Brahim Aissa - Academia.edu (original) (raw)

Papers by Brahim Aissa

Journal of Nanoparticle Research, Apr 24, 2017

Zinc oxide (ZnO) nanostructures were successfully grown directly on single walled carbon nanotube... more Zinc oxide (ZnO) nanostructures were successfully grown directly on single walled carbon nanotubes (SWCNT) template through the CO 2 laserinduced chemical liquid deposition (LCLD) process. Photoluminescence (PL) of the deposited ZnO/ SWCNT hybrid composites exhibits, at room temperature, a narrow near UV band located at 390 nm with no emission bands in the visible region, indicating a high degree of crystalline quality of the ZnO nanostructures. Moreover, when the relative SWCNT loads are varied within the composites, the PL intensity and the diffused optical reflectance diminish in comparison with those of ZnO alone, owing to the transfer of photo-excited electrons from ZnO to the SWCNT, and the enhancement of the optical absorbance, respectively. Finally, these ZnO/ SWCNT hybrid composites are integrated into a heterojunction photovoltaic-based device, using PEDOT:PSS on ITO/glass substrate. The devices show an evident p-n junction behavior in the dark, and a clear I-V curve shift downward when illuminated with an open-circuit voltage of 1.1 V, a short circuit current density of 14.05 μA cm −2 , and a fill factor of ∼35%. These results indicate that these composites fabricated via LCLD process could be promising for optoelectronic and energy-harvesting devices.

Journal of Applied Physics, Sep 24, 2015

We report the memory operation behavior of a light illumination ambipolar single-walled carbon na... more We report the memory operation behavior of a light illumination ambipolar single-walled carbon nanotube thin film field-effect transistors devices. In addition to the high electronic-performance, such an on/off transistor-switching ratio of 10 4 and an on-conductance of 18 lS, these memory devices have shown a high retention time of both hole and electron-trapping modes, reaching 2.8 Â 10 4 s at room temperature. The memory characteristics confirm that light illumination and electrical field can act as an independent programming/erasing operation method. This could be a fundamental step toward achieving high performance and stable operating nanoelectronic memory devices. V

Journal of Materials Research, Nov 1, 2009

Interrelationship between the structure and optical properties of graphite-like semiconductor car... more Interrelationship between the structure and optical properties of graphite-like semiconductor carbon nitride produced by the heat treatment of thiocarbamide in an oxygen-containing medium at temperatures in the range from 400°C to 625°C is established. It is found that the maximum of the photoluminescence band shifts from 417 to 494 nm and simultaneously broadens, as the temperature of synthesis is elevated to 625°C. This effect is attributed to doping with oxygen and to the formation of defects as a consequence of decomposition of the already synthesized material with increasing temperature.

Frontiers in nanoscience and nanotechnology, 2015

Solar photovoltaic (PV) energy is one of the main renewable energy sources, and crystalline silic... more Solar photovoltaic (PV) energy is one of the main renewable energy sources, and crystalline silicon presently dominates completely this field. To date, the positively doped (p-type) crystalline silicon (c-Si) wafers have occupied most of the solar PV market. However, cells made with n-type crystalline silicon wafers are actually more efficient. This is because the material properties offered by n-type crystalline silicon substrates are suitable for higher efficiencies. Properties such as the absence of boron-oxygen related defects and a greater tolerance to key metal impurities by n-type crystalline silicon substrates are major factors that allow these better efficiencies. This yields a better bulk minority carrier lifetime, therefore, the performance of commercial photovoltaic n-type Si devices is strongly controlled by the surface and contact quality. A well-designed solar cell processing sequence can mitigate their effects to yield high efficiency devices. We propose here a review of the properties of defects, impurities, and impurity-defect interactions that can occur during crystal growth and device processing, as well as the high-efficiency fabrication process flow allowed by the use of n-type c-Si.

Photovoltaic Technology for Hot and Arid Environments

Materials Advances

A direct impact of the growth temperature, the nucleation and growth rates on the morphology, cry... more A direct impact of the growth temperature, the nucleation and growth rates on the morphology, crystallinity, orientation and optical properties of the ZnO NRs arrays. A simulated optimum photo-conversion efficiency of 15.48% is achieved in ZnO NRs of 1.1 μm in length.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Since fibre optic sensors (FOS) use dielectric materials they can be used in harsh environment co... more Since fibre optic sensors (FOS) use dielectric materials they can be used in harsh environment conditions; such as high voltage, high electromagnetic radiation, or high temperature. In this chapter, we review the basic concepts and processes related to FOS and some examples of doping materials used to improve the fibre sensitivity.

Self-Healing Materials: From fundamental concepts to advanced space and electronics applications, 2019

Various methods are used for the evaluation of the healing efficiency. One of the three fracture ... more Various methods are used for the evaluation of the healing efficiency. One of the three fracture modes (i.e., Mode I, II or III, Figure 5.1) is induced in two sets of devices. The first set of devices includes samples from the original host material; the second set includes samples containing the self-healing agent and the catalyst. After the healing process is completed, a standard test is performed to compare the two sets of the devices. A second test can be run in parallel, or separately, to validate the results from the first test. Some of the common tests used to measure self-healing efficiency are as follows: stretching the sample up to its rupture; three and four-point flexure bend tests; indentation tests; ballistic test with projectile; hypervelocity impact test; accelerated aging damage tests.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Harsh environments conditions, long-term distributed sensing and long-term sensing implementation... more Harsh environments conditions, long-term distributed sensing and long-term sensing implementations are a few typical examples where the characteristics of a sensing system which is optical has advantageous and can make an effective and more relevant solution as compared to a conventional electrical sensors system. In this chapter, we will briefly focus on the temperature measurement applications of fibre Bragg grating (FBG) sensors, together with their behaviour under high mechanical compression and gamma irradiation.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

In this chapter, we introduce and review the technology of Bragg gratings in optical fibres. We d... more In this chapter, we introduce and review the technology of Bragg gratings in optical fibres. We detail the aspect of photosensitivity in optical fibres, the properties of Bragg gratings, and the main developments in devices and applications. The most dominant fabrication techniques, including interferometric, phase mask and point-by-point are developed and their respective advantages/disadvantages discussed accordingly.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

This chapter gives an overview of state-of-the-art measurement systems based on frequency standar... more This chapter gives an overview of state-of-the-art measurement systems based on frequency standards and optical fibre sensing (OFS) with regard to satellite interrogation system. The fibre sensing interrogator provides six external sensor channels. Four of the channels support fibres that accommodate up to four fibre Bragg grating (FBG) sensors each, the fifth and sixth channels read out one high temperature and one combined pressure/temperature (P/T) sensor, respectively.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Harsh environments, distributed systems, space and long-term deployments are typical examples whe... more Harsh environments, distributed systems, space and long-term deployments are typical examples where the characteristics of the fibre Bragg grating FBG systems can make provide the clear advantage and a highly effective solution as compared to conventional electrical sensors.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Following the enormous development of the fibre Bragg grating(s) (FBG) sensor technology in the r... more Following the enormous development of the fibre Bragg grating(s) (FBG) sensor technology in the recent years, different kinds of fibre optic sensors (FOS) with advanced faculties were designed and matured to sense various parameters, including temperature, radiation, rotation, strain, acceleration, vibration, humidity, refractive index (RI) and so on. In this chapter, we will detail and review the main applications of FBG sensors while putting focus on the communications field.

Smart Materials and Structures, 2020

Investigation on self-healing properties of epoxy containing microcapsules of pure 5-ethylidene-2... more Investigation on self-healing properties of epoxy containing microcapsules of pure 5-ethylidene-2-norbornene (5E2N) and mixed multi-walled carbon nanotube (MWCNT) suspension is presented in this work using lap shear and mode I fracture tests. While both systems show significant self-healing functionalities between 39% and 97%, those repaired with MWCNT/5E2N microcapsules are found to have mechanical recovery efficiencies two times higher than those containing 5E2N alone, under different types of loading. MWCNT/5E2N microcapsules are also found to improve the physical strength of the epoxy matrix much higher than microcapsules containing only 5E2N. Compared to self-healing epoxy systems made of 5E2N microvessels, the dispersion of 0.10 wt.% of only MWCNTs inside the encapsulated monomer increases the lap shear strengths of the pristine materials and the self-healing materials tested after one fracture/curing cycle, by about 50% and 250%, respectively. Using fractographic observations...

Self-Healing Materials: From fundamental concepts to advanced space and electronics applications, 2019

The space environment is quite hostile to structural materials. The lifetime of space-craft is de... more The space environment is quite hostile to structural materials. The lifetime of space-craft is determined by the environmentally induced degradation of the structural materials. The self-healing systems discussed in this book chapter are applied mainly to polymer matrix-based materials. They usually include a variety of epoxies, polyimides, polysulfones and phenolics. In particular, cyanate-ester resins have been considered due to their lower hygrostrain/outgassing compared to the first generation of epoxy matrices. Carbon, glass and aramid fibres have also been used as reinforcing filaments within composite space structures. Aramid fibres are often employed as a `buffer' within a shielding system against damage induced by micrometeoroid impacts.

ACS Omega, 2021

We report on the optical and morphological properties of silica thin layers deposited by reactive... more We report on the optical and morphological properties of silica thin layers deposited by reactive RF magnetron sputtering of a SiO 2 target under different oxygen to total flow ratios [r(O 2) = O 2 /Ar, ranging from 0 to 25%]. The refractive index (n), extinction coefficient, total transmission, and total reflectance were systematically investigated, while field-emission scanning electron microscopy, atomic force microscopy, and threedimensional (3D) average roughness data construction measurements were carried out to probe the surface morphology. Contact angle measurements were performed to assess the hydrophilicity of our coatings as a function of the oxygen content. We performed a thorough numerical analysis using 1D-solar cell capacitance simulator (SCAPS-1D) based on the measured experimental optical properties to simulate the photovoltaic (PV) device performance, where a clear improvement in the photoconversion efficiency from 25 to 26.5% was clearly observed with respect to r(O 2). Finally, a computational analysis using OptiLayer confirmed a minimum total reflectance of less than 0.4% by coupling a silica layer with n = 1.415 with another high-refractive-index (i.e., >2) oxide layer. These promising results pave the way for optimization of silica thin films as efficient antireflection and self-cleaning coatings to display better PV performance in a variety of locations including a desert environment.

Journal of Photonics for Energy, 2020

Abstract. A low-temperature solution process technique is employed to develop an inorganic cesium... more Abstract. A low-temperature solution process technique is employed to develop an inorganic cesium carbonate (Cs2CO3) as an electron transport material for inorganic–organic hybrid double cation (FAPbI3)0.85(MAPbBr3)0.15 perovskite solar cells, as an alternative to the conventional thick and meso-TiO2. A device structure of compact-TiO2/Cs2CO3 (0.2 wt. %)/perovskite/spiro-OMETAD leads to enhanced performance of the photovoltaic device, achieving a short-circuit current density (Jsc) of 22.26 mA/cm2, an open-circuit voltage (Voc) of 1054 mV, a fill factor (FF) of 71.6%, and a power conversion efficiency (PCE) of about 17% under one sun illumination, whereas the controlled device structure shows an efficiency of 16.58% without such surface modification layer. Additionally, a device structure of Cs2CO3 (6 wt. %)/perovskite/spiro-OMETAD without any TiO2 ETM has shown a Jsc of 15.40 mA/cm2, Voc of 1023 mV, FF of 51.7%, and a PCE of 8.14%. On the other hand, external quantum efficiency (EQE) data yields around 85% of incident photon to electron conversion for c-TiO2/Cs2CO3 (0.2 wt. %)/perovskite/spiro-OMETAD structure and integrated Jsc extracted from EQE data confirms that Jsc obtained from the current–voltage test is within a close agreement. The obtained results indicate that there is a possibility to further increase the performance of perovskite-based cells and reduce their processing cost by replacing the thick mesoporous TiO2 by Cs2CO3.

Scientific Reports, 2020

We report the successful microencapsulation of multi-walled carbon nanotubes suspended in a 5-eth... more We report the successful microencapsulation of multi-walled carbon nanotubes suspended in a 5-ethylidene-2-norbornene (5E2N) self-healing monomer, into poly melamine urea formaldehyde shells through in situ polymerization. The average size of the microcapsules, their size-distribution, shell wall structural integrity and thickness are characterized by optical and scanning electron microscopy. The presence of carbon nanotubes (CNTs) inside the core liquid content, as well as their release after breaking is confirmed by microscopy and spectroscopy analyses. A small amount of CNTs inside the microcapsules is found to have no significant impact on the thermal stability of the system, as determined by thermogravimetric analysis and differential scanning calorimetry. Both the mechanical and the electrical properties of CNT-based self-healing materials can be restored up to 80% when CNT/5E2N microcapsules are incorporated into polymer composites, thus making them highly suitable for appl...

Self-Healing Materials From fundamental concepts to advanced space and electronics applications, 2019

In this chapter, the main experimental results obtained to date on the selfhealing composite mate... more In this chapter, the main experimental results obtained to date on the selfhealing composite materials are reviewed. The review starts with the nanostructuration of the ruthenium Grubbs' catalyst (RGC) by means of the laser ablation process, followed by the encapsulation of the 5-ethylidene-2norbornene (ENB) liquid monomer into small capsules and the fabrication of three-dimensional (3D) microvascular nanocomposite beams by microfluidic infiltration. Special attention is given to the use of single-wall carbon nanotubes (SWCNT) material as reinforcement of the ENB healing agent from the perspective of obtaining a self-healing composite material with improved mechanical properties and, at the same time, having a fast ring-opening metathesis polymerisation (ROMP) reaction with high mechanical properties.

ACS Applied Energy Materials, 2019

We report independently confirmed 22.15% and record 22.58% power conversion efficiencies, for thi... more We report independently confirmed 22.15% and record 22.58% power conversion efficiencies, for thin (130 μm-140 μm) p-and n-type mono-like Si solar cells, respectively. We comparatively assessed advanced n-type and p-type mono-like silicon wafers for potential use in low-cost high-efficiency solar cell applications by using phosphorus diffusion gettering for material-quality improvement and silicon heterojunction solar cell fabrication for assessment of performance in high-efficiency photovoltaic device architecture. We show that gettering improves material quality and device properties significantly, depending on the type of doping (n-type or ptype), wafer position in the ingot, drive-in temperature and cooling profile. Owing to the high open circuit voltage (725 mV), the record n-type solar cell also represents the highest reported solar cell efficiency for cast silicon to date.

Journal of Nanoparticle Research, Apr 24, 2017

Zinc oxide (ZnO) nanostructures were successfully grown directly on single walled carbon nanotube... more Zinc oxide (ZnO) nanostructures were successfully grown directly on single walled carbon nanotubes (SWCNT) template through the CO 2 laserinduced chemical liquid deposition (LCLD) process. Photoluminescence (PL) of the deposited ZnO/ SWCNT hybrid composites exhibits, at room temperature, a narrow near UV band located at 390 nm with no emission bands in the visible region, indicating a high degree of crystalline quality of the ZnO nanostructures. Moreover, when the relative SWCNT loads are varied within the composites, the PL intensity and the diffused optical reflectance diminish in comparison with those of ZnO alone, owing to the transfer of photo-excited electrons from ZnO to the SWCNT, and the enhancement of the optical absorbance, respectively. Finally, these ZnO/ SWCNT hybrid composites are integrated into a heterojunction photovoltaic-based device, using PEDOT:PSS on ITO/glass substrate. The devices show an evident p-n junction behavior in the dark, and a clear I-V curve shift downward when illuminated with an open-circuit voltage of 1.1 V, a short circuit current density of 14.05 μA cm −2 , and a fill factor of ∼35%. These results indicate that these composites fabricated via LCLD process could be promising for optoelectronic and energy-harvesting devices.

Journal of Applied Physics, Sep 24, 2015

We report the memory operation behavior of a light illumination ambipolar single-walled carbon na... more We report the memory operation behavior of a light illumination ambipolar single-walled carbon nanotube thin film field-effect transistors devices. In addition to the high electronic-performance, such an on/off transistor-switching ratio of 10 4 and an on-conductance of 18 lS, these memory devices have shown a high retention time of both hole and electron-trapping modes, reaching 2.8 Â 10 4 s at room temperature. The memory characteristics confirm that light illumination and electrical field can act as an independent programming/erasing operation method. This could be a fundamental step toward achieving high performance and stable operating nanoelectronic memory devices. V

Journal of Materials Research, Nov 1, 2009

Interrelationship between the structure and optical properties of graphite-like semiconductor car... more Interrelationship between the structure and optical properties of graphite-like semiconductor carbon nitride produced by the heat treatment of thiocarbamide in an oxygen-containing medium at temperatures in the range from 400°C to 625°C is established. It is found that the maximum of the photoluminescence band shifts from 417 to 494 nm and simultaneously broadens, as the temperature of synthesis is elevated to 625°C. This effect is attributed to doping with oxygen and to the formation of defects as a consequence of decomposition of the already synthesized material with increasing temperature.

Frontiers in nanoscience and nanotechnology, 2015

Solar photovoltaic (PV) energy is one of the main renewable energy sources, and crystalline silic... more Solar photovoltaic (PV) energy is one of the main renewable energy sources, and crystalline silicon presently dominates completely this field. To date, the positively doped (p-type) crystalline silicon (c-Si) wafers have occupied most of the solar PV market. However, cells made with n-type crystalline silicon wafers are actually more efficient. This is because the material properties offered by n-type crystalline silicon substrates are suitable for higher efficiencies. Properties such as the absence of boron-oxygen related defects and a greater tolerance to key metal impurities by n-type crystalline silicon substrates are major factors that allow these better efficiencies. This yields a better bulk minority carrier lifetime, therefore, the performance of commercial photovoltaic n-type Si devices is strongly controlled by the surface and contact quality. A well-designed solar cell processing sequence can mitigate their effects to yield high efficiency devices. We propose here a review of the properties of defects, impurities, and impurity-defect interactions that can occur during crystal growth and device processing, as well as the high-efficiency fabrication process flow allowed by the use of n-type c-Si.

Photovoltaic Technology for Hot and Arid Environments

Materials Advances

A direct impact of the growth temperature, the nucleation and growth rates on the morphology, cry... more A direct impact of the growth temperature, the nucleation and growth rates on the morphology, crystallinity, orientation and optical properties of the ZnO NRs arrays. A simulated optimum photo-conversion efficiency of 15.48% is achieved in ZnO NRs of 1.1 μm in length.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Since fibre optic sensors (FOS) use dielectric materials they can be used in harsh environment co... more Since fibre optic sensors (FOS) use dielectric materials they can be used in harsh environment conditions; such as high voltage, high electromagnetic radiation, or high temperature. In this chapter, we review the basic concepts and processes related to FOS and some examples of doping materials used to improve the fibre sensitivity.

Self-Healing Materials: From fundamental concepts to advanced space and electronics applications, 2019

Various methods are used for the evaluation of the healing efficiency. One of the three fracture ... more Various methods are used for the evaluation of the healing efficiency. One of the three fracture modes (i.e., Mode I, II or III, Figure 5.1) is induced in two sets of devices. The first set of devices includes samples from the original host material; the second set includes samples containing the self-healing agent and the catalyst. After the healing process is completed, a standard test is performed to compare the two sets of the devices. A second test can be run in parallel, or separately, to validate the results from the first test. Some of the common tests used to measure self-healing efficiency are as follows: stretching the sample up to its rupture; three and four-point flexure bend tests; indentation tests; ballistic test with projectile; hypervelocity impact test; accelerated aging damage tests.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Harsh environments conditions, long-term distributed sensing and long-term sensing implementation... more Harsh environments conditions, long-term distributed sensing and long-term sensing implementations are a few typical examples where the characteristics of a sensing system which is optical has advantageous and can make an effective and more relevant solution as compared to a conventional electrical sensors system. In this chapter, we will briefly focus on the temperature measurement applications of fibre Bragg grating (FBG) sensors, together with their behaviour under high mechanical compression and gamma irradiation.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

In this chapter, we introduce and review the technology of Bragg gratings in optical fibres. We d... more In this chapter, we introduce and review the technology of Bragg gratings in optical fibres. We detail the aspect of photosensitivity in optical fibres, the properties of Bragg gratings, and the main developments in devices and applications. The most dominant fabrication techniques, including interferometric, phase mask and point-by-point are developed and their respective advantages/disadvantages discussed accordingly.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

This chapter gives an overview of state-of-the-art measurement systems based on frequency standar... more This chapter gives an overview of state-of-the-art measurement systems based on frequency standards and optical fibre sensing (OFS) with regard to satellite interrogation system. The fibre sensing interrogator provides six external sensor channels. Four of the channels support fibres that accommodate up to four fibre Bragg grating (FBG) sensors each, the fifth and sixth channels read out one high temperature and one combined pressure/temperature (P/T) sensor, respectively.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Harsh environments, distributed systems, space and long-term deployments are typical examples whe... more Harsh environments, distributed systems, space and long-term deployments are typical examples where the characteristics of the fibre Bragg grating FBG systems can make provide the clear advantage and a highly effective solution as compared to conventional electrical sensors.

Fibre Bragg Gratings in Harsh and Space Environments: Principles and applications, 2019

Following the enormous development of the fibre Bragg grating(s) (FBG) sensor technology in the r... more Following the enormous development of the fibre Bragg grating(s) (FBG) sensor technology in the recent years, different kinds of fibre optic sensors (FOS) with advanced faculties were designed and matured to sense various parameters, including temperature, radiation, rotation, strain, acceleration, vibration, humidity, refractive index (RI) and so on. In this chapter, we will detail and review the main applications of FBG sensors while putting focus on the communications field.

Smart Materials and Structures, 2020

Investigation on self-healing properties of epoxy containing microcapsules of pure 5-ethylidene-2... more Investigation on self-healing properties of epoxy containing microcapsules of pure 5-ethylidene-2-norbornene (5E2N) and mixed multi-walled carbon nanotube (MWCNT) suspension is presented in this work using lap shear and mode I fracture tests. While both systems show significant self-healing functionalities between 39% and 97%, those repaired with MWCNT/5E2N microcapsules are found to have mechanical recovery efficiencies two times higher than those containing 5E2N alone, under different types of loading. MWCNT/5E2N microcapsules are also found to improve the physical strength of the epoxy matrix much higher than microcapsules containing only 5E2N. Compared to self-healing epoxy systems made of 5E2N microvessels, the dispersion of 0.10 wt.% of only MWCNTs inside the encapsulated monomer increases the lap shear strengths of the pristine materials and the self-healing materials tested after one fracture/curing cycle, by about 50% and 250%, respectively. Using fractographic observations...

Self-Healing Materials: From fundamental concepts to advanced space and electronics applications, 2019

The space environment is quite hostile to structural materials. The lifetime of space-craft is de... more The space environment is quite hostile to structural materials. The lifetime of space-craft is determined by the environmentally induced degradation of the structural materials. The self-healing systems discussed in this book chapter are applied mainly to polymer matrix-based materials. They usually include a variety of epoxies, polyimides, polysulfones and phenolics. In particular, cyanate-ester resins have been considered due to their lower hygrostrain/outgassing compared to the first generation of epoxy matrices. Carbon, glass and aramid fibres have also been used as reinforcing filaments within composite space structures. Aramid fibres are often employed as a `buffer' within a shielding system against damage induced by micrometeoroid impacts.

ACS Omega, 2021

We report on the optical and morphological properties of silica thin layers deposited by reactive... more We report on the optical and morphological properties of silica thin layers deposited by reactive RF magnetron sputtering of a SiO 2 target under different oxygen to total flow ratios [r(O 2) = O 2 /Ar, ranging from 0 to 25%]. The refractive index (n), extinction coefficient, total transmission, and total reflectance were systematically investigated, while field-emission scanning electron microscopy, atomic force microscopy, and threedimensional (3D) average roughness data construction measurements were carried out to probe the surface morphology. Contact angle measurements were performed to assess the hydrophilicity of our coatings as a function of the oxygen content. We performed a thorough numerical analysis using 1D-solar cell capacitance simulator (SCAPS-1D) based on the measured experimental optical properties to simulate the photovoltaic (PV) device performance, where a clear improvement in the photoconversion efficiency from 25 to 26.5% was clearly observed with respect to r(O 2). Finally, a computational analysis using OptiLayer confirmed a minimum total reflectance of less than 0.4% by coupling a silica layer with n = 1.415 with another high-refractive-index (i.e., >2) oxide layer. These promising results pave the way for optimization of silica thin films as efficient antireflection and self-cleaning coatings to display better PV performance in a variety of locations including a desert environment.

Journal of Photonics for Energy, 2020

Abstract. A low-temperature solution process technique is employed to develop an inorganic cesium... more Abstract. A low-temperature solution process technique is employed to develop an inorganic cesium carbonate (Cs2CO3) as an electron transport material for inorganic–organic hybrid double cation (FAPbI3)0.85(MAPbBr3)0.15 perovskite solar cells, as an alternative to the conventional thick and meso-TiO2. A device structure of compact-TiO2/Cs2CO3 (0.2 wt. %)/perovskite/spiro-OMETAD leads to enhanced performance of the photovoltaic device, achieving a short-circuit current density (Jsc) of 22.26 mA/cm2, an open-circuit voltage (Voc) of 1054 mV, a fill factor (FF) of 71.6%, and a power conversion efficiency (PCE) of about 17% under one sun illumination, whereas the controlled device structure shows an efficiency of 16.58% without such surface modification layer. Additionally, a device structure of Cs2CO3 (6 wt. %)/perovskite/spiro-OMETAD without any TiO2 ETM has shown a Jsc of 15.40 mA/cm2, Voc of 1023 mV, FF of 51.7%, and a PCE of 8.14%. On the other hand, external quantum efficiency (EQE) data yields around 85% of incident photon to electron conversion for c-TiO2/Cs2CO3 (0.2 wt. %)/perovskite/spiro-OMETAD structure and integrated Jsc extracted from EQE data confirms that Jsc obtained from the current–voltage test is within a close agreement. The obtained results indicate that there is a possibility to further increase the performance of perovskite-based cells and reduce their processing cost by replacing the thick mesoporous TiO2 by Cs2CO3.

Scientific Reports, 2020

We report the successful microencapsulation of multi-walled carbon nanotubes suspended in a 5-eth... more We report the successful microencapsulation of multi-walled carbon nanotubes suspended in a 5-ethylidene-2-norbornene (5E2N) self-healing monomer, into poly melamine urea formaldehyde shells through in situ polymerization. The average size of the microcapsules, their size-distribution, shell wall structural integrity and thickness are characterized by optical and scanning electron microscopy. The presence of carbon nanotubes (CNTs) inside the core liquid content, as well as their release after breaking is confirmed by microscopy and spectroscopy analyses. A small amount of CNTs inside the microcapsules is found to have no significant impact on the thermal stability of the system, as determined by thermogravimetric analysis and differential scanning calorimetry. Both the mechanical and the electrical properties of CNT-based self-healing materials can be restored up to 80% when CNT/5E2N microcapsules are incorporated into polymer composites, thus making them highly suitable for appl...

Self-Healing Materials From fundamental concepts to advanced space and electronics applications, 2019

In this chapter, the main experimental results obtained to date on the selfhealing composite mate... more In this chapter, the main experimental results obtained to date on the selfhealing composite materials are reviewed. The review starts with the nanostructuration of the ruthenium Grubbs' catalyst (RGC) by means of the laser ablation process, followed by the encapsulation of the 5-ethylidene-2norbornene (ENB) liquid monomer into small capsules and the fabrication of three-dimensional (3D) microvascular nanocomposite beams by microfluidic infiltration. Special attention is given to the use of single-wall carbon nanotubes (SWCNT) material as reinforcement of the ENB healing agent from the perspective of obtaining a self-healing composite material with improved mechanical properties and, at the same time, having a fast ring-opening metathesis polymerisation (ROMP) reaction with high mechanical properties.

ACS Applied Energy Materials, 2019

We report independently confirmed 22.15% and record 22.58% power conversion efficiencies, for thi... more We report independently confirmed 22.15% and record 22.58% power conversion efficiencies, for thin (130 μm-140 μm) p-and n-type mono-like Si solar cells, respectively. We comparatively assessed advanced n-type and p-type mono-like silicon wafers for potential use in low-cost high-efficiency solar cell applications by using phosphorus diffusion gettering for material-quality improvement and silicon heterojunction solar cell fabrication for assessment of performance in high-efficiency photovoltaic device architecture. We show that gettering improves material quality and device properties significantly, depending on the type of doping (n-type or ptype), wafer position in the ingot, drive-in temperature and cooling profile. Owing to the high open circuit voltage (725 mV), the record n-type solar cell also represents the highest reported solar cell efficiency for cast silicon to date.