Electrochemical study of zinc selenide thin films prepared for photovoltaic applications

Polycrystalline thin films of cubic zinc selenide semiconductor have been electrochemically deposited on conducting substrates of indium tin oxide, ITO glass. Initial investigation with voltammetry was done and the influence of deposition potential and of bath temperature on the films crystallinity is discussed. At room temperature, amorphous films were obtained and at elevated bath temperatures between 55 oC and 75 oC, films were crystallined. The best deposition voltage obtained was -0.95 V vs. Ag /AgCl while at lower deposition potentials, the films do not form well. Energy Dispersive Analysis and X-Ray spectrum indicate that the films deposited at 65 oC and -0.95 V vs. Ag/AgCl have nearly stoichiometric Zn: Se ratio. Energy band gap and refractive index are in agreement with reported results

Fabrication, Characterization, and Optimization of CdS and CdSe Quantum Dot-Sensitized Solar Cells with Quantum Dots Prepared by Successive Ionic Layer Adsorption and Reaction

CdS and CdSe quantum dot-sensitized solar cells (QDSSCs) were used for the study of determining the optimum preparation parameters that could yield the best solar cell performance. The quantum dots (QDs) were coated on the surface of mesoporous TiO2 layer deposited on FTO substrate using the successive ionic layer adsorption and reaction (SILAR) method. In this method the QDs are allowed to grow on TiO2 by dipping the TiO2 electrode successively in two different solutions for predetermined times. This method allows the fabrication of QDs in a facile way. Three preparation parameters that control the QD fabrication were investigated: concentration of precursor solutions, number of dipping cycles (SILAR cycles), and dipping time in each solution. CdS based QDSSC showed optimum performance when the QDs were prepared from precursor solutions having the concentration of 0.10 M using 4 dipping cycles with the dipping time of 5 minutes in each solution. For CdSe QDSSC, the optimum performance was achieved with QDs prepared from 0.03 M precursor solutions using 7 dipping cycles with 30 s dipping time in each solution. The QDs deposited on TiO2 surface were characterized using UV-vis absorption spectroscopy, FESEM, and TEM imaging

A Suitable Polysulfide Electrolyte for CdSe Quantum Dot-Sensitized Solar Cells

A polysulfide liquid electrolyte is developed for the application in CdSe quantum dot-sensitized solar cells (QDSSCs). A solvent consisting of ethanol and water in the ratio of 8 : 2 by volume has been found as the optimum solvent for preparing the liquid electrolytes. This solvent ratio appears to give higher cell efficiency compared to pure ethanol or water as a solvent. Na2S and S give rise to a good redox couple in the electrolyte for QDSSC operation, and the optimum concentrations required are 0.5 M and 0.1 M, respectively. Addition of guanidine thiocyanate (GuSCN) to the electrolyte further enhances the performance. The QDSSC with CdSe sensitized electrode prepared using 7 cycles of successive ionic layer adsorption and reaction (SILAR) produces an efficiency of 1.41% with a fill factor of 44% on using a polysulfide electrolyte of 0.5 M Na2S, 0.1 M S, and 0.05 M GuSCN in ethanol/water (8 : 2 by volume) under the illumination of 100 mW/cm2 white light. Inclusion of small amount of TiO2 nanoparticles into the electrolyte helps to stabilize the polysulfide electrolyte and thereby improve the stability of the CdSe QDSSC. The CdSe QDs are also found to be stable in the optimized polysulfide liquid electrolyte

Causative failure factors of communications management in mixed-use development projects in Malaysia

Construction delay has been a persistent challenge for the Malaysian construction industry. This has resulted in many issues, including public complaints, government loss of reputation and income and a decline in the gross domestic product output of the industry. Furthermore, the construction industry is a complex business with several stakeholders continually sharing information. Hence, ensuring project success has to be the utmost important task of a project manager. Often the construction industry is marred by high cases of delays, overruns, poor quality, health and safety issues, emissions and sustainability issues as a result of ineffective communication practices. Therefore, this paper aims to examine causative failure factors of communications management in mixed-use development projects in Malaysia. Based on the literature review, 11 factors and 44 items were identified. These factors and items were evaluated by 141 respondents from the Malaysian construction industry. Data analysis was done using SPSS 23.0. This study found that the most critical causative failure factor is team meeting discussions. The respondents believe that there is lack of stakeholder cooperation due to poor representation during the discussions, which also reflects the inadequacy of mutual respect, confidence and trust among stakeholders. As a recommendation, frequent team meeting discussions provide a platform for effective information exchange, thus help to reduce mixed-use project failures in Malaysia

Contractor's performance appraisal system in the Malaysian construction industry: Current practice, perception and understanding

Performance appraisal system is a common practice in any organisation to appraise performance of workers. In the Malaysian construction industry, performance appraisal system is applied to appraise contractor's performance in many angles including: quality performance; time performance; cost performance; environmental performance; health and safety performance; productivity performance; and human resources performance. This is where the Construction Industry Development Board (CIDB) established three guidelines in strengthening the Construction Industry Transformation Programme (CITP) by appraising the contractor's performance through identification of their weaknesses as well as drafting and offering suitable trainings in enhancing their performance. This paper is therefore undertaken with the objectives of: (1) determining the current practice of contractor's performance appraisal system in the Malaysian construction industry; and (2) examining the construction players' perception and understanding on the existing contractor's performance appraisal system in the Malaysian construction industry. A set of questionnaires is designed and distributed to 157 contractors from G1 to G7 class. The paper finds that: (1) contractor's performance appraisal system is benefiting the contractors yet should be improved for its efficiency; and (2) construction players have sufficient understanding on contractor's performance appraisal system. It is expected that the improvement of contractor's performance appraisal system via the findings of this paper would assist in achieving the three focuses of Transformasi Nasional 2050 (TN50), namely science and technology, urban prosperity as well as environment

Phthaloylchitosan-Based Gel Polymer Electrolytes for Efficient Dye-Sensitized Solar Cells

Phthaloylchitosan-based gel polymer electrolytes were prepared with tetrapropylammonium iodide, Pr 4 NI, as the salt and optimized for conductivity. The electrolyte with the composition of 15.7 wt.% phthaloylchitosan, 31.7 wt.% ethylene carbonate (EC), 3.17wt.% propylene carbonate (PC), 19.0 wt.% of Pr 4 NI, and 1.9wt.% iodine exhibits the highest room temperature ionic conductivity of 5.27 x 10 -3 S cm -1. The dye-sensitized solar cell (DSSC) fabricated with this electrolyte exhibits an efficiency of 3.5% with.. SC of 7.38mAcm -2,.. OC of 0.72V, and fill factor of 0.66. When various amounts of lithium iodide (LiI) were added to the optimized gel electrolyte, the overall conductivity is observed to decrease. However, the efficiency of the DSSC increases to a maximum value of 3.71% when salt ratio of Pr 4 NI : LiI is 2 : 1. This cell has.. SC,.. OC and fill factor of 7.25mAcm -2, 0.77V and 0.67, respectively

Analytical study of a cylindrical linear electromagnetic pulsing motor for electric vehicles

The cylindrical linear electromagnetic pulsing motor (EMPM) is an alternative electric vehicle (EV) to be simulated in this study. The proposed design on the cylindrical linear EMPM will replace the piston engine in an internal combustion engine (ICE) which produces linear motion. It can eliminate problems related to internal combustion engines (ICE) such as engine weight and friction where fewer components have been used. In this paper, an analytical model was constructed and predicted the magnetic equivalent circuit (MEC) that can solve with the same technique as the electrical circuit. The initial magneto-statics analysis was conducted through the finite element magnetic software (FEMs) for magnetic filed problem so that the magnetic flux relationship could be predicted. Furthermore, the FE modelling and analysis is followed by a MATLAB/Simulink software calculation to predict the cylinder linear EMPM. Finally, the simulation results of the FE models regarding plunger force, thrust, plunger distance, speed, and power motor were presented and compared with the regulated counterparts obtained from the experimental setup

Utilization of saffron (Crocus sativus L.) as sensitizer in dye-sensitized solar cells (DSSCs)

Photoelectrodes of dye-sensitized solar cells (DSSCs) have been prepared using nanosized titanium dioxide that have soaked in a solution of different saffron (Crocus sativus L.) spice content in ethanol. The optimized polyacrylonitrile (PAN)-based gel polymer electrolyte with 40.93 wt.% ethylene carbonate, 37.97 wt.% propylene carbonate, 4.37 wt.% tetrapropylammonium iodide, 9.86 wt.% PAN, 1.24 wt.% 1-butyl-3-methylimidazolium iodide, 4.35 wt.% lithium iodide and 1.28 wt.% iodine has been used as the electrolyte for DSSC. The electrolyte has conductivity of 2.91 mS cm−1 at room temperature (298 K). DSSCs were also sensitized with saffron solution that has been added with 30 wt.% chenodeoxycholic acid (CDCA) co-adsorbent and designated as DSSC P4. The solar cell converts light-to-electricity at an efficiency of 0.31%. This is 29% enhancement in efficiency for the DSSC without addition of CDCA in the saffron-ethanol solution. The DSSC exhibits current density at short-circuit (J sc ) of 1.26 mA cm−2, voltage at open circuit (V oc ) of 0.48 V and 51% fill factor. DSSC P4 also exhibits the highest incident photon-to-current density of more than 40% at 340 nm wavelength

Impact of tetrabutylammonium, iodide and triiodide ions conductivity in polyacrylonitrile based electrolyte on DSSC performance

Gel polymer electrolytes (GPEs) with polyacrylonitrile (PAN)-based polymer, ethylene carbonate (EC) and propylene carbonate (PC) plasticizers, and different amounts of tetrabutylammonium iodide (TBAI) salt and iodine (I2) have been prepared and used in dye-sensitized solar cells (DSSCs). The maximum room temperature conductivity of 5.14 mS cm−1 is obtained for electrolyte with a composition of 8 wt% PAN-30 wt% EC-30 wt% PC-30 wt% TBAI-2 wt% I2 (S3 electrolyte) which influenced by the highest charge carrier density of 7.93 × 1020 cm−3 estimated from fitting the impedance Nyquist plot. The DSSC fabricated with S3 electrolyte revealed the highest power conversion efficiency of 3.45% with open-circuit voltage (Voc) of 582 mV and short-circuit current density (Jsc) of 12.9 mA cm−2. The incident photon-to-current conversion efficiency of the DSSC with highest efficiency is 54.01%. The electrical impedance spectroscopy of the same cell shows the lowest series resistance indicating the superiority of electrolyte charge transport characteristics in DSSC. In addition, electron transfer time constant and electron recombination time , charge collection efficiency , electron diffusion coefficient and diffusion length of DSSC fabricated with GPEs prepared have been estimated by intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy techniques. The DSSC with highest efficiency shows lowest of 34.46 ms and highest of 90.41 ms due to the huge amount of TBA+ ions that covered the surface area of mesoporous TiO2. The of 0.62, D of 4.00 × 10−5 cm2 s−1 and of 19.02 μm further support the photovoltaic efficiency of DSSC