Browsing by Author "Thiyyakkandy, J."

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    Comprehensive Modeling of High-Performance All-Inorganic Cs2TiBr6-Based Perovskite Solar Cells
    (John Wiley and Sons Inc, 2024) Kumar, S.; Thiyyakkandy, J.; Yadav, A.K.; Vinturaj, V.; Garg, V.; Prabhu, S.; Pandey, S.K.
    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. © 2024 Wiley-VCH GmbH.
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    Optimization of Quantum Capacitance of Functionalized VS2 Monolayer Electrodes to Shrink Hybrid Supercapacitors for On-Chip Energy Sources
    (American Chemical Society, 2025) Yadav, A.K.; Thiyyakkandy, J.; Singh, R.; Das, P.P.; Ajith, K.M.; Pandey, S.K.
    Quantum capacitance (CQ) of the electrodes plays an important role in enhancing the performance of supercapacitors by directly affecting the overall capacitance. In this study, several approaches including doping, creating vacancy, and adsorption have been used to enhance the CQ of the vanadium disulfide (VS2) electrode using density functional theory calculation. The undoped VS2 monolayer shows a maximum CQ value of 20.19 ?F/cm2. After creating V-vacancy (Vv) in the VS2 monolayer lattice, the CQ value increased to 35.61 ?F/cm2, which is the highest among all doped and defective VS2 lattices at room temperature. When we use VS2 electrodes for supercapacitors, generally ion adsorption occurs at the electrode surface, showing the necessity to investigate the adsorption of alkali/alkaline atoms (Li, Na, K, and Mg) at the VS2 surface to know the change in different properties of the electrode. It is found that generally CQ reduces due to the adsorption of alkali/alkaline atoms at the surface, but the K-adsorption at S-vacancy (Vs) VS2 demonstrated the increment of CQ value from 21.75 to 35.32 ?F/cm2 at room temperature. Additionally, the variation of the adsorption distance of the K atom at the Vs-VS2 surface revealed an optimum distance of value 3.5 Å, indicating that the K atom (radius = 2.43 Å) stabilizes just above the VS2 surface. Moreover, augmentation in CQ was seen with a decrease in temperature and attained a value of 49.96 ?F/cm2 at 100 K. The calculated CQ and open-circuit voltage (OCV) duly confirmed that the K-adsorbed Vs-VS2 is a potential candidate for the anode of hybrid supercapacitors as it has a maximum CQ value at the positive side of the electrochemical potential and an average OCV value of +0.615 V. This study reveals that the CQ of the VS2 electrode can be increased to minimize the size of high-performance hybrid supercapacitors for its application as an on-chip energy source. © 2025 American Chemical Society.