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Deeply etched laser texturing for enhancement of optical absorption in p-type silicon solar cells

Thu, 15 Sep 2022 00:00:00 GMT

Title: Deeply etched laser texturing for enhancement of optical absorption in p-type silicon solar cells Authors: Nurfarizza Surhada Mohd Nasir, P78575 Abstract: Structural design with high light absorption is a major challenge for thin silicon solar cells. Thin silicon solar cells acquire incomplete incident light absorption because the bandgap inadvertently has incomplete light absorption due to the indirect bandgap. The deeply etched micro-texture structure or deep scratch laser micro-texture (DELMS) in the cell architecture absorbs all visible light and collects electron-hole-generated photos to increase the efficiency of the solar cell. DELMS is designed using a simple and nontoxic fabrication method to form the texture of deep scratch surfaces. The front and back wafer surfaces are scratched due to laser radiation forming a range of microtextured with different width depths and crystallographic defects. The crystallographic defects resulting from laser radiation were modified using chemicals for the post-texture process. Silicon dioxide was deposited thermally on the surface of the wafer as an antireflection coating (ARC). The cell structure was analysed using SILVACO simulation based on the experimental data of the transmitter layer produced by phosphoric acid using the doctor blade method. The doctor blade method dispersed at a safe temperature of 875 °C for 30min was selected based on the optimal characterization of dopant densities greater than 1019cm-3. Next, the back surface field (BSF) was generated by Aluminium paste, while the front structure was generated by Argentum paste dispersed at 750 °C for 60 seconds. The diffusion lengths for planar and laser surface textures are 209.14μm and 278.00μm. The increase was about 32.94% for the laser surface texture compared to the plane surface. Meanwhile, the lifespan of the minority carrier for planar and laser surface textures is about 16.20μs and 28.60μs. The deep laser engraved texture showed an increase in the lifetime of about 76.54% compared to plane surface silicon solar cells. Moreover, light current-voltage (LIV) measurements showed the microtexture of deep laser scratches increased by about 10.00% compared to conventional planar fabrication processes for silicon solar cells. Thus, modifications to the wafer texture have the ability to increase the conversion efficiency through a deep laser scratch micro-textured that enables internal dispersion and increases the optical path length in the sidewall of the silicon solar cell. Description: Fulltext

Penjerapan ion nikel dan kuprum oleh semikonduktor asid akrilik -cantuman-nanofiber polianilina

Tue, 26 Sep 2023 00:00:00 GMT

Title: Penjerapan ion nikel dan kuprum oleh semikonduktor asid akrilik -cantuman-nanofiber polianilina Authors: Sabariah Kamarudin (P78625) Abstract: Sisa air yang mengandungi logam berat merupakan ancaman kepada kesihatan awam dan alam sekitar. Polianilina (PANI) merupakan bahan penjerap yang boleh digunakan semula sebagai polimer konduktif atau penebat selepas proses penjerapan. Teknik konvensional seperti pempolimeran percampuran deras dapat menghasilkan PANI yang lebih banyak, manakala pempolimeran antara muka menghasilkan nanofiber polianilina (PANI NF) yang bersaiz lebih kecil. Projek ini menggunakan kaedah pempolimeran pengoksidaan dengan ammonium persulfat sebagai agen pengoksida. Kajian ini membuktikan bahawa PANI NF boleh dihasilkan melalui kaedah hibrid dengan menggabungkan kedua-dua teknik konvensional tersebut tanpa kontaminasi surfaktan. Kaedah hibrid ini dapat memberikan hasil nanofiber dengan saiz antara 20-30 nm. PANI NF dicirikan menggunakan FESEM, XRD, FTIR dan kaedah kesan Hall. Walau bagaimanapun, PANI NF yang memiliki ciri hidrofobik menghalang kebolehan penjerapan dalam larutan akua. Maka, pempolimeran cantuman dilakukan pada PANI NF bagi memberikan ciri hidrofilik pada permukaannya sekaligus meningkatkan penjerapan. Penyinaran pancaran elektron digunakan bagi mencantumkan asid akrilik (AA) pada permukaan PANI NF bagi menyediakan kumpulan berfungsi khusus untuk membantu penjerapan. Teknik yang cekap dan mesra alam ini memberikan peratusan cantuman optimum sehingga 78%. Selain itu, kajian terhadap interaksi antara ion-ion logam dan asid akrilik-cantuman-nanofiber polianilina (AA-g-PANI NF) dalam larutan akua melalui kajian kinetik dan isoterma juga dilakukan. AA-g-PANI NF mempamerkan sifat penjerapan yang baik terhadap ion nikel dan kuprum. Mekanisme penjerapan kedua-dua ion logam melibatkan tiga langkah: penjerapan awal yang cepat, diikuti dengan pengambilan logam yang lebih perlahan dan akhirnya, tiada pengambilan ion logam disebabkan kesemua liang telah dipenuhi. Proses penjerapan adalah mengikut model kinetik pseudo-tertib-kedua dan data keseimbangan penjerapan adalah mengikut isoterma Langmuir. Kapasiti penjerapan maksimum bagi ion nikel adalah 112.36 mg/g manakala bagi ion kuprum pula adalah 44.84 mg/g. Kajian kinetik dan isoterma terhadap AA-g-PANI NF menggambarkan penjerapan kimia berlaku secara monolapis. Kesimpulannya, AA-g-PANI NF yang disediakan menggunakan kaedah hibrid berpotensi digunakan dalam penjerapan ion logam dari sisa air. AA-g-PANI NF yang telah terjerap juga berpotensi untuk diguna semula menjadi polimer yang berfungsi sebagai konduktif atau penebat. Description: Full-text

Evaluation of molybdenum disulfide (MoS2) as the back layer for the silicon heterojunction solar cell (SHJ)

Mon, 01 Jul 2024 00:00:00 GMT

Title: Evaluation of molybdenum disulfide (MoS2) as the back layer for the silicon heterojunction solar cell (SHJ) Authors: Elsmani, Mohammed Islam Gamar Eldien Wahab Allah Elshiekh (P101262) Abstract: Silicon heterojunction solar cells (SHJ) are one of the promising photovoltaic technologies due to their high efficiency, structural symmetric processibility, and low thermal coefficient. Despite SHJ advantages, free carrier absorption (FCA) and light reflection effects in the near-infrared (NIR) light spectrum demerits SHJ and are reportedly caused by the front and back SHJ's transparent conductive oxides (TCOs). Therefore, this dissertation endeavoured to evaluate Molybdenum disulfide (MoS2) as a back layer in an SHJ to reduce the TCOs NIR free carrier absorption effect (FCA). The simulated and optimized MoS2 thickness on SHJ using Sunsolve raytracing software demonstrated that 2D-MoS2 improves the SHJ's efficiency by about 0.004 % (rel.), which is insignificant. Conversely, a comparative study using Atlas-Silvaco software revealed a similar optical and electronic results trend. However, Atlas showed better electronic results than the Sunsolve model with the (2D)-MoS2 efficiency improvement difference of ~ 3.10% (rel.) over the reference SHJ, thanks to the wellsimulated electronic junctions. In collaborative works, the practical application of twodimensional (2D)-MoS2 underwent contact engineering through n-type doping using Dichloromethane as an n-doping agent, shifting the equilibrium state fermi level towards the conduction edge. In contrast, gold nanoparticles (AuNPs) were employed as a p-doping agent for MoS2. However, where the latter was effective doping, the required Schottky barrier lowering can be achieved only with the n-doping since MoS2 is on the backside of the SHJ solar cell. Furthermore, it offered a better charge carrier extraction lifetime and reduced the Schottky barrier compared with pristine MoS2. As a result of the increased Jsc due to the NIR light management and contact engineering, the power conversion efficiency (PCE) results for SHJ incorporated MoS2 (SHJ/MoS2) was improved from 11.45% to 13.03 %. External quantum efficiency (EQE) and reflectance results suggest MoS2 constructive NIR light interference with back layers improved light current density (Jsc). Overall, the experimental results consented to the simulation results, possibly due to the actual Schottky height barrier lowering. This suggests that the 2D Transition Metal Dichalcogenides (TMDC) materials may have a potential for solar cell applications with effective contact engineering techniques with proper SunsVoc characterization to evaluate the implied Voc and its effects on the cell's performance metrics along the SHJ contact management setup. Description: Full-text

Performance enhancement of a straight-bladed vertical axis wind turbine utilizing a wedge flap

Tue, 01 Oct 2024 00:00:00 GMT

Title: Performance enhancement of a straight-bladed vertical axis wind turbine utilizing a wedge flap Authors: Abdalkarem, Asmail Abdulkadr Mohamed (P96192) Abstract: Urban areas are major contributors to carbon emissions. Vertical axis wind turbines, such as Darrieus turbines, can be effectively used in urban conditions to provide renewable energy, thereby reducing dependence on fossil fuels. However, the low power coefficient (CP) of this type of turbine has been identified as a main drawback that limits its application. Many researchers have proposed various airfoil modifications aimed at enhancing aerodynamic characteristics and limiting unsteady interactions with the atmospheric boundary layer. The current study evaluated the potential of adding a wedge flap (WF) at the trailing edge (TE) of the NACA 0021 airfoil numerically and experimentally using a wind tunnel. The effect of different WF configurations—on one side and two sides, as well as variations in height, angle, and optimal length-to-height (L/H)—on the aerodynamic performance and flow over the airfoil was studied systematically using two-dimensional computational fluid dynamics (CFD) simulation. Subsequently, the rotor blades were manufactured using a three-dimensional printer, considering the optimal WF dimensions derived from CFD simulation. The effect of adding the WF was then tested experimentally in a small wind tunnel at different wind speeds. The results indicate that the addition of the WF can effectively suppress flow separation and enhance aerodynamic efficiency across all studied cases compared to the clean airfoil. The aerodynamic performance is significantly influenced by the height of the WF, while the length at L/H < 1 has a relatively minor effect. The inclined WF achieved the highest lift and lift-to-drag ratios, with total maximum increments of 71.67% and 45.79%, respectively, at optimal height and length of 6%c and 1%c, respectively, compared to the clean airfoil case. The experimental results show that adding the WF at the TE of the blades can substantially improve the CP at different wind speeds. A WF appears to be an effective passive flow control device that can be used in new wind turbines or retrofitted to existing ones, provided its dimensions are properly selected. Description: Full-text