Quantum Dots for Clean Energy Technology

Solar cells are in focus for decades due to their capability to convert solar energy into electrical energy. Quantum dots sensitized solar cell (QDSC), in which the photovoltaic (PV) effect occurs at the interface between a quantum dot (QD) conjugated wide band gap metal oxide semiconductor (MOS) and a redox electrolyte, gained much consideration due to their relatively simpler device structure and similarity to dye sensitized solar cell (DSSC), in which dye molecules replace QDs. The QDs are potentially having larger absorption cross-section, tuneable band edges, and atomic-like energy levels. These salient features make QDs capable of delivering more than one electron per single absorbed photon of sufficient energy, a phenomenon known as multi-exciton generation (MEG). The MEG effect makes QDSCs capable of achieving PV conversion efficiency (PCE) as high as 60% theoretically. Despite the remarkable feature of QDs as a light absorber, QDSCs deliver much inferior practical PCE (~8.6 %). Besides, they show inferior PCE compared to DSSCs (~13%). Therefore, this doctoral research aims to establish the structure-property correlation in QDSCs. A combination of experimental results and quantum chemical calculations under the framework of density functional theory (DFT) was employed for this purpose. In this approach, firstly CdSe QDs were synthesized using chemical methods and studied their structure and properties. Secondly realistic cluster models were empirically developed using DFT and experimental results. The structure-property correlation was established by comparing the experimental and theoretical results. The calculated absorption cross-section, band edges, band gaps, and emitting states of QDs with and without surface ligands were compared with that of RuL2(NCS)2.2H2O; L = 2,2’–bipyridyl-4,4’-dicarboxylic acid (N3) dye to correlate the capability of light absorption of QDs or dye molecules on the overall performance of device. This procedure was adopted to (i) understand the fundamental differences of electronic states in the bare QDs and the dye structures and (ii) evaluate electron channelling in QDs-ligand conjugate thus correlating with electron injection efficiency from QDs to MOS. Five parameters were concluded to have distinct effects on the PV properties of QDSCs. They are (i) emitting states of QDs, (ii) ligand usage, (iii) QDs size distribution, (iv) absorption cross-section, and (v) redox potential of electrolyte. The QDs–MOS conjugates were chemically developed and spectroscopically demonstrated efficient electron injection from QDs to MOS. However, such structures raised serious concerns on long term stability under operating conditions. This thesis finally propose future possible methodologies for stable and efficient QDSCs

Various Impact Resistance Capabilities of Tapioca Starch Based Shear Thickening Fluid (STF)

STF is a non-Newtonian flow behaviour often observed in concentrated colloidal dispersions characterized by significant, sometimes discontinuous increase in viscosity with increasing shear stress. Examples are concentrated particle colloidal suspensions such as photographic dies, paints, coatings and lubricants. When such fluid is subjected to a high-enough shear stress, it can lead to a rapid, sometimes discontinuous, increase in viscosity. The change in viscosity is due to the change of molecular arrangement structure in the colloidal suspension which usually will change from disordered liquid to ordered liquid crystals. Triangle Ternary Phase Diagram can be classified as a diagram that represents the equilibrium between the various liquid crystal (LC) phases that are formed between three components

Study of ZnO Nanospheres Fabricated via Thermal Evaporation for Solar Cell Application

A solar cell is a device that absorbs light energy to generate electrical energy. A typical example of a solar cell is the quantum dot solar cell (QDSC), which consists of three main components: (i) fluorophore: the component that absorbs light and generates excited state electrons and holes, (ii) photoelectrode: the component that transports the excited state electron and prevents recombination of excited state electrons and holes, and (iii) electrolyte: the component that re-plenishes the vacancy left by the excited electron in the hole. Despite the increasing number of research in the QDSC field, to date, a device with significant photovoltaic efficiency has not been developed. In this study, the mechanism of electron transport in a zinc oxide (ZnO) photoelectrode was investigated. Two ZnO layers were fabricated using thermal evaporation method at different vacuum pressures (5 × 10-4 and 5 × 10-5 Torr). Two solar cells were fabricated using ZnO as photoelectrode, lead sulphide as fluorophore, and a mixture of carboxymethyl cellulose and polyvinyl alcohol as electrolyte. The cell which utilized the ZnO fabricated under 5 × 10-5 Torr showed the highest efficiency ( = 0.98%), with fill factor = 22.07%, short circuit current = 2.85 mA/m2, and open circuit voltage = 80.719 mV

Mathematical Modelling for Predicting the Performance of Photovoltaic Modul

The demand for photovoltaic (PV) system is growing rapidly driven by technological development and awareness of green environment. A photovoltaic system converts the energy of light into electricity without emission of harmful by-product. A complete PV system consists of a solar panel (which combination of few solar cells), Pulse Width Modular (PWM) and a battery. Eight photovoltaic parameters are used to characterized the quality and efficiency of a PV module i.e (i) short circuit current (ISC), (ii) open circuit voltage (VOC), (iii) Theoretical Power (PT), (iv) maximum power (PMAX), (v) voltage at PMAX (VMPP) , (vi) current at PMAX (IMPP), (vii) fill factor (FF) and (viii) efficiency (). The PV parameters of laboratory scale solar cell could be determined based on current-voltage (I-V) and power-voltage (P-V) curves which could be plotted using a combination of solar simulator and a potentiostat instruments. Two additional PV parameters i.e (i) reverse saturation current of diode (IRC) and (ii) photocurrent (IPV) have been studied intensively as input of mathematical models to simulate and determine the quality and efficiency of solar cells. However, reproduceable results and robust mathematical models are yet to be established. A mathematical model employing the IRC, IPV and diode ideality factor (a) – which received lack of focus by previous researchers; is proposed. We have validated the mathematical model by comparing the calculation I-V and P-V curves results with the specifications established by the manufacturer. We have conducted three studies based on different specification of silicon based solar module i.e (i) 300W, (ii) 265W and (iii) 250W to obtain temperature distributions and average solar irradiance at selected locations. Through a comparative analysis, the theoretical calculation results and the manufacturers’ specifications are in good agreement

Agarwood (gaharu) research rekindled interest, stirs debate at the 40th International Symposium on Essential Oils

Savigliano, Italy Sept 7-9. The MOSTI-funded research (Science Fund 02-0l-16-SF0005) headed by Prof Mashitah Mohd Yusoff rekindled tremendous interest and debate when presented by lead researcher and FIST's lecturer, Saiful Nizam Tajuddin

Mathematical modelling for predicting the performance of photovoltaic module

The demand for photovoltaic (PV) system is growing rapidly driven by technological development and awareness of green environment. A photovoltaic system converts the energy of light into electricity without emission of harmful by-product. A complete PV system consists of a solar panel (which combination of few solar cells), Pulse Width Modular (PWM) and a battery. Eight photovoltaic parameters are used to characterized the quality and efficiency of a PV module i.e (i) short circuit current (ISC), (ii) open circuit voltage (VOC), (iii) Theoretical Power (PT), (iv) maximum power (PMAX), (v) voltage at PMAX (VMPP) , (vi) current at PMAX (IMPP), (vii) fill factor (FF) and (viii) efficiency (). The PV parameters of laboratory scale solar cell could be determined based on current-voltage (I-V) and power voltage (P-V) curves which could be plotted using a combination of solar simulator and a potentiostat instruments. Two additional PV parameters i.e (i) reverse saturation current of diode (IRC) and (ii) photocurrent (IPV) have been studied intensively as input of mathematical models to simulate and determine the quality and efficiency of solar cells. However, reproduceable results and robust mathematical models are yet to be established. A mathematical model employing the IRC, IPV and diode ideality factor (a) – which received lack of focus by previous researchers; is proposed. We have validated the mathematical model by comparing the calculation I-V and P-V curves results with the specifications established by the manufacturer. We have conducted three studies based on different specification of silicon based solar module i.e (i) 300W, (ii) 265W and (iii) 250W to obtain temperature distributions and average solar irradiance at selected locations. Through a comparative analysis, the theoretical calculation results and the manufacturers’ specifications are in good agreemen

Spotlight on faculty member: Dr. Natanamurugaraj Govindan, marine bologist

Dr. Natanamurugaraj Govindan was born in August 1, 1979 at Pudukkottai district, Tamil Nadu State, India, where his parents and sister continue to play a big part in his life and career. He received his B.Sc. and M.Sc. degrees in Botany from Bharathidasan University, Trichyrappalli and B.Ed. degree in Biological Science from Alagappa University, Ka raikudi, India. Following his Ph.D specialization in Marine Algal Biotechnology from Bharathidasan University, India, Dr. Natanam was appointed Post-Doctoral Research fellow in the School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand. He has written a book entitled "Marine diatoms from Ka raikal coastal region (India)': This book describes taxonomy and identification of marine microalgae (particularly diatoms) for biotechnology students

A Study on Dielectric Properties of The Cellulose Derivative-NH4Br-Glycerol- Based The Solid Polymer Electrolyte System

The characterization of biopolymer-based solid polymer electrolytes (SPEs) has been carried out in this present work. Cellulose derivative was chosen due to its superior physical attributes. In this work, NH4Br-doped glycerol plasticized carboxyl methylcellulose-based SPEs were successfully prepared via the solution casting method. The conductivity and dielectric properties of the prepared films were investigated using the impedance analysis which presented ~1.91×10-3 Scm-1 (with addition of 6 wt% of glycerol). In addition, the studied SPE system shows a non-Debye behaviour without asingle relaxation time. The findings of the research indicate that the complexes of NH4Br and glycerol in the cellulose derivative influence the ionic conductivity and dielectric properties of the SPE system

Job Opportunities in Material(s) Technology

Materials are substances of universe which have properties that make them useful in structures, machines, devices, products, and systems. There are three closely connected areas of study related to materials, namely material(s) technology, materials engineering and materials science. Material(s) technology is a relatively comprehensive discipline that begins with the production of goods from raw materials to processing of materials into the shapes and forms needed for specific applications. Material(s) technologists work with materials such as metals, plastics, rubbers and ceramics. They study how the composition, structure, processing, and application of these materials, are inter-related

Characterizations of MoS2 nanosphere fabricated using vacuum thermal evaporation at steady and rapid heating

Two-dimensional MoS2 has been speculated to be the best material to replace graphene due to its peculiar structural-electronic properties. The MoS2 with size smaller than its exciton Bohr radius (ca. 1.61 nm) would favor multi exciton generation upon absorption of photon with sufficient energy, Ephoton ≫ Egap (1.89 eV); which would increase the efficiency of an excitonic solar cell greater than 60%. Despite promising properties of the MoS2, however an excitonic solar cell with high efficiency is yet to be exhibited. In this work, the MoS2 thin films were fabricated using vacuum thermal evaporation technique and characterized. Four objectives have been outlined i.e., to study the effect of heating rate (steady, and rapid) on the (i) morphology, (ii) size, (iii) optoelectronic and (iv) crystal properties of the fabricated thin films. The MoS2 precursor was heated at the rate 2.027 A/s (steady), and 18.75 A/s (rapid), 1.5 × 10−3 Torr, 1.48 A, and 4.58 V. The deposited films later were characterized using Field Emission Scanning Electron Microscope with Energy Dispersive X-ray attachment, photoluminescence spectrometer, UV–vis-NIR spectrometer, and X-ray Diffractometer. The fabricated thin films exhibited nanosphere morphology with different size distributions i.e., wide (steady heating), and narrow (rapid heating). Two hypotheses were made based on the optoelectronic properties i.e., the basic building block of the MoS2 thin film fabricated under steady heating is (i) experiencing stronger quantum confinement effect, and (ii) dominated by nanocrystals which are smaller than that of the rapid heating. Similar energy loss could be expected in both MoS2 thin films i.e., ca. 0.15 to 0.17 eV, indicating the existence of shallow trap states. The MoS2 thin films were dominated by (0 0 2), (0 0 4), and (1 0 6) crystal planes. Therefore, the vacuum thermal evaporation technique would offer materials with unique size, crystal arrangement, and optoelectronic properties upon change of heating rate