Faculty Publications
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Item Defect-mediated time-efficient photocatalytic degradation of methylene blue and ciprofloxacin using tungsten-incorporated ternary perovskite BaSnO3 nanoparticles(Elsevier Ltd, 2024) Jayavelu, Y.; Maharana, G.; Rajender, G.; Reddivari, R.; Divyadharshini, S.; Baby, B.H.; Kovendhan, M.; Fernandes, J.M.; Joseph, D.P.Photocatalytic water purification has been extensively explored for its economic, eco-friendly, and sustainable aspects. In this study, tungsten (W) incorporated BaSn1-xWxO3 (x = 0 to 0.05) nanoparticles synthesized by facile hydrogen peroxide precipitation route has been demonstrated for photocatalytic degradation of methylene blue (MB) dye and ciprofloxacin (CIP) antibiotic. The structural analysis indicates the presence of hybrid composite-like nanostructures with reduced crystallinity. Optical studies reveal blueshift in bandgap and decrease in oxygen vacancy defects upon W-incorporation. Pure BaSnO3 shows overall enhanced photocatalytic activity towards MB (90.22%) and CIP (78.12%) after 240 min of white LED light and sunlight irradiation respectively. The 2 % W-incorporated BaSnO3 shows superior photocatalytic degradation of MB (26.89%) and CIP (45.14%) within first 30 min of irradiation confirming the presence of W to be beneficial in the process. The free radical study revealed the dominant role of reactive hole (h+) and oxygen radical (O2•−) species during photodegradation and their intermediates are investigated to elucidate the degradation mechanism of MB within 30 min of irradiation. This study is promising towards developing defect mediated and time-efficient photocatalysts for environmental remediation. © 2024 Elsevier LtdItem Photocatalytic Degradation of Chlorpyrifos and Tetracycline in Aqueous Medium Using Silver Titanate Perovskite Nanoparticles(Springer Science and Business Media Deutschland GmbH, 2024) Joseph, A.; Raval, K.; Manirethan, V.Near-infrared (NIR) active silver titanate perovskite (AgTiO3)-based photocatalysis is a potential method for degrading organic pollutants due to its unique structural features, compositional flexibility, and affordability. Herein, we have synthesized novel NIR-active AgTiO3 nanoparticles with a low band gap of 0.92 eV via the hydrothermal method using Ananas comosus leave extract, which is a major agricultural waste worldwide. The produced AgTiO3 nanoparticles were characterized using Fourier Transform Infrared (FTIR) spectroscopy investigations, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDS). The photocatalytic activities of the AgTiO3 nanoparticles toward the degradation of tetracycline and chlorpyrifos under UV, visible, NIR, and solar light irradiation were carefully examined, and the photocatalytic mechanism was proposed using liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography (HPLC). AgTiO3 nanoparticles completely degraded tetracycline and chlorpyrifos within 27 min and 21 min, respectively. The increased efficiency of AgTiO3 nanoparticles produced by green synthesis over conventional photocatalysts points to a potential advancement avenue for water treatment systems. Furthermore, using agricultural waste like leftover pineapple leaves not only lessens the impact on the environment but also solves the issue of cost when putting these technologies into practice on a larger scale. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Item Insights into the potential of Sb alloyed Cu2AgBiI6-based solar cells: For efficient indoor energy-harvesting(Elsevier Ltd, 2025) Kumar, A.; Siddharth, G.; Dwivedi, P.; Pandey, S.K.; Sengar, B.S.; Garg, V.Recently, indoor photovoltaics have attracted significant attention due to their remarkable capability to generate power from indoor light sources. This work investigates the performance of perovskite-inspired material Sb alloyed Cu2AgBiI6 (CABI-Sb) based indoor photovoltaic device, which has shown a power conversion efficiency of 9.53 %, reported in a recent experimental study by B. Al-Anesi et al. The baseline model of the CABI-Sb device structure (FTO/TiO2/CABI-Sb/Spiro-OMeTAD/Au) is developed in SCAPS-1D using the earlier reported experimental data. Baseline model parameters under WLED illumination are Jsc: 128.2 µA/cm2, Voc: 0.51 V, FF: 66.57 %, and PCE: 9.53 %, with a minor deviation of less than 1 %, which validates the developed model with experimental data. The performance of the device is fine-tuned by optimizing 1) Absorber thickness and defect density 2) Electron Transport Layer (ETL) doping density, conduction band offset (CBO) and interface defect density between the ETL/absorber (TiO2 /CABI-Sb) interface, 3) Hole Transport Layer (HTL) doping density, valence band offset (VBO) and interface defect density between HTL/absorber (CABI-Sb/Spiro-OMeTAD) interface, 4) work function of contacts, and 5) Series and shunt resistance were optimized. The performance parameters of the optimized device under the WLED illumination are Jsc: 1.84 mA/cm2, Voc: 1.60 V, FF: 86.78 %, and PCE: 49.31 %. A remarkable improvement in PCE is achieved from 9.53 % to 49.31 %. Further, to validate the suitability of the optimized device under different indoor environments, optimized device performance is evaluated under different lux intensities of WLED (6500 K), WLED (2700 K), compact fluorescent light (CFL), and halogen. © 2024 International Solar Energy SocietyItem An Intricate Balance of Ionicity and Covalency: Metal-Like Conduction in All-Inorganic Halide Double Perovskite Cs2AgSbCl6(American Chemical Society, 2025) Kalyani, M.; Ananthram, K.S.; Saha, S.; Ninawe, P.; Tarafder, K.; Ballav, N.Halide perovskites have recently evolved as attractive materials with enormous technological significance due to synthetic control over the structure-property relationship. Halide perovskites are often realized to be either electrical insulators or semiconductors. We present an unusual metal-like conduction (thermally deactivated) in a Pb-free all-inorganic halide double perovskite, Cs2AgSbCl6. The experimental results were understood using density functional theory studies, combined with molecular dynamics simulations and electron localization function calculations, revealing retention of the predominant ionicity of the Ag-Cl bond and an increase in the covalency of the Sb-Cl bond at an elevated temperature, which resulted in a significant change of the electronic band structure, including the density of states, thereby exhibiting an intricate balance of ionicity and covalency. A significant modulation of the electrical conductivity (more than 3 orders of magnitude) without any noticeable structural change will stimulate the investigation of hitherto unknown electronic phase transitions in halide double perovskites. Additionally, light-induced unidirectional rectification of current in Cs2AgSbCl6 was ascribed to a dynamic internal polarization effect. © 2025 American Chemical Society.Item Dopant-free hydrophobic fluorene-based hole transport materials: impact of methoxy-substituted triphenylamine and carbazole peripheral groups on the performance of perovskite solar cells(Royal Society of Chemistry, 2025) Bhat, V.G.; Keremane, K.S.; Subramanya, K.S.; Archana, S.; Hegde, A.; Asuo, I.M.; Poudel, B.; Udayakumar, U.Hole-transporting materials (HTMs) are crucial for charge separation in perovskite solar cells (PVSCs). Besides possessing suitable HOMO/LUMO energies, HTMs should ideally be hydrophobic to protect the perovskites from atmospheric moisture to enhance device stability. We designed two fluorene-core D-?-D-type organic HTMs (V1 and V2), consisting of either 4,4?-methoxy triphenylamine (V1) or N-phenyl-3,6-methoxy carbazole (V2) as the peripheral donor moiety. Optoelectronic characterization and density functional theory calculations confirmed the intramolecular charge transfer within these new HTMs. UPS and REELS analyses revealed favorable HOMO-LUMO energy level alignment of V1 and V2 with the work functions of MAPbI3 and gold electrode for effective charge extraction. TRPL and transient absorption studies commendably explained better quenching of perovskite's luminescence by V1 over V2, suggesting a better interfacial contact of V1 with the perovskite layer. Accordingly, the PVSCs with V1 and V2 as HTMs in an architecture ITO/SnO2/MAPbI3/HTM(V1 or V2)/Au demonstrated power conversion efficiency (PCE) of 14.05% and 12.73% respectively. Also, the device with V1 retains 75% of its initial efficiency for more than 480 hours. The contact angle measurements revealed the strong hydrophobicity of both alkylated fluorene molecules (V1 and V2), and impedance spectroscopy measurements further revealed higher Rrec values for these HTMs, indicating improved charge transport and reduced recombination losses. These findings demonstrate the potential of the newly developed hydrophobic fluorene-based HTMs for achieving long-lasting performance in PVSCs. © 2025 The Royal Society of Chemistry.Item A Molecular-Level Exploration of Dopant-Free Pyrazine-Derived Hole Transport Materials: Investigation of Interfacial Interaction in Perovskite Photovoltaics(John Wiley and Sons Inc, 2025) Sheshachala, A.; Keremane, K.S.; Bhat, V.G.; Karunakar Shankar, S.; Asuo, I.M.; Doumon, N.Y.; Poudel, B.; Udayakumar, U.The development of innovative core structures and peripheral groups for organic hole-transporting materials (HTMs) continues to be a focal point in enhancing the performance of perovskite solar cells (PVSCs). This study reports the design and synthesis of dopant-free pyrazine-based HTMs. PS1 features a D–A–D type structure with pyrazine as the acceptor and 4,4?-dimethoxy triphenylamine (4,4?-OMe-TPA) as the donor, while PS2 adopts a D–?–A–?–D configuration with an additional thiophene unit as ?-spacer along with 4,4?-OMe-TPA as donor. Both compounds are synthesized through a simple two-step synthetic procedure. These HTMs are subjected to structural, photophysical, electrochemical, theoretical, and photoelectrochemical studies with an emphasis on evaluation of structure–property relationships. Theoretical studies are conducted to explore the electronic distribution, optimized molecular structure, and frontier molecular orbitals. Their performance in PVSCs is systematically evaluated without adding dopants. PS2 exhibits superior photoluminescence quenching compared to PS1, indicating more efficient charge transfer from the perovskite layer. Notably, PS2 achieves a power conversion efficiency (PCE) of 11.9%, surpassing the performance of PS1 (PCE of 10.15%). These findings highlight the potential of adjusting the electron-deficient core and ?-bridge units as an effective strategy to optimize the properties of HTMs and improve their performance in PVSC applications. © 2025 Wiley-VCH GmbH.