Nanopyramid Structures with Light Harvesting and Self- Cleaning Properties for Solar Cells

In this chapter, inverted and upright nanopyramid structures with light-harvesting properties and self-cleaning hydrophobic surfaces suitable for solar cells are presented. Periodic nanopyramid structures with 400–700 nm features were fabricated using interference lithography and combined dry and wet etching processes. The inverted nanopyramids (INP) were applied at the front side of the solar cells using UV nanoimprint lithography. These structures provided effective light-trapping properties and led to oblique angle light scattering and a significant reduction in reflectance resulting in higher power conversion efficiency. The second type, the periodic upright nanopyramid (UNP) structures were applied on a glass substrate by UV nanoimprint process. The glass cover is also utilized as a protective encapsulant front layer. The use of the upright nanopyramid structured cover glass in the encapsulated solar cell has also enhanced the power conversion efficiency due to the antireflection and strong light-scattering properties compared to the bare cover glass. In addition, the upright nanopyramid structured cover glass exhibited excellent self-cleaning of dust particles by rolling down water droplets. These results suggest that the nanopyramid structures with light-harvesting and self-cleaning properties can improve the performance of different types of solar cells, including thin films and glass-based PVs

Fabrication and Replication of Periodic Nanopyramid Structures by Laser Interference Lithography and UV Nanoimprint Lithography for Solar Cells Applications

In this chapter, the fabrication and replication of periodic nanopyramid structures suitable for antireflection and self-cleaning surfaces are presented. Laser interference lithography (LIL), dry etching, wet etching, and UV nanoimprint lithography (UV-NIL) are employed for the fabrication and replication of periodic nanopyramid structures. Inverted nanopyramid structures were fabricated on Si substrates by LIL and subsequent pattern transfer process using reactive ion etching, followed by potassium hydroxide (KOH) wet etching. The fabricated periodic inverted nanopyramid structures were utilized as a master mold for the nanoimprint process. The upright nanopyramid structures were patterned on the OrmoStamp-coated glass substrate with high fidelity in the first nanoimprint process. In the second nanoimprint process, inverted nanopyramid structures were replicated on the OrmoStamp-coated substrate using the fabricated upright nanopyramid glass substrate as a mold. The replicated inverted nanopyramid structure on resist-coated substrate was faithfully resolved with the high accuracy compared to original Si master mold down to nanometer scale. Both upright and inverted nanopyramid structures can be utilized as surface coatings for light trapping and self-cleaning applications for different types of solar cell and glass surfaces

A review of the water desalination systems integrated with renewable energy

Water and energy are indispensable entities for any flourishing life and civilization. The water and energy scarcities have emerged due to the dramatic growth in the population, standards of living, and the rapid development of the agricultural and industrial sectors. Desalination seems to be one of the most promising solutions to the water problem; however, it is an intensive energy process. The integration of the renewable energy into water desalination systems has become increasingly attractive due to the growing demand for the water and energy, and the reduction of the contributions to the carbon footprint. The intensive investigations on the conventional desalination systems, especially in the oil-rich countries have somewhat overshadowed the progress and implementation of the renewable energy desalination (RED) systems. The economic performance evaluation of the RED systems and its comparison with conventional systems is not conclusive due to many varying factors related to the level of technology, the source of energy availability, and the government subsidy. The small RED plants have a high capital cost, low efficiency and productivity which make RED systems uncompetitive with the conventional ones. However, the selection of the small RED plants for the remote arid areas with small water demands is viable due to the elimination of the high cost of the water transportation, and the connection to the electricity grid. The purpose of this paper is to review the technology, energy, and cost of the recent available desalination systems and their potential to be integrated with the renewable energy resources. This review suggests that the solar still distillation (SD) system, which is simply a natural evaporation-condensation process, is the most practical renewable desalination technique to be used in the remote arid areas; however, a further research is required to enhance their performance and to increase the productivities of these systems

Teaching integrated circuit and semiconductor device design in New Zealand: the University of Canterbury approach

Teaching the practical aspects of device and chip design in New Zealand presents many problems, including high manufacturing costs, long lead times, and the lack of local industry strength. Nonetheless, it is possible to overcome these issues. This paper describes the courses in these areas at the University of Canterbury, including a practical IC design project that has been running successfully for the past four years. The IC design project takes final year students through a full custom design using modern design tools and fabrication processes. The design is quite straightforward — a 4-bit arithmetic logic unit — but it emphasises the importance of design, simulation and testing. The final circuits contain a few hundred transistors, so good practice is essential. Twelve designs are integrated on to a single chip to keep costs down, and individual designs are addressed via multiplexers. The designs are fabricated using a 0.5 micron process, accessed through a multi-project vendor (MOSIS). Getting chips back from a manufacturer is significantly more motivating for the students than just performing a paper design

Performance enhancement of solar still desalination systems using revolving tubes: CFD simulation and experimental investigation

Water and energy are indispensable resources for life and civilisation. The scarcity of both water and energy have emerged as amongst the most serious concerns of our time due to the dramatic growth in population, enhancement in our standards of living, and the rapid development of the agricultural and industrial sectors in many countries. Desalination seems to be one of the most promising solutions to solve the problem of water scarcity; however, it is not without costs, as the desalination process is energy-intensive. Conventional sources of energy, such as fossil fuels, are limited, depleted and pollute the environment. Therefore, the use of renewable sources of energy such as solar energy is essential and represents a better option. Solar desalination systems are environmentally friendly and offer a win-win solution to solve shortages of both water and energy. The simplest and the most straightforward solar desalination process is the natural evaporation-condensation process of the Solar Still Desalination (SD) system. An SD system simply consists of a water basin and a tilted transparent cover that is exposed to solar radiation. SD systems have a low capital cost; however, the low productivity of these systems make the cost of the water that they produce higher than that produced via other traditional desalination systems. On balance, the selection of SD systems for remote areas that have relatively low demand for water makes those systems a feasible option, due to the elimination of the high costs of water transfer if such systems are deployed locally. SD systems can work powered by solar energy, which makes them environmentally friendly and suitable for areas that have no access to electricity, such as remote villages and less developed regions of the world. The main purpose of this study is to find a method to increase the productivity of SD systems to provide people in remote and less developed regions of the world with freshwater. The proposed technique is a simple amendment to the regular double-sloped SD system. The suggested modification was to add three parallel and symmetrical PVC tubes into the water basin of the SD system to be rotated by small DC motors. These tubes were wrapped in an absorbent black mat and were placed horizontally along the basin to be semi immersed in the water. The purpose of this modification is to stir the water in the basin and to generate a thin water layer around the tubes’ circumference, which leads to an increase in the surface area for water evaporation. This modification enhanced the water evaporation rate within the SD system, and thereby increased the productivity of this system. In this study, two SD systems: the Normal SD (NSD) system and the Modified SD (MSD) system were designed and manufactured, simulated numerically and tested experimentally. The CFD simulation was done using ANSYS-Fluent software. The experimental investigations were carried out during spring and summer in Toowoomba, Australia. The effective operation and design parameters such as water depth, the tubes’ diameter and the tubes’ rotation speed were analysed and optimised using the sensitivity analysis. The dimensional analysis, uncertainty analysis, and the cost analysis for the present experimental setup of both the SD systems were conducted as well. The daily productivity of the SD systems is equal to the distillate yield within a day and the daily efficiency is equal to this productivity divided by the daily insolation. The results show that the daily productivity and the daily efficiency of the MSD system were always higher than that of the NSD system. According to the experimental results, the maximum daily productivity and the maximum daily efficiency of the MSD system were 2.90

Influence of FK209 Cobalt Doped Electron Transport Layer in Cesium Based Perovskite Solar Cells

The efficiency and stability of perovskite solar cells (PSCs) depend not only on the perovskite film quality, but they are also influenced by the charge carriers of both the electron and hole transport layers (ETL and HTL). Doping of the carrier transport layers is considered one of effective technique applied to enhance the efficiency and performance of the PSCs. FK209 cobalt TFSI and lithium TFSI salt were investigated as dopants for mesoporous TiO2 (M-TiO2) in the ETL. Herein, FK209 cobalt doping offers improved conductivity, reproducibility and stability compared to other doping or undoped M-TiO2 control device. It has been found that an optimum concentration of 2.5 mg FK209 cobalt in the M-TiO2 has resulted in an efficiency of 15.6% on 0.36 cm2 active device area, whereas, the undoped M-TiO2 yielded an average efficiency of 10.8%. The enhanced efficiency is due to the improved conductivity of the ETL while maintaining high transparency and low surface roughness with FK209 doping. The M-TiO2 doped with FK209 has a transparency of the 90% over the visible range and its measured energy gap was 3.59 eV. Perovskite films deposited on the M-TiO2 doped with FK209 has also a lower PL intensity indicating faster charge extraction. The measured lifetime of the perovskite films deposited on the optimised M-TiO2 film was 115.8 ns

Microdevice-based mechanical compression on living cells

Compressive stress enables the investigation of a range of cellular processes in which forces play an important role, such as cell growth, differentiation, migration, and invasion. Such solid stress can be introduced externally to study cell response and to mechanically induce changes in cell morphology and behavior by static or dynamic compression. Microfluidics is a useful tool for this, allowing one to mimic in vivo microenvironments in on-chip culture systems where force application can be controlled spatially and temporally. Here, we review the mechanical compression applications on cells with a broad focus on studies using microtechnologies and microdevices to apply cell compression, in comparison to off-chip bulk systems. Due to their unique features, microfluidic systems developed to apply compressive forces on single cells, in 2D and 3D culture models, and compression in cancer microenvironments are emphasized. Research efforts in this field can help the development of mechanoceuticals in the future

Cellular transfer and AFM imaging of cancer cells using Bioimprint

A technique for permanently capturing a replica impression of biological cells has been developed to facilitate analysis using nanometer resolution imaging tools, namely the atomic force microscope (AFM). The method, termed Bioimprint™, creates a permanent cell 'footprint' in a non-biohazardous Poly (dimethylsiloxane) (PDMS) polymer composite. The transfer of nanometer scale biological information is presented as an alternative imaging technique at a resolution beyond that of optical microscopy. By transferring cell topology into a rigid medium more suited for AFM imaging, many of the limitations associated with scanning of biological specimens can be overcome. Potential for this technique is demonstrated by analyzing Bioimprint™ replicas created from human endometrial cancer cells. The high resolution transfer of this process is further detailed by imaging membrane morphological structures consistent with exocytosis. The integration of soft lithography to replicate biological materials presents an enhanced method for the study of biological systems at the nanoscale