretical support. The edge‐ and size‐dependent optical properties were characterized by UV‐Vis absorption and fluorescence spectroscopy and DFT calculations. Moreover, ultrafast transient absorption spectroscopy revealed distinct modulation of the photophysical properties upon π‐extension from Z1 to Z2, the latter having a gulf edge.

A π-extended double [7]carbohelicene 2 with fused pyrene units was synthesized, revealing considerable intra- and intermolecular π-π interactions as confirmed with X-ray crystallography. As compared to the previous double [7]carbohelicene 1, the π-extended homologue 2 demonstrated considerably red-shifted absorption with an onset at 645 nm (1: 550 nm) corresponding to a smaller optical gap of 1.90 eV (1: 2.25 eV). A broad near-infrared emission from 600 to 900 nm with a large Stokes shift of ∼100 nm (2.3 × 103 cm-1) was recorded for 2, implying formation of an intramolecular excimer upon excitation, which was corroborated with femtosecond transient absorption spectroscopy. Moreover, 2 revealed remarkable chiral stability with a fairly high isomerization barrier of 46 kcal mol-1, according to density functional theory calculations, which allowed optical resolution by chiral HPLC and suggests potential applications in chiroptical devices.