Sb2Se3 as an HTL for Mo/Sb2Se3/Cs2TiF6/TiO2 solar structure: performance evaluation with SCAPS-1D.

Perovskite-based solar cells (PSCs) have recently gained much attention due to their distinctive optical and electrical properties. Cesium titanium fluoride (Cs2TiF6) is an example of lead-free perovskite absorber material with a bandgap of 1.9 eV, making it suitable for a solar device. However, the high cost of the hole transport material (HTM) and other considerations prevent their commercial production. Antimony selenide (Sb2Se3) is well suited for HTM as it is low-cost material with a tunable bandgap. The work presents the TiO2/Cs2TiF6/Sb2Se3-based solar cell performance using SCAPS-1D simulation software. The effect of all the active layer thicknesses, defect density, hole-electron mobility, and temperature on the device is also simulated. I-V, C-V, and QE curves and energy band diagrams show the photovoltaic device's excellent performance. The outputs are competent enough with an efficiency of 22.10 % when Sb2Se3 is used as a hole transport layer (HTL) in the device architecture. The results suggest that the lead-free solar cell is a promising future option for the solar cell community regarding environmental friendliness and high efficiency.

Synthesis, Characterization and Sun Light-Driven Photocatalytic Activity of Zinc Oxide Nanostructures.

Low-temperature growth of nanostructures with large yield is a basic requirement for fulfilling the demand of large-scale applications of nanomaterials. The synthesis of nanoscale materials has gained considerable attention due to their excellent properties also in photocatalysis. Catalyst and Dopant free, solar active ZnO nanostructures photocatalysts with vacancy richness were synthesized in large quantities (in grams) through the co-precipitation growth process using ZnNi2·6H2O as the zinc source at room temperature. This method has advantages such as low temperature with high yield (>8 grams per liter) at atmospheric pressure synthesis. The experimental results confirm that synthesized ZnO samples were crystallized into a wurtzite hexagonal structure. Under direct sunlight energy examined degradation of organic dye methylene blue (MB) for photocatalytic activity using ZnO nanostructures. The photocatalytic performance depends on the different defects as well as the specific surface area. After photocatalytic degradation of MB dye in 60 min under natural sunlight irradiation colorless matrix was observed. The repeatability assessments for reusability of ZnO nanostructures after photocatalytic activity was also studied and reported for degradation of organic MB dye.

Correlation of growth temperature with stress, defect states and electronic structure in an epitaxial GaN film grown on c-sapphire via plasma MBE.

The relationship of the growth temperature with stress, defect states, and electronic structure of molecular beam epitaxy grown GaN films on c-plane (0001) sapphire substrates is demonstrated. A minimum compressively stressed GaN film is grown by tuning the growth temperature. The correlation of dislocations/defects with the stress relaxation is scrutinized by high-resolution X-ray diffraction and photoluminescence measurements which show a high crystalline quality with significant reduction in the threading dislocation density and defect related bands. A substantial reduction in yellow band related defect states is correlated with the stress relaxation in the grown film. Temperature dependent Raman analysis shows the thermal stability of the stress relaxed GaN film which further reveals a downshift in the E2 (high) phonon frequency owing to the thermal expansion of the lattice at elevated temperatures. Electronic structure analysis reveals that the Fermi level of the films is pinned at the respective defect states; however, for the stress relaxed film it is located at the charge neutrality level possessing the lowest electron affinity. The analysis demonstrates that the generated stress not only affects the defect states, but also the crystal quality, surface morphology and electronic structure/properties.

Enhanced spin-orbit coupling and charge carrier density suppression in LaAl1-xCrxO3/SrTiO3 hetero-interfaces.

We report a gradual suppression of the two-dimensional electron gas (2DEG) at the LaAlO(3)/SrTiO(3) interface on substitution of chromium at the Al sites. The sheet carrier density at the interface (n□) drops monotonically from ∼2.2 × 10(14) cm(-2) to ∼2.5 × 10(13) cm(-2) on replacing ≈60% of the Al sites by Cr and the sheet resistance (R□) exceeds the quantum limit for localization (h/2e(2)) in the concentrating range 40-60% of Cr. The samples with Cr ⩽40% show a distinct minimum (T(m)) in metallic R□(T) whose position shifts to higher temperatures on increasing the substitution. Distinct signatures of Rashba spin-orbit interaction (SOI) induced magnetoresistance (MR) are seen in R□ measured in out of plane field (H⊥) geometry at T ⩽ 8 K. Analysis of these data in the framework of Maekawa-Fukuyama theory allows extraction of the SOI critical field (H(SO)) and time scale (τ(SO)) whose evolution with Cr concentration is similar as with the increasing negative gate voltage in LAO/STO interface. The MR in the temperature range 8 K ⩽ T ⩽ T(m) is quadratic in the field with a +ve sign for H⊥ and -ve sign for H∥. The behaviour of H∥ MR is consistent with Kondo theory which in the present case is renormalized by the strong Rashba SOI at T < 8 K.

Crystalline perfection, optical and third harmonic generation analyses of non-linear optical single crystal of L-lysine acetate.

The potential organic non-linear optical single crystal of L-lysine acetate has been grown by slow evaporation solution growth technique (SEST) at room temperature. It crystallizes in the monoclinic system with space group of P2(1). The crystalline perfection of the grown single crystal has been examined by high resolution X-ray diffraction analysis (HRXRD). The functional groups of the synthesized compound have been identified by (13)C NMR, (1)H NMR and FTIR analyses. The optical absorption studies show that the crystal is transparent in the entire visible region with a cut-off wavelength of 236 nm. The optical band gap is found to be 5.29 eV. The steady-state PL spectra was recorded for pure L-lysine acetate crystal at room temperature. The third harmonic generation efficiency of the crystal has been evaluated by Z-scan technique and its non-linear optical coefficient has been calculated. Birefringence measurement has been carried out in order to see the optical homogeneity of the grown specimen. Its electrical properties has been assessed by dielectric measurement at different temperatures. The calculated optical band gap is 5.29 eV. Its thermal parameters like thermal diffusivity (α), thermal effusivity (e), thermal conductivity (k) and heat capacity (C(p)) have been determined by photopyroelectric technique. Vickers micro hardness studies were carried out using a Vickers hardness tester equipped with a diamond square indenter. The piezoelectric measurement for L-lysine acetate has been also been carried at ambient condition.

Studies on the effect of polymer coating on solution grown hygroscopic non-linear optical single crystal of L-lysine monohydrochloride.

Nonlinear optical single crystals are getting attention because of its enormous applications in the area of fiber optic communication and optical signal processing. In this article, we are reporting the single crystal growth of l-lysine monohydrochloride by slow evaporation solution growth technique, by using double distilled water as the solvent. We found that the grown single crystal is bulk in size and fairly transparent. But after a period of time, due to its hygroscopic nature, the transparency is completely vanished and became opaque. Then we have attempted to coat the poly methyl methacrylate (PMMA) polymer on the surface of l-lysine monohydrochloride (l-LMHCL) single crystal by dip coating method. This polymer coating is giving resistance to hygroscopic nature and also acting as thin protective covering layer without affecting the other properties. Then we have systematically studied the different properties of bare, polymer coated and hygroscopic l-LMCHL single crystals. Its crystalline perfection was examined by high resolution X-ray diffractometer and found major differences in crystalline quality. Its structural and optical behavior was assessed by powder X-ray diffraction, UV-vis and luminescence analyses.