Gas sensing mechanism of H 2 S, NH 3 , NO 2 and NO toxic gases on transition metal dichalcogenides based Janus MoSSe monolayers are investigated using the density functional theory. The pristine and defect included MoSSe layers are considered as a host material for adsorption study. Three types of defects (i) molybdenum vacancy, (ii) selenium vacancy, and (iii) sulfur/selenium vacancy are studied to understand their impact on electronic properties and sensing of these gas molecules. The formation energy is computed to predict the stability of these defects and noticed that selenium vacancy is the most stable among other defects. The adsorption of gas molecules is evaluated in terms of adsorption energy, vertical height, charge difference density, Bader charge analysis, electronic and magnetic properties. The maximum adsorption energy for H 2 S, NH 3 , NO 2 and NO molecules on pristine Janus MoSSe monolayer are ~ -0.156eV, -0.203eV, -0.252eV, and -0.117eV, respectively. Selenium and sulfur/selenium defects significantly improve the sensing of the gas molecules. NO 2 gas molecule dissociates and forms oxygen doped NO adsorption in selenium and sulfur/selenium defect included MoSSe Janus monolayer. The adsorption energy values are ~ -3.360eV and -3.404eV for Se and S/Se defects included MoSSe layer, respectively. Further, the adsorption of NO 2 molecule induced about 1µ B magnetic moment. In contrast, NO molecule showed chemisorption on the surface of the selenium and sulfur/selenium defect included Janus MoSSe monolayers, whereas H 2 S and NH 3 molecules showed physisorption with their adsorption energies in the range of -0.146 to -0.238 eV and -0.140 to -0.281 eV, respectively. The adsorption of H 2 S, NH 3 , NO 2 and NO molecule on the pristine and defected monolayers suggest that selenium and sulfur/selenium vacancy defects are more prominent for NO 2 and NO gas molecule adsorption.

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We demonstrated ultrahigh sensitivity with excellent recovery time for H₂S, NH₃, NO₂, and NO molecules on the sulfur and selenium surfaces of Janus WSSe monolayers using density functional theory.

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The development of an efficient blue phosphor with remarkable thermal stability required for high-quality white-lightemitting diodes (WLEDs) remains an exigent task and mainly concerned BaMgAl 10 O 17 :Eu 2+ (BAM:Eu). Despite the outstanding performance of BAM:Eu, the reduction in luminescence efficiency under long-term operation results in numerous researches on new hosts having lattice rigidity with symmetrical coordination environment. Therefore, we have synthesized a competent blue-emitting Eu 2+ -activated Sr 5 SiO 4 Cl 6 (SSC) phosphors. The admirable rigidity of these phosphors with three Sr polyhedra Sr(I)O 9 , Sr(II)O 7 , and Sr(III)O 8 assessed from Rietveld refinement indicate the dense connectivity in the crystal structure, and the ab initio calculations further support the firm electronic band structure. The broad excitation from 250 to 450 nm suitably matches the absorption band of a near-UV (n-UV) LED chip. The phosphor exhibited bright blue emission with internal quantum yield and color purity > 90% which contribute to the slender fwhm of 33 nm. The firstprinciple calculation indicates the most stable site for Eu 2+ substitution as Sr(III)O 8 , and the experimental results agreed with this fact as well. The synthesized phosphor displayed an excellent thermal stability which is superior to that of the commercial BAM:Eu phosphor. The excellent thermal stability may be owed to the highly symmetric coordination environment of Eu 2+ in the SSC host that are revealed from the distortion and charge density distribution calculation by density functional theory. The blue phosphor was further utilized for WLEDs and displayed white light with a high color-rendering index and suitable correlated color temperature, which is ideal for practical applications in warm WLEDs.

Organic–inorganic perovskite solar cells (PSCs) have shown tremendous progress from 3.8% power conversion efficiency (PCE) in 2003 to 25.2% in 2020 because of their wide range of light absorption, fast charge separation, long carrier diffusion length, and long carrier lifetime. The optoelectronic characteristics of hole transport material (HTM) and electron transport material (ETM) strongly affect photovoltaic (PV) performance and stability of PSCs. Recently, various inorganic HTMs with high efficiency, stability, and cost‐effectiveness have been investigated. Among them, nickel oxide (NiO x ) is one of the most studied inorganic HTMs in terms of device performance and stability because it has high hole mobility, electrical conductivity, transmittance, and energetically favorable band alignment, along with environmental stability. This article overviews the recent progress on NiO x ‐based planar PSCs. The main focus is on the structural, electrical and optical properties of the NiO x thin film, which mainly depends on the synthesis methods and post‐treatments. Firstly, a variety of methods are investigated to fabricate dense, compact and high crystallized NiO x thin film. Moreover, multifarious doping strategies and surface functionalization using organic materials are summarized as approaches to improve their properties for realizing high performance p–i–n planar PSC devices.

Herein, we synthesized Sb-based single crystals (SCs) of Cs2AgSbCl6 with an impressive low bandgap of ∼1.82 eV and demonstrated the effect of strain on optical properties. Interestingly, the polycrystalline ground powder and the heated SCs of Cs2AgSbCl6 exhibited a larger bandgap of ∼2.55 eV. The reduction of bandgap is attributed to the existence of strain in the SC as confirmed by X-ray diffraction and Raman spectroscopy and supported by density functional theory (DFT) calculations. The strain engineering for bandgap reduction can play a pivotal role for developing low-bandgap lead-free double perovskite for environmentally friendly solar cell applications.