Indian Institute of Engineering Science and Technology, Shibpur

Future developments in perovskite solar cells (PSCs) focuses on lead-free versions because of their lower toxicity. However, lead-free PSCs' limited Power Conversion Efficiency (PCE) compared to their lead-based counterparts prevents them from being used more widely. This issue can be successfully resolved with the multi-absorber approach since it maximizes the use of the solar spectrum. Therefore, this article incorporates numerical modeling guided optimization of a lead free all inorganic ITO/ETL/CsSnI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>/CsSnCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>/HTL dual absorbers-based heterojunction structure to improve the performance of Cesium Tin Iodide (CsSnI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>) and Cesium Tin Chloride (CsSnCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>) based single absorber PSCs. The critical device's parameters, such as absorber layer and carrier transport layer thickness, defect density, temperature, doping concentration, series and shunt resistances are thoroughly optimized and evaluated using Solar cell capacitance simulator (SCAPS-1D). The proposed dual absorber composition produces a substantial enhancement in performance with PCE (η) of 24%, Short Circuit Current (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub>) of 28.5 mA/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, Open Circuit Voltage (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub>) of 0.96 V, and Field Factor (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FF</i>) of 85.87% at a device defect density of 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> outperforming the 12.96% and 9.66% of PCE attained with the reported CsSnI<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and CsSnCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> single junction counterparts.

The rise of generative AI presents a profound duality. On one hand, it offers a powerful solution to data scarcity and privacy challenges in biometrics. On the other, it is weaponized to create deepfakes that threaten digital integrity. Existing detectors for these deepfakes are brittle, failing against real-world transformations and novel generative models. This dissertation confronts this duality head-on. First, I establish the viability of synthetic data for building fair and private biometric systems. Second, to counter the malicious use of this technology, this dissertation develops deepfake detectors designed to be robust, generalizable, and efficient by construction. My work introduces novel, lightweight feature sets on different cues (e.g., colour cue-based Relative Chrominance Difference, Gradient features, Depth cues, etc.) that are inherently resilient to OSN transformations and improve generalisation to unseen forgeries. Whereas, accomplished results confirm state-of-the-art performance, achieving high accuracy in challenging real-world scenarios with a significant reduction in model complexity, my current and future work focuses on achieving superior generalisation while being OSN manipulation resistant.

Drought, a multifaceted natural hazard, arises not only from extended periods of below-average precipitation, but also from anthropogenic exploitation of terrestrial water storage (TWS), and is affecting the agriculturally intensive Ganga-Brahmaputra Basin (GBB). Hence this study explores the drought scenario of GBB using a combined drought index which uses both precipitation and GRACE-derived total water storage anomaly (TWSA) as the indicators. Furthermore, the relative contribution of TWSA and precipitation anomaly is envisaged in this research to quantify the dominant contributor of drought in the basin. The results reveal a marked decline in TWSA across all sub-basins, with the Upper Ganga Basin (UGB) and Yamuna-Chambal Basin (YCB) exhibiting the sharpest declines of -2.622 cm/year and − 2.116 cm/year, respectively, largely driven by unsustainable groundwater extraction and climatic variability. In contrast, the Lower Ganga Basin (LGB) and Brahmaputra Basin (BB) experience slower declines in TWSA, at -0.840 cm/year and − 1.065 cm/year, owing to their distinct aquifer characteristics and higher precipitation levels. The Combined Climatologic Deviation Index (CCDI), used to identify the drought scenario of the basins, showed significant parts of YCB and UGB faced the most severe long-duration droughts. Relative importance analysis underscores the dominant role of TWSA in shaping drought severity, with greater influence than precipitation anomalies in UGB and YCB, while LGB and BB have much influence on precipitation. Drought propagation times representing catchment response vary significantly among basins, with UGB and YCB exhibiting rapid response to input precipitation (5–6 months), while LGB shows a slower response (6–7 months). BB, benefiting from higher rainfall, experiences a much shorter propagation time (2–3 months). This study concludes since TWSA is the dominant contributor in drought manifestations for UGB and YCB, their rapid decline has plunged the basin into long term droughts.

Face-wise pressure variation on regular square-shaped (SQ) and two different types of setback high-rise building modes have been focused on in this study. Two building models are considered as single-side single setback (SB1) and single-side double setback (SB2). This study showcased the pressure contour envelope, which presented the maximum to minimum range of pressure variation for the 0°–180° range of attacking wind angles. According to this, the designers and researchers can use it to estimate pressure variation for any attacking wind angle. Computational fluid dynamics (CFD) and artificial neural networks (ANNs) have been employed to analyze the data sets. The 70% training data considered from CFD data can efficiently plot the pressure contour envelop. The SB2 model efficiently tries to downplay a 12%–14% average velocity. The outcome of this study indicates that the SB2 model skillfully reduces the wind speed over the building, as well as the setback distance and setback number. • The designers and researchers can easily predict the pressure coefficient range on a particular face of the setback building without analysis of individual wind angles. • A single contour can represent the pressure coefficient for any wind incidence angles. • Artificial intelligence is used to predict the pressure contour, which minimizes the effort and cost of a wind tunnel study. • The single-sided double setback building model minimizes the aerodynamic effects on different faces. • Setback distance and setback number reduce the wind speed over the building.

Nickel-metallaphotoredox catalysis has emerged as a groundbreaking approach in organic synthesis research over the last decade. It integrates the accessibility of the redox states of inexpensive, earth-abundant nickel to capture carbon-centred radicals with the ability of photoredox catalysts (PCs) to mediate single-electron transfer (SET) or energy transfer (ET) for efficient, selective, and sustainable transformations. Advances in catalyst design, reaction optimization, and mechanistic understanding have unlocked a wide range of cross-coupling protocols, enabling previously inaccessible or less efficient C-C bond formations. This progress opens new possibilities for innovative applications in pharmaceuticals, materials science, and beyond. This mini-review focuses on advancements in the last three years in the formation of challenging C(sp3)-C(sp3) and C(sp3)-C(sp2) bonds, both in two-component and three-component systems, featuring a broad substrate scope, with chemo-, regio-, and stereo- selectivity under mild conditions. Although mechanistic studies have been conducted for some systems, and kinetic isotope effects have been probed for others, detailed investigations using computational methods to understand the molecular interactions are lacking or sometimes fail to indicate a general trend of the catalytic mechanism. The discovery of novel approaches to open-shell radical species, which dictate reactivity and selectivity, will be of utmost importance in developing new reactions. These advances will enrich all areas of chemical sciences and create numerous opportunities for interdisciplinary research.