Engineering of binary metal oxide nanostructures for highly efficient and stable excitonic solar cells

Ph.DDOCTOR OF PHILOSOPH

Perovskite solar cells: progress and advancements

Organic–inorganic hybrid perovskite solar cells (PSCs) have emerged as a new class of optoelectronic semiconductors that revolutionized the photovoltaic research in the recent years. The perovskite solar cells present numerous advantages include unique electronic structure, bandgap tunability, superior charge transport properties, facile processing, and low cost. Perovskite solar cells have demonstrated unprecedented progress in efficiency and its architecture evolved over the period of the last 5–6 years, achieving a high power conversion efficiency of about 22% in 2016, serving as a promising candidate with the potential to replace the existing commercial PV technologies. This review discusses the progress of perovskite solar cells focusing on aspects such as superior electronic properties and unique features of halide perovskite materials compared to that of conventional light absorbing semiconductors. The review also presents a brief overview of device architectures, fabrication methods, and interface engineering of perovskite solar cells. The last part of the review elaborates on the major challenges such as hysteresis and stability issues in perovskite solar cells that serve as a bottleneck for successful commercialization of this promising PV technology

Metal oxide semiconducting interfacial layers for photovoltaic and photocatalytic applications

The present review rationalizes the significance of the metal oxide semiconductor (MOS) interfaces in the field of photovoltaics and photocatalysis. This perspective considers the role of interface science in energy harvesting using organic photovoltaics (OPVs) and dye-sensitized solar cells (DSSCs). These interfaces include large surface area junctions between photoelectrodes and dyes, the interlayer grain boundaries within the photoanodes, and the interfaces between photoactive layers and the top and bottom contacts. Controlling the collection and minimizing the trapping of charge carriers at these boundaries is crucial to overall power conversion efficiency of solar cells. Similarly, MOS photocatalysts exhibit strong variations in their photocatalytic activities as a function of band structure and surface states. Here, the MOS interface plays a vital role in the generation of OH radicals, which forms the basis of the photocatalytic processes. The physical chemistry and materials science of these MOS interfaces and their influence on device performance are also discussed

Data of chemical analysis and electrical properties of SnO2-TiO2 composite nanofibers

In this data article, we provide energy dispersive X-ray spectroscopy (EDX) spectra of the electrospun composite (SnO2-TiO2) nanowires with the elemental values measured in atomic and weight%. The linear sweep voltammetry data of composite and its component nanofibers are provided. The data collected in this article is directly related to our research article “Synergistic combination of electronic and electrical properties of SnO2 and TiO2 in a single SnO2-TiO2 composite nanowire for dye-sensitized solar cells

Advances in stable and flexible perovskite solar cells

Roll-to-roll (R2R) production is an innovative approach and is fast becoming a very popular industrial method for high throughput and mass production of solar cells. Replacement of costly indium tin oxide (ITO), which conventionally has served as the transparent electrode would be a great approach for roll to roll production of flexible cost effective solar cells. Indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) are brittle and ultimately limit the device flexibility. Perovskite solar cells (PSCs) have been the centre of photovoltaic research community during the recent years owing to its exceptional performance and economical prices. The best reported PSCs fabricated by employing mesoporous TiO2 layers require elevated temperatures in the range of 400–500 °C which limits its applications to solely glass substrates. In such a scenario developing flexible PSCs technology can be considered a suitable and exciting arena from the application point of view, them being flexible, lightweight, portable, and easy to integrate over both small, large and curved surfaces

Influence of the Viscosity of Nanofluids on Surface Roughness in End Milling of Nickel Alloys with Minimum Quantity Lubrication

Minimum Quantity Lubrication (MQL) using vegetable oils is considered a sustainable lubrication method, particularly for machining difficult-to-machine materials like nickel and titanium alloys. Although a significant influence of nanofluid viscosity on lubrication has been observed in MQL machining, as evidenced by limited literature, the influence of viscosity on MQL machining of difficult-to-machine materials like nickel alloys is yet to be established. This research aimed to study the influence of viscosity on the MQL end milling machining performance of Inconel 718 alloy. Three representative nanofluids were prepared using metallic (Cu), ceramic (Al2O3), and non-metallic (CNT) nanoparticles and palm oil. It was found that the CNT had a significant influence on viscosity at the same concentration, resulting in the highest viscosity of 433.2cP at 30oC. When the machining performance was investigated under different lubricating conditions (dry machining, flood cooling, and MQL), the viscosity of the nanofluids was observed to have a substantial influence on the machining performance. The CNT nanofluid with the highest viscosity penetrated the machining zone producing the lowest surface roughness with improved lubrication by 65.4% and 30.18% when compared with dry machining and flood cooling, respectively. The surface topography study confirmed the superior lubrication performance of CNT nanofluid. Overall, MQL milling with 0.5wt% nanoparticle concentration demonstrated effective machining performance when compared with dry machining and flood cooling

Structural Changes and Electrochemical Stability of Ionogel Incorporating Tetraethyl Orthosilicate and PVDF-HFP

Ionogels are emerging hybrid materials and are widely studied due to the combination of thermophysical properties from ionic liquid and mechanical integrity from the polymer matrix. Ionic liquid has received wide attention due to its promising properties, high ionic conductivity, and thermal stability. The liquid nature of ionic liquid has restricted its application. Thus, the confinement of ionic liquid within a polymer matrix has allowed ionogel to be applied in strain sensors and lithium-ion batteries. Nevertheless, the compatibility between the polymer matrix and ionic liquid is crucial for ionogel. Incompatibility between polymer host and ionic liquid results in low ionic conductivity, poor mechanical strength, and undesired for practical application. The interaction between polymer matrix and ionic liquid is studied in this study through optical microscopy. The addition of ionic liquid resulted in the disappearance of the polymer matrix’s highly porous nature, as evidenced by the optical microscopy images. This disappearance of the porous nature suggests the compatibility of the polymer matrix with ionogel. Furthermore, the electrochemical stability of the ionogel is also examined through linear sweep voltammetry technique and achieved 2.3V

Electrospinning research and products: The road and the way forward

Electrospinning is one of the most accessed nanofabrication techniques during the last three decades, attributed to its viability for the mass production of continuous nanofibers with superior properties from a variety of polymers and polymeric composites. Large investments from various sectors have pushed the development of electrospinning industrial setups capable of producing nanofibers in millions of kilograms per year for several practical applications. Herein, the lessons learned over three decades of research, innovations, and designs on electrospinning products are discussed in detail. The historical developments, engineering, and future opportunities of electrospun nanofibers (ESNFs) are critically addressed. The laboratory-to-industry transition gaps for electrospinning technology and ESNFs products, the potential of electrospun nanostructured materials for various applications, and academia-industry comparison are comprehensively analyzed. The current challenges and future trends regarding the use of this technology to fabricate promising nano/macro-products are critically demonstrated. We show that future research on electrospinning should focus on theoretical and technological developments to achieve better maneuverability during large-scale fiber formation, redesigning the electrospinning process around decarbonizing the materials processing to align with the sustainability agenda and the integration of electrospinning technology with the tools of intelligent manufacturing and IR 4.0

Open circuit voltage of organic solar cells: an in-depth review

Organic solar cells (OSCs) have developed progressively in efficiency over the last two decades. Though it is promising, this technology is still far from realizing its full prospect. One of the most important parameters that determine the efficiency of OSCs is the open-circuit voltage (VOC), which represents the maximum voltage a solar cell can provide to an external circuit. Light harvesting materials employed in OSCs have an optical band gap of around 1.7 to 2.1 eV and yet the VOC barely exceeds 1.0 V, which is approximately just half of the photon's original energy. By contrast, in inorganic counterparts such as Si, CIGS and GaAs, the difference is only 0.3 to 0.45 eV between the material bandgap and VOC. Hence, to achieve higher power conversion efficiencies (PCEs) in OSCs, a detailed understanding of the origins of VOC and the associated energetic loss mechanisms is indispensable. The presented review takes the opportunity to elaborate various governing mechanisms and factors affecting the VOC from a comprehensive yet insightful standpoint. This report also provides a concise synthesis of intricate interdependencies among the factors influencing VOC and highlights the potential research strategies to improve VOC, rendering possible pathways to facilitate the viable commercialization of OSCs

Metal Oxide Semiconducting Interfacial Layers for Photovoltaic and Photocatalytic Applications

The present review rationalizes the significance of the metal oxide semiconductor (MOS) interfaces in the field of photovoltaics and photocatalysis. This perspective considers the role of interface science in energy harvesting using organic photovoltaics (OPVs) and dye-sensitized solar cells (DSSCs). These interfaces include large surface area junctions between photoelectrodes and dyes, the interlayer grain boundaries within the photoanodes, and the interfaces between photoactive layers and the top and bottom contacts. Controlling the collection and minimizing the trapping of charge carriers at these boundaries is crucial to overall power conversion efficiency of solar cells. Similarly, MOS photocatalysts exhibit strong variations in their photocatalytic activities as a function of band structure and surface states. Here, the MOS interface plays a vital role in the generation of OH radicals, which forms the basis of the photocatalytic processes. The physical chemistry and materials science of these MOS interfaces and their influence on device performance are also discussed