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The perovskites are desirable materials for photovoltaic and other renewable green energy technologies. Lead‐based perovskite solar cells (PSC) have recently gained considerable attention due to the abrupt rise in power conversion efficiency, but lead's well‐known toxicity prevents its large‐scale commercialization. One compelling option is Cs2TiBr6, which offers a nontoxic alternative. Herein, the electronic and optical characteristics of Cs2TiBr6 absorber material using density functional theory employing the WIEN2K tool are investigated. The energy band structure of Cs2TiBr6 shows an indirect bandgap of 2.2 eV. Additionally, optical properties are calculated, and the suitability of this material as an absorber for indoor and outdoor photovoltaic devices is investigated. The Cs2TiBr6 material has a peak absorption coefficient of 39.57 × 104 cm−1 and optical conductivity of 1.98 × 1015s−1, demonstrating its suitability as an absorber material. After that, a PSC is modeled using SCAPS‐1D by using the computed parameters. The performance of the modeled perovskite is enhanced by optimization of various parameters, resulting in the achievement of a high‐performance Cs2TiBr6‐based PSC, boasting a power conversion efficiency of 19.9% for air mass AM1.5 G spectra and power conversion efficiency of 16.76% for light emitting diode and 17.18% for incandescent light for indoor light conditions. [ABSTRACT FROM AUTHOR]

Context: Carbon monoxide, also known as the "silent killer," is a colorless, odorless, tasteless, and non-irritable gas that, when inhaled, enters the bloodstream and lungs, binds with the hemoglobin, and blocks oxygen from reaching tissues and cells. In this work, the monolayer MoSe2-based CO gas sensors were designed using density functional theory calculation with several dopants including Al, Au, Pd, Ni, Cu, and P. Here, Cu and P were found to be the best dopants, with adsorption energies of −0.67 eV (Cu) and −0.54 eV (P) and recovery times of 1.66 s and 13.8 ms respectively. Cu conductivity for CO adsorption was found to be 2.74 times that of CO2 adsorption in the 1.0–2.26 eV range. P displayed the highest selectivity, followed by Pd and Ni. The dopants, Pd and Ni, were found suitable for building CO gas scavengers due to their high recovery times of 9.76 × 1020 s and 2.47 × 1011 s. Similarly, the adsorption of CO2 on doped monolayer MoSe2 was also investigated. In this study, it is found that monolayer MoSe2 could be employed to create high-performance CO sensors in a CO2-rich environment. Method: The electrical characteristics of all doped MoSe2 monolayers are obtained using a DFT calculation with the PBE-GGA method from the Quantum ESPRESSO package. The self-consistent field (SCF) computations were performed using a 7 × 7 × 1 k-point grid and a norm-conserving pseudo potential (NCPP) file. To determine electrical conductivity, the semi-classical version of Boltzmann transport theory, implemented in the Boltz Trap code, was used. [ABSTRACT FROM AUTHOR]

Vanadium disulfide (VS2) is an important member of the transition‐metal dichalcogenides (TMDs) family, which offers high conductivity. In nature, it can exist in two phases, i.e., 1T and 2H. Herein, the metallic 1T VS2‐based in‐plane micro‐supercapacitor (MSC) is fabricated by a facile‐mask‐assisted printing technique. Initially, the 1T VS2 nanosheets are synthesized using a simple one‐pot hydrothermal route. The material characterizations have claimed the formation of a 1T phase and the density of states (DOS) reveal that the 1T phase of VS2 is metallic in nature. After experimental and theoretical investigations of synthesized nanosheets, a VS2 electrode‐based in‐plane MSC is fabricated using a simple mask‐assisted printing technique. The fabricated device demonstrates excellent capacitance retention of 97.6% after 1000 cycles of cyclic voltammetry measurement at a 100 mV s−1 scan rate. The device also shows an excellent areal capacitance of 212.7 mF cm−2 and a high areal energy density of 10.63 μWh cm−2 at a high‐power density of 4.45 mW cm−2. This low‐cost and simple fabrication process can produce high‐performance in‐plane MSC devices. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the various electronic and optical properties of undoped molybdenum diselenide (MoSe2) monolayer, such as band structure, density of states, electron density, dielectric function, refractive index, extinction coefficient, reflectivity and energy loss function using density functional theory. Additionally, substitutional doping using niobium (Nb) and manganese (Mn) atoms and introducing defects in undoped MoSe2 lattice were investigated to know the detailed effect of the same on its properties. It is found that the undoped MoSe2 monolayer demonstrates a direct energy bandgap of ~1.44 eV, which reduces after Mn, Nb doping and after introducing Mo, Se vacancy. The energy bandgap attains a very small value 0.2 eV after introducing Se vacancy defect in MoSe2 lattice. The extinction coefficient of MoSe2 monolayer demonstrates a significant increase from 1.79 to 2.66 a.u. after introducing the Mo vacancy in the undoped lattice. The variation of semiconductor to nearly semi-metallic character of MoSe2 by introducing defects makes it very suitable for the application in high-performance solar cells, photo-electrochemical cells, sensors and biosensor applications. [ABSTRACT FROM AUTHOR]

With lead-based perovskite materials, lead content and long-term stability are the big concerns. Recently, Cesium tin iodide (Cs2SnI6) double perovskite has gained recognition as a stable and environment-friendly photovoltaic material compared to lead-based perovskite materials. In the present study, we have investigated Cs2SnI6 based solar cell with all inorganic transport materials using SCAPS-1D. The optimized device exhibited a maximum efficiency of about 18%. Further we fabricated Cs2SnI6 perovskite films using a solution process approach, utilizing CsI and SnI4 in a 2:1 ratio. For synthesized double perovskite film, the crystallinity, morphologies, and optical characteristics were examined. Additionally, the stability analysis confirmed that the prepared perovskite films were stable for more than two months under ambient exposure. Finally, utilizing the synthesized Cs2SnI6 thin films as an absorber material, we fabricated two solar cells without and with hole transport layer (HTL), having configurations of glass/FTO/ZnO/Cs2SnI6/Ni and glass/FTO/ZnO/Cs2SnI6/ MoS2/Ni, respectively, in the ambient conditions. As a major finding, it has been observed that the inclusion of MoS2 as HTL improved overall performance, with an enhancement in the power conversion efficiency (PCE) of nearly 45% compared to the device without HTL. [ABSTRACT FROM AUTHOR]

Herein, the comprehensive study of different properties of undoped MoS2, MoS2 lattice with sulfur (S) and, molybdenum (Mo) vacancy, and MoS2 with substitutional doping of niobium (Nb), vanadium (V), and zinc (Zn) atoms is done. The density functional theory (DFT) is used and the electronic properties like density of states, band structure, electron density, and optical properties like dielectric function, optical conductivity, and refractive index are studied. It is observed that undoped MoS2 monolayer shows direct bandgap semiconductor characteristics with a bandgap of around 1.79 eV. P‐type characteristics are observed for Nb‐, V‐, and Zn‐doped MoS2 lattices. The real part and imaginary parts of all optical parameters along x and z directions for different MoS2 supercells are found to be anisotropic in nature up to a photon energy of almost 11 eV and thereafter they show nearly isotropic nature. Finally, it is found that the obtained properties of MoS2 monolayer as per literature are suitable for next‐generation MOSFET application. [ABSTRACT FROM AUTHOR]

The vanadium disulfide (VS2) material, a prominent member of the two-dimensional materials family, has great potential to bridge the performance gap between current performance and contemporary energy storage device needs. Here, we report the optimization of the growth temperature of VS2 monolayer crystals using a chemical vapor deposition system. It is also found the crystal size increases with the increase of growth temperature up to 770 °C. Further increasing of growth temperature resulted in a reduction of crystal size. The atomic force microscopy measurement demonstrated the growth of monolayer thick VS2 crystal. Raman spectra revealed the formation of H-phase monolayer high-quality VS2 crystals. To understand the precise impact of doping on electronic properties, the substitutional doping of VS2 monolayer with chromium, molybdenum, and tungsten was also examined using density functional theory. The VS2 monolayer exhibits an indirect energy band gap that decreases after chromium doping of the VS2 lattice and vanishes after molybdenum and tungsten doping. Finally, it is found that tungsten-doped VS2 monolayer exhibits strong metallic character and other exceptional properties, making it suitable for electrodes of various energy storage devices. [ABSTRACT FROM AUTHOR]

Summary: Kesterite Cu2ZnSnS4(CZTS) thin‐film technology has been comprehensively investigated over the last decade as a promising candidate in the field of photovoltaic technologies. However, despite numerous strategies to improve the performance, the efficiencies remain stagnant at around 11%. Poorly optimized absorber/buffer interface, non‐absorption of higher wavelength photons, and non‐ohmic back contact are the primary reasons for the poor performance of the CZTS solar cell. The authors of this paper propose a cadmium‐free buffer layer, multiple quantum wells (MQWs) structure, and a back surface field (BSF) layer to overcome these issues, respectively. In this study, the buffer layer, zinc oxysulfide (Zn[O1−xSx]) is considered as an alternative to toxic Cadmium Sulfide (CdS) for better band alignment with the CZTS absorber layer. Cu2ZnSn(SxSe1−x)4 (CZTSSe) is used as a quantum well material in MQWs to increase photon absorption in CZTS solar cells. Tin selenide (SnSe) is used as the BSF layer to reduce the effect of non‐ohmic back contact and to improve the open‐circuit voltage (Voc) of MQW incorporated CZTS solar cells. Detailed analysis and optimization of the modified structure with higher performance are presented. The simulation results obtained provide imperative guidelines for the fabrication of high‐efficiency CZTS solar cells using non‐toxic and earth‐abundant materials. [ABSTRACT FROM AUTHOR]

Recently, unprecedented interest has been immersed toward the synthesis of two-dimensional (2D) transition metal dichalcogenides via the chemical vapor deposition (CVD) system. Synthesis of a uniform and large-sized monolayer MoS2 atomic thin film via CVD is still a major bottleneck owing to strong dependence on diverse associated growth parameters. In this work, we have proposed the most viable recipe which is suitable for controlling the nucleation density of Mo and producing a 90 μm-long MoS2 monolayer crystal and (695 × 394.8) μm2 large MoS2 monolayered film on SiO2/Si and c-plane sapphire, respectively. Moreover, MoS2 monolayer sensing performance has been thoroughly investigated for NO2 exposure at room temperature with a varying response of 4–57.5 for the 100–100 ppm level. Furthermore, the MoS2 monolayer sensor exhibits an ultrasensitive NO2 detection with limit of detection and limit of qualification values of 1.4 and 4.6 ppb, respectively. In addition, the first-principles-based density functional theory has been employed to analyze the adsorption of NO2 on the surfaces of the 2D MoS2 monolayer. It is observed that the electronic band gap of the MoS2 monolayer after NO2 adsorption is reduced by 0.7 eV due to molecular orbital hybridization. [ABSTRACT FROM AUTHOR]