Excitonic effects in absorption spectra of carbon dioxide reduction photocatalysts

The formation and disassociation of excitons play a crucial role in any photovoltaic or photocatalytic application. However, excitonic effects are seldom considered in materials discovery studies due to the monumental computational cost associated with the examination of these properties. Here, we study the excitonic properties of nearly 50 photocatalysts using state-of-the-art Bethe–Salpeter formalism. These ~50 materials were recently recognized as promising photocatalysts for CO2 reduction through a data-driven screening of 68,860 materials. Here, we propose three screening criteria based on the optical properties of these materials, taking excitonic effects into account, to further down select six materials. Furthermore, we study the correlation between the exciton binding energies obtained from the Bethe–Salpeter formalism and those obtained from the computationally much less-expensive Wannier–Mott model for these chemically diverse ~50 materials. This work presents a paradigm towards the inclusion of excitonic effects in future materials discovery for solar-energy harvesting applications.

Исследование процесса локального анодного окисления тонких пленок GeO и создание наноструктур на их основе

The process of local anodic oxidation of thin GeO films has been studied using an atomic force microscope. The electron-probe microanalysis showed that oxidized areas of a GeO film were germanium dioxide. The effect of the voltage pulse duration applied to the probe–substrate system and the atmospheric humidity on the height of the oxide structures has been studied. The kinetics of the local anodic oxidation (LAO) in a semi-contact mode obeys the Cabrera–Mott model for large times. The initial growth rate of the oxide ( R _0) significantly increases and the time of starting the oxidation ( t _0) decreases as the atmospheric humidity increases by 20%, which is related to an increase in the concentration of oxygen-containing ions at the surface of the oxidized GeO film. It was shown that nanostructures in thin GeO layers can be formed by the LAO method.

Compositional Dependence of Optical Absorption in Barium Oxychloride Borate Glasses

The present communication deals with some significant results pertaining to the optical absorption analysis of glasses in the compositional range of xBaCl2·(30–x)·BaO·68B2O3·2V2O5 (x = 0, 5, 7 and 10 mol%) prepared via convenient melt-quench route. The optical absorption data recorded in wavelength range of 200–800 nm is analyzed by means of Davis-Mott model to evaluate optical band gaps corresponding to direct and indirect transitions. The absorption tail is analyzed to obtain Urbach's energy. Behavioral change in optical band gap and Urbach's energy with changing chlorine concentrations is discussed to predict the structural changes governed in the glass matrix.

Electric and photoelectric properties of solid solutions Ag2In2Si(Ge)Se6

Temperature depen-dences of specific dark conductivity and spectral distributions ofphotoconductivity have been studied. It has been established thatthe Ag2In2SiSe6and Ag2In2GeSe6single crystals are high-resistancesemiconductors withp-type conductivity. The interpretation of experimental results conducted under the Mott model for disordered systems. Thus, from the experimental results follows that the solid solution AgInSe2 - Si(Ge)Se2 when the temperature drops from 300 to 200 K, the conductivity in the area carried thermo excited permitted carriers impurity activation energy of ~ 0.59eV and 0.48eV for Ag2In2SiSe6 and Ag2In2GeSe6 respectively.

Optical Characterization of Thiophene Blending with Non-Conjugated Polymer at Different Composition

Thin film conducting polymer thiophene based that is poly(3,4-ethylenedioxythiophene): poly(styrene sulphonic acid) (PEDOT:PSS) blended with Polyaniline (PANi) have been prepared with different composition by using drop casting technique. The optical characterization has been done by analyzing the absorbance spectra in the wavelength 300 to 800 nm. The electronic parameters were calculated by using Tauc/Davis-Mott Model. The results obtained showed that the absorbance, optical energy and Urbach energy were dependence on the ratio of PEDOT: PSS to PANi compositions.