IOP Conference Series: Materials Science and Engineering, 2020
Tin and germanium-based perovskite solar cell is gaining interest in lead-free perovskite solar c... more Tin and germanium-based perovskite solar cell is gaining interest in lead-free perovskite solar cells as it is less toxic as compared to lead but possess almost all the characteristics of a perfect solar cell materials. Within 5 years, the reported efficiency of tin-based solar cells has increased from 6.4% to 9%. Although facing with stability issues as it is easily oxidised in ambient air, several studies have proven that the stability issues can be reduced. One of it is by using cesium as the ‘A’ cation. On the other hand, although studies on germanium-based perovskite solar cells are rarely conducted, promising results are shown when it is alloyed with tin producing narrower bandgaps and better stability owing to the protection of the GeO2 surface layer.
IOP Conference Series: Materials Science and Engineering, 2019
Ag/TiO2 thin film was prepared by the sol-gel method through the hydrolysis of titanium tetraisop... more Ag/TiO2 thin film was prepared by the sol-gel method through the hydrolysis of titanium tetraisopropoxide and silver nitrate solution. Various amount of PEG was doped into the solution preparation to study the effect on crystalline state and microstructural of the prepared thin films. Spin coating method was used to get uniform film on ITO glass substrate followed by annealing process for 1 hour. The obtained thin films were analysed using XRD test, SEM and AFM. Results showed that all the prepared thin films are in anatase TiO2 Increasing the PEG amount into the solution could increase the thickness and surface roughness of the obtained thin films.
Thin-film solar cell Absorption in Si x Ge 1Àx layers Bandgap engineering Hetero-junction solar c... more Thin-film solar cell Absorption in Si x Ge 1Àx layers Bandgap engineering Hetero-junction solar cells Heteroepitaxial growth of Si x Ge 1Àx on Si a b s t r a c t Crystalline silicon (c-Si) solar cell represents a cost effective, environment-friendly, and proven renewable energy resource. Industrially manufacturing of c-Si solar has now matured in terms of efficiency and cost. Continuing cost-effective efficiency enhancement requires transition towards thinner wafers in near term and thin-films in the long term. Successful implementation of either of these alternatives must address intrinsic optical absorption limitation of Si. Bandgap engineering through integration with Si x Ge 1Àx layers offers an attractive, inexpensive option. With the help of PC1D software, role of Si x Ge 1Àx layers in conventional c-Si solar cells has been intensively investigated in both wafer and thin film configurations by varying Ge concentration, thickness, and placement. In wafer configuration, increase in Ge concentration leads to enhanced absorption through bandgap broadening with an efficiency enhancement of 8% for Ge concentrations of less than 20%. At higher Ge concentrations, despite enhanced optical absorption, efficiency is reduced due to substantial lowering of open-circuit voltage. In 5-25-lm thickness, thin-film solar cell configurations, efficiency gain in excess of 30% is achievable. Therefore, Si x Ge 1Àx based thin-film solar cells with an order of magnitude reduction in costly Si material are ideally-suited both in terms of high efficiency and cost. Recent research has demonstrated significant improvement in epitaxially grown Si x Ge 1Àx layers on nanostructured Si substrates, thereby enhancing potential of this approach for next generation of c-Si based photovoltaics.
Crystalline silicon (c-Si) solar cell dominates 90% of photovoltaic (PV) market. The c-Si is the ... more Crystalline silicon (c-Si) solar cell dominates 90% of photovoltaic (PV) market. The c-Si is the most mature of all PV technologies and expected to remain leading the PV technology by 2050. The attractive characters of Si solar cell are stability, long lasting and higher lifetime. Presently, the efficiency of c-Si solar cell is still stuck at 25% for one and half decades. Tandem approach is one of the attempts to improve the Si solar cell efficiency with higher bandgap layer is stacked on top of Si bottom cell. Perovskite offers a big potential to be inserted into a tandem solar cell. Perovskite with bandgap of 1.6 to 1.9 eV will be able to absorb high energy photons, meanwhile c-Si with bandgap of 1.124 eV will absorb low energy photons. The high carrier mobility, high carrier lifetime, highly compatible with both solution and evaporation techniques makes perovskite an eligible candidate for perovskite-Si tandem configuration. The solution of methyl ammonium lead iodide (MAPbI3) was prepared by single st...
The back-contact crystalline silicon solar cell represents an advanced configuration in which int... more The back-contact crystalline silicon solar cell represents an advanced configuration in which interdigitated positive and negative contacts are placed on the rear surface. Highest conversion efficiency, elimination of shading losses, co-planarity of cell interconnections, and uniform black appearance, represent some of the most significant features of this type of solar cell. However, the manufacturing process complexity leads to significantly higher production cost making it difficult to compete with conventional mono and poly crystalline Si-based Photovoltaics industry. Over the years, an increasing number of researchers have reported on methods and processes aimed at reduction in manufacturing cost. This review paper attempt an extensive review of several categories of back-contact silicon solar cells, relevant design innovations, specific cost advantages especially in terms of using lower lifetime materials, their efficiency advantages in terms of geometry and wafer type, and their manufacturing technologies. In addition, available simulation tools for numerical investigation on back-contact structures and advanced device concepts have also presented in order to better understand underlying physical considerations in terms of passivation, both surface and volume, and minority carrier lifetime.
In this paper, a respond surface methodology (RSM) model has been developed using three levels Bo... more In this paper, a respond surface methodology (RSM) model has been developed using three levels Box-Benkhen experimental design (BBD) technique to study the influence of several metal-assisted chemical etching (MACE) process variables on the properties of nanostructured silicon (Si) wafer. Five process variables are examined i.e. concentrations of silver (Ag), hydrofluoric acid (HF), deposition time, H2O2 concentration and etching time as a function of etching rate. Design-Expert® software (version 7.1) is used in formulating the RSM model of five factors with 46 experiments. A regression quadratic model is developed to correlate the process variables where the most significant factors are identified and validated using analysis of variance (ANOVA). The model for etching rate is found to be significant with R2 of 0.8, where both Ag concentrations and etching time are the major influence.
The porous silicon etching creates a thin layer of nanowires that enhances the absorption and red... more The porous silicon etching creates a thin layer of nanowires that enhances the absorption and reduces the reflectance of light. In this work we present porous silicon nanowires were fabricated on doublesided of n-type Si (111) wafers with 525 µm thickness using a single step metal assisted chemical etching process. Two different resistivity (Ω=50-100 cm, Ω= >3000 cm) of wafer was involved in this study with different etching time (10, 20, 30, 40 min). The properties of porous silicon structure changed with increase time of etching. The investigation of the porous silicon nanowires structure revealed that the formation of nanowires depends on the doping concentration of the wafers. We make a preliminary determination as the light trapping properties for samples with etching time 10 min for low resistivity and 20 min for high resistivity. A different mechanism of slow charge trapping was observed using Kelvin Probe measurement. We show conclusively that the charge generated at the interface charge occurs by illumination on short length of nanowires (<405nm) and low surface roughness (<35 nm) for both resistivity of the wafers.
High quality Ge and Si x Ge 1-x films grown on Si substrates are attractive for a wide range of a... more High quality Ge and Si x Ge 1-x films grown on Si substrates are attractive for a wide range of applications in optics, optoelectronics, and high efficiency solar cells. In this study, heteroepitaxial growth of Ge on nanostructured Si surfaces has been investigated. Thermally evaporated amorphous Ge films are vacuum-deposited and crystallized by thermal annealing at 1000 °C. Scanning electron microscope (SEM), spectroscopy (RS), infrared (IR) transmission, and Raman methods are used to characterize amorphous and crystalline Ge films. SEM analysis reveals presence of dominant features including cracks, microscopic roughness, and islands. RS exhibits strong multiple peaks attributed to crystalline structures related to Si-Ge at ~ 444 cm-1 and Ge at 300 cm-1 ; narrow and stronger peaks are observed in thermally annealed films. A comparison of IR transmission measurements in 900-1700-nm spectral range shows that amorphous film absorption is significantly higher than that of crystalline films consistent with respective bandgaps. A more detailed analysis including EDX and XRD measurements will be presented at the conference.
Role of micro and nanostructures in enhancing IR transmission in Si wafers has been investigated.... more Role of micro and nanostructures in enhancing IR transmission in Si wafers has been investigated. Based on feature dimensions, incident light interaction can be described in terms of: (a) geometrical optics for wavelengths significantly smaller than surface dimensions, (b) diffractive optics for wavelengths comparable to surface features, and (c) physical optics for wavelengths substantially larger than surface features. Randomly distributed features in micro and nanoscale regimes were fabricated on identical Si wafers. A simple IR optical transmission system based on InGaAs photodetector and monochromator was developed for optical measurements. Optical transmission near the bandgap was substantially reduced by randomly distributed nanostructures likely attributed to diffractive optics. At the conference, details of several structures along with their reflection and transmission measurements will be presented in order to determine optimum surfaces for lowest transmission near the bandgap.
Fenton process is one of the advanced oxidation processes (AOPs) used to remove complex organic p... more Fenton process is one of the advanced oxidation processes (AOPs) used to remove complex organic pollutants in wastewater. In this study, instead of iron sulfate (FeSO 4), nano zero valent iron (nZVI) was used as a major source of ferrous iron (Fe 2+). In order to enhance the process, ultrasound was utilized in this study. Results show that, with the aid of ultrasound, nZVI produced more Fe 2+ compared to FeSO 4 at pH 2. Furthermore, combination of higher intensity and longer sonication time in Fenton process acceleratde the chemical oxygen demand (COD) removal from palm oil mill effluent (POME). Through the process, 80% of COD content was removed within 2 hours instead of 24 hours of silent degradation.
Proceedings of the 3rd WSEAS International Conference on Energy Planning, Energy Saving, Environmental Education, EPESE
Abstract:–Meteorological data has been used in determining of global and diffuse solar radiation ... more Abstract:–Meteorological data has been used in determining of global and diffuse solar radiation for years. Various methods have been developed and proved to be accurately comparable to the measured value. Among all, the most common meteorological parameter used are cloud cover, sunshine duration hours and number of rainy days, A review of various methods used in determination of global solar radiation by using cloud cover is presented in this paper.
Abstract:-Satellite images have been indentified as an alternative and accurate method for predic... more Abstract:-Satellite images have been indentified as an alternative and accurate method for predicting average annual daily solar radiation of a specific location. These images can be use to predict the performance and sizing of various solar energy systems such as solar thermal and photovoltaic applications. The data from satellite images are used and compared with the actual readings from solar instruments. The results are then used to estimate solar intensity for other places where solar instrument is not available. Malaysia ...
The prevailing opinion among the scholars is that history as a study should determine the politic... more The prevailing opinion among the scholars is that history as a study should determine the politics of memory and serve as a model for the narratives of collective identity. However, it should be remembered that memory and history, despite their close relationship, have different goals and realize different functions in society. Historical science cannot define the collective memory, but must participate in shaping the politics of memory. The task of historical politics is precisely to cut off multiplicity in order to provide an opportunity for action, while the task of historical science as a whole is to preserve and increase the potential of multiplicity to provide a wide choice of possible actions.
IOP Conference Series: Materials Science and Engineering, 2020
Tin and germanium-based perovskite solar cell is gaining interest in lead-free perovskite solar c... more Tin and germanium-based perovskite solar cell is gaining interest in lead-free perovskite solar cells as it is less toxic as compared to lead but possess almost all the characteristics of a perfect solar cell materials. Within 5 years, the reported efficiency of tin-based solar cells has increased from 6.4% to 9%. Although facing with stability issues as it is easily oxidised in ambient air, several studies have proven that the stability issues can be reduced. One of it is by using cesium as the ‘A’ cation. On the other hand, although studies on germanium-based perovskite solar cells are rarely conducted, promising results are shown when it is alloyed with tin producing narrower bandgaps and better stability owing to the protection of the GeO2 surface layer.
IOP Conference Series: Materials Science and Engineering, 2019
Ag/TiO2 thin film was prepared by the sol-gel method through the hydrolysis of titanium tetraisop... more Ag/TiO2 thin film was prepared by the sol-gel method through the hydrolysis of titanium tetraisopropoxide and silver nitrate solution. Various amount of PEG was doped into the solution preparation to study the effect on crystalline state and microstructural of the prepared thin films. Spin coating method was used to get uniform film on ITO glass substrate followed by annealing process for 1 hour. The obtained thin films were analysed using XRD test, SEM and AFM. Results showed that all the prepared thin films are in anatase TiO2 Increasing the PEG amount into the solution could increase the thickness and surface roughness of the obtained thin films.
Thin-film solar cell Absorption in Si x Ge 1Àx layers Bandgap engineering Hetero-junction solar c... more Thin-film solar cell Absorption in Si x Ge 1Àx layers Bandgap engineering Hetero-junction solar cells Heteroepitaxial growth of Si x Ge 1Àx on Si a b s t r a c t Crystalline silicon (c-Si) solar cell represents a cost effective, environment-friendly, and proven renewable energy resource. Industrially manufacturing of c-Si solar has now matured in terms of efficiency and cost. Continuing cost-effective efficiency enhancement requires transition towards thinner wafers in near term and thin-films in the long term. Successful implementation of either of these alternatives must address intrinsic optical absorption limitation of Si. Bandgap engineering through integration with Si x Ge 1Àx layers offers an attractive, inexpensive option. With the help of PC1D software, role of Si x Ge 1Àx layers in conventional c-Si solar cells has been intensively investigated in both wafer and thin film configurations by varying Ge concentration, thickness, and placement. In wafer configuration, increase in Ge concentration leads to enhanced absorption through bandgap broadening with an efficiency enhancement of 8% for Ge concentrations of less than 20%. At higher Ge concentrations, despite enhanced optical absorption, efficiency is reduced due to substantial lowering of open-circuit voltage. In 5-25-lm thickness, thin-film solar cell configurations, efficiency gain in excess of 30% is achievable. Therefore, Si x Ge 1Àx based thin-film solar cells with an order of magnitude reduction in costly Si material are ideally-suited both in terms of high efficiency and cost. Recent research has demonstrated significant improvement in epitaxially grown Si x Ge 1Àx layers on nanostructured Si substrates, thereby enhancing potential of this approach for next generation of c-Si based photovoltaics.
Crystalline silicon (c-Si) solar cell dominates 90% of photovoltaic (PV) market. The c-Si is the ... more Crystalline silicon (c-Si) solar cell dominates 90% of photovoltaic (PV) market. The c-Si is the most mature of all PV technologies and expected to remain leading the PV technology by 2050. The attractive characters of Si solar cell are stability, long lasting and higher lifetime. Presently, the efficiency of c-Si solar cell is still stuck at 25% for one and half decades. Tandem approach is one of the attempts to improve the Si solar cell efficiency with higher bandgap layer is stacked on top of Si bottom cell. Perovskite offers a big potential to be inserted into a tandem solar cell. Perovskite with bandgap of 1.6 to 1.9 eV will be able to absorb high energy photons, meanwhile c-Si with bandgap of 1.124 eV will absorb low energy photons. The high carrier mobility, high carrier lifetime, highly compatible with both solution and evaporation techniques makes perovskite an eligible candidate for perovskite-Si tandem configuration. The solution of methyl ammonium lead iodide (MAPbI3) was prepared by single st...
The back-contact crystalline silicon solar cell represents an advanced configuration in which int... more The back-contact crystalline silicon solar cell represents an advanced configuration in which interdigitated positive and negative contacts are placed on the rear surface. Highest conversion efficiency, elimination of shading losses, co-planarity of cell interconnections, and uniform black appearance, represent some of the most significant features of this type of solar cell. However, the manufacturing process complexity leads to significantly higher production cost making it difficult to compete with conventional mono and poly crystalline Si-based Photovoltaics industry. Over the years, an increasing number of researchers have reported on methods and processes aimed at reduction in manufacturing cost. This review paper attempt an extensive review of several categories of back-contact silicon solar cells, relevant design innovations, specific cost advantages especially in terms of using lower lifetime materials, their efficiency advantages in terms of geometry and wafer type, and their manufacturing technologies. In addition, available simulation tools for numerical investigation on back-contact structures and advanced device concepts have also presented in order to better understand underlying physical considerations in terms of passivation, both surface and volume, and minority carrier lifetime.
In this paper, a respond surface methodology (RSM) model has been developed using three levels Bo... more In this paper, a respond surface methodology (RSM) model has been developed using three levels Box-Benkhen experimental design (BBD) technique to study the influence of several metal-assisted chemical etching (MACE) process variables on the properties of nanostructured silicon (Si) wafer. Five process variables are examined i.e. concentrations of silver (Ag), hydrofluoric acid (HF), deposition time, H2O2 concentration and etching time as a function of etching rate. Design-Expert® software (version 7.1) is used in formulating the RSM model of five factors with 46 experiments. A regression quadratic model is developed to correlate the process variables where the most significant factors are identified and validated using analysis of variance (ANOVA). The model for etching rate is found to be significant with R2 of 0.8, where both Ag concentrations and etching time are the major influence.
The porous silicon etching creates a thin layer of nanowires that enhances the absorption and red... more The porous silicon etching creates a thin layer of nanowires that enhances the absorption and reduces the reflectance of light. In this work we present porous silicon nanowires were fabricated on doublesided of n-type Si (111) wafers with 525 µm thickness using a single step metal assisted chemical etching process. Two different resistivity (Ω=50-100 cm, Ω= >3000 cm) of wafer was involved in this study with different etching time (10, 20, 30, 40 min). The properties of porous silicon structure changed with increase time of etching. The investigation of the porous silicon nanowires structure revealed that the formation of nanowires depends on the doping concentration of the wafers. We make a preliminary determination as the light trapping properties for samples with etching time 10 min for low resistivity and 20 min for high resistivity. A different mechanism of slow charge trapping was observed using Kelvin Probe measurement. We show conclusively that the charge generated at the interface charge occurs by illumination on short length of nanowires (<405nm) and low surface roughness (<35 nm) for both resistivity of the wafers.
High quality Ge and Si x Ge 1-x films grown on Si substrates are attractive for a wide range of a... more High quality Ge and Si x Ge 1-x films grown on Si substrates are attractive for a wide range of applications in optics, optoelectronics, and high efficiency solar cells. In this study, heteroepitaxial growth of Ge on nanostructured Si surfaces has been investigated. Thermally evaporated amorphous Ge films are vacuum-deposited and crystallized by thermal annealing at 1000 °C. Scanning electron microscope (SEM), spectroscopy (RS), infrared (IR) transmission, and Raman methods are used to characterize amorphous and crystalline Ge films. SEM analysis reveals presence of dominant features including cracks, microscopic roughness, and islands. RS exhibits strong multiple peaks attributed to crystalline structures related to Si-Ge at ~ 444 cm-1 and Ge at 300 cm-1 ; narrow and stronger peaks are observed in thermally annealed films. A comparison of IR transmission measurements in 900-1700-nm spectral range shows that amorphous film absorption is significantly higher than that of crystalline films consistent with respective bandgaps. A more detailed analysis including EDX and XRD measurements will be presented at the conference.
Role of micro and nanostructures in enhancing IR transmission in Si wafers has been investigated.... more Role of micro and nanostructures in enhancing IR transmission in Si wafers has been investigated. Based on feature dimensions, incident light interaction can be described in terms of: (a) geometrical optics for wavelengths significantly smaller than surface dimensions, (b) diffractive optics for wavelengths comparable to surface features, and (c) physical optics for wavelengths substantially larger than surface features. Randomly distributed features in micro and nanoscale regimes were fabricated on identical Si wafers. A simple IR optical transmission system based on InGaAs photodetector and monochromator was developed for optical measurements. Optical transmission near the bandgap was substantially reduced by randomly distributed nanostructures likely attributed to diffractive optics. At the conference, details of several structures along with their reflection and transmission measurements will be presented in order to determine optimum surfaces for lowest transmission near the bandgap.
Fenton process is one of the advanced oxidation processes (AOPs) used to remove complex organic p... more Fenton process is one of the advanced oxidation processes (AOPs) used to remove complex organic pollutants in wastewater. In this study, instead of iron sulfate (FeSO 4), nano zero valent iron (nZVI) was used as a major source of ferrous iron (Fe 2+). In order to enhance the process, ultrasound was utilized in this study. Results show that, with the aid of ultrasound, nZVI produced more Fe 2+ compared to FeSO 4 at pH 2. Furthermore, combination of higher intensity and longer sonication time in Fenton process acceleratde the chemical oxygen demand (COD) removal from palm oil mill effluent (POME). Through the process, 80% of COD content was removed within 2 hours instead of 24 hours of silent degradation.
Proceedings of the 3rd WSEAS International Conference on Energy Planning, Energy Saving, Environmental Education, EPESE
Abstract:–Meteorological data has been used in determining of global and diffuse solar radiation ... more Abstract:–Meteorological data has been used in determining of global and diffuse solar radiation for years. Various methods have been developed and proved to be accurately comparable to the measured value. Among all, the most common meteorological parameter used are cloud cover, sunshine duration hours and number of rainy days, A review of various methods used in determination of global solar radiation by using cloud cover is presented in this paper.
Abstract:-Satellite images have been indentified as an alternative and accurate method for predic... more Abstract:-Satellite images have been indentified as an alternative and accurate method for predicting average annual daily solar radiation of a specific location. These images can be use to predict the performance and sizing of various solar energy systems such as solar thermal and photovoltaic applications. The data from satellite images are used and compared with the actual readings from solar instruments. The results are then used to estimate solar intensity for other places where solar instrument is not available. Malaysia ...
The prevailing opinion among the scholars is that history as a study should determine the politic... more The prevailing opinion among the scholars is that history as a study should determine the politics of memory and serve as a model for the narratives of collective identity. However, it should be remembered that memory and history, despite their close relationship, have different goals and realize different functions in society. Historical science cannot define the collective memory, but must participate in shaping the politics of memory. The task of historical politics is precisely to cut off multiplicity in order to provide an opportunity for action, while the task of historical science as a whole is to preserve and increase the potential of multiplicity to provide a wide choice of possible actions.
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