Browsing by Author "Zekry, Abdelhalim"

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Analysis of Hybrid Hetero-Homo Junction Lead-Free Perovskite Solar Cells by SCAPS Simulator
(MDPI, 09/12/2021) Salem, Marwa. S; Shaker, Ahmed; Zekry, Abdelhalim; Abouelatta, Mohamed; Alanazi, Adwan; Alshammari, Mohammad T; Gontand, Christian
In this work, we report on the effect of substituting the active intrinsic i-layer on a conventional pin structure of lead-free perovskite solar cell (PSC) by a homo p-n junction, keeping the thickness of the active layer constant. It is expected that when the active i-layer is substituted by a p-n homo junction, one can increase the collection efficiency of the photo-generated electrons and holes due to the built-in electric field of the homo junction. The impact of the technological and physical device parameters on the performance parameters of the solar cell have been worked out. It was found that p-side thickness must be wider than the n-side, while its acceptor concentration should be slightly lower than the donor concentration of the n-side to achieve maximum efficiency. In addition, different absorber types, namely, i-absorber, n-absorber and p-absorber, are compared to the proposed pn-absorber, showing a performance-boosting effect when using the latter. Moreover, the proposed structure is made without a hole transport layer (HTL) to avoid the organic issues of the HTL materials. The back metal work function, bulk trap density and ETL material are optimized for best performance of the HTL-free structure, giving Jsc = 26.48, Voc = 0.948 V, FF = 77.20 and PCE = 19.37% for AM1.5 solar spectra. Such results highlight the prospective of the proposed structure and emphasize the importance of using HTL-free solar cells without deteriorating the efficiency. The solar cell is investigated by using SCAPS simulator.
Design considerations of CdSe solar cells for indoor applications under white LED illumination
(Elsevier B.V, 2024-07) Salem, Marwa S; Shaker, Ahmed; Okil, Mohamed; Li, Luying; Chen, Chao; Aledaily, Arwa N; Al-Dhlan, Kawther A; Zekry, Abdelhalim
This work sheds light on the potential of Cadmium Selenide (CdSe) solar cells for indoor applications. CdSe boasts a wide direct bandgap, high carrier mobility, and a high absorption coefficient, making it an attractive candidate for harnessing ambient indoor light. Our study centers around an experimental solar cell architecture composed of FTO/CdSe/PEDOT:PSS/CuI/ITO, which exhibits a power conversion efficiency (PCE) of 6.00 %. Through a meticulous analysis of the core technological aspects of this cell, we successfully replicate the measured current-voltage characteristics and other experimental data, affirming the validity of our simulation modeling approach. Moving forward, we delve into the design and optimization of CdSe-based solar cells under white LED illumination. We emphasize the pivotal role of a double-hole transport layer (HTL) configuration over a single HTL, with a focus on optimizing the alignment between the HTL/back contact and HTL/absorber interfaces. The strategic incorporation of a heavily doped p-type HTL material, boasting both a deep valence band maximum (VBM) and a shallow conduction band minimum (CBM), is identified as paramount, especially for a deep VBM absorber like CdSe. Adding double HTL materials also facilitates efficient hole collection within the CdSe thin film while mitigating undesirable electron-hole recombination at the critical interface between the hole collection layer and the electrode. The implementation of a double HTL configuration based on CuI/ZnTe:Cu or CuI/BCS significantly enhances performance, resulting in a PCE in the order of 20 % under 200 lux and 2900 K LED illumination. Moreover, we introduce the single HTL design to provide other alternatives for efficiency boosting. Upon increasing the work function of the front contact, it is found that the valence band offset between the HTL and the absorber can be engineered, resulting in a PCE above 21.5 %.
Investigation of Base High Doping Impact on the npn Solar Cell Microstructure Performance using Physically Based Analytical Model
(IEEE, 2021-01) Marwa S, Salem; Zekry, Abdelhalim; Shaker, Ahmed
Recently, there is a rapid trend to incorporate low cost solar cells in photovoltaic technology. In this regard, low-cost high-doped Silicon wafers are beneficial; however, the high doping effects encountered in these wafers render their practical use in fabrication. The npn solar cell microstructure has been found to avoid this issue by the proper design of vertical generation and lateral collection of the light generated carriers. We report on the impact of the p+ base doping concentration, up to 2×1019 cm-3, on the npn microstructure performance to find the most appropriate way for high efficiency. To optimize the structure, a series of design steps has been applied using our previously published analytical model. Before inspecting the high doped base effect, firstly, the n+ emitter is optimized. Secondly, the impact of bulk recombination inside the p+ base is introduced showing the range of optimum base width (Wp). Then, we investigate thoroughly the impact of base doping levels for different base widths to get the optimum Wp that satisfies maximum efficiency. The results show that for p+ base doping concentration ranging from 5×1017 cm-3 to 2×1019 cm-3, the npn microstructure efficiency decreases from 15.9% to 9%, respectively. Although the efficiency is degraded considerably for higher doping levels, the structure still achieves a competitive efficiency at higher doping levels, for which its cost is greatly reduced, in comparison with thin film solar cells. Moreover, using higher doping permits lesser wafer area which could be beneficial for large area solar cells design.
On the Investigation of Interface Defects of Solar Cells: Lead-based vs Lead-free Perovskite
(IEEE Access, 2021) Salem, Marwa. S; Salah, Mostafa M; Mousa, Mohamed; Shaker, Ahmed; Zekry, Abdelhalim; Abouelatta, Mohamed; Alshammari, Mohammad T; Al-Dhlan, Kawther A; Gontrand, Christian
Perovskite solar cells (PSCs) have drawn significant consideration as a competing solar cell technology because of the drastic advance in their power conversion efficiency (PCE) over the last two decades. The interfaces between the electron transport layer (ETL) and the absorber layer and between the absorber layer and the hole transport layer (HTL) have a major impact on the performance of the PSCs. In this paper, we have investigated the defect interfaces between ETL/absorber layer and absorber layer/HTL of calibrated experimental lead-based and lead-free PSCs. The influence of the defect interfaces is studied in order to find the optimum value for the maximum possible PCE. While the PCE has not been enhanced considerably for the lead-based, it is boosted from 1.76% to 5.35% for lead-free PSCs. Also, bulk traps were found to have minor role in comparison with interface traps for the lead-free cell while they have a significant impact for the lead-based cell. The results presented in this work would shed some light on designing interface defects of various types of practical PSC structures and demonstrates the crucial impact of the interface defects on lead-free vs lead-based PSCs. All simulation studies are performed by using SCAPS-1D simulator.
An Overview of the Development of Speaker Recognition Techniques for Various Applications
(Engineering and Technology Publishing, 2022-08) Mohamed, Amira; Eltokhy, Amira; Zekry, Abdelhalim
Speech Enhancement (SE) is a significant research issue in audio signal processing where the goal is to enhance the clarity and quality of speech signals corrupted by noise. Because of its different applications, it becomes a compelling research topic nowadays. The focus of this paper is dedicated to one of these applications which is Speaker recognition. In this paper, the fundamentals and applications of speaker recognition are discussed. A brief study on the performance and the recognition accuracy of different speaker modeling techniques has been conducted. Furthermore, while there have been several studies about the technologies used in speaker recognition, there have been few studies about the applications of speaker recognition, and none of them considers combining or linking the applications and technology in the same study. This overview demonstrates the various technologies that can be used to achieve speaker recognition applications. It aims to give a new perspective of the existing technologies uses in various applications. The paper concludes with discussions on future trends and research opportunities in this area. © 2022 Journal of Communications and 2022 by the authors.
Performance Improvement of npn Solar Cell Microstructure by TCAD Simulation: Role of Emitter Contact and ARC
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-09) Marwa S, Salem; Zekry, Abdelhalim; Shaker, Ahmed; Abouelatta, Mohamed; Almurayziq, Tariq S; Alshammari, Mohammad T; El-Banna, Mohamed M
In the current study, the performance of the npn solar cell (SC) microstructure is improved by inspecting some modifications to provide possible paths for fabrication techniques of the structure. The npn microstructure is simulated by applying a process simulator by starting with a heavily doped p-type substrate which could be based on low-cost Si wafers. After etching deep notches through the substrate and forming the emitter by n-type diffusion, an aluminum layer is deposited to form the emitter electrode with about 0.1 µm thickness; thereby, the notches are partially filled. This nearly-open-notches microstructure, using thin metal instead of filling the notch completely with Al, gives an efficiency of 15.3%, which is higher than the conventional structure by 0.8%. Moreover, as antireflection coating (ARC) techniques play a crucial role in decreasing the front surface reflectivity, we apply different ARC schemes to inspect their influence on the optical performance. The influence of utilizing single layer (ZnO), double (Si3N4/ZnO), and triple (SiO2/Si3N/ZnO) ARC systems is investigated, and the simulation results are compared. The improvement in the structure performance because of the inclusion of ARC is evaluated by the relative change in the efficiency (∆η). In the single, double, and triple ARC, ∆η is found to be 12.5%, 15.4%, and 17%, respectively. All simulations are performed by using a full TCAD process and device simulators under AM1.5 illumination.
Performance Investigation of a Proposed Flipped npn Microstructure Silicon Solar Cell Using TCAD Simulation
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-07) Salem, Marwa S; Zekry, Abdelhalim; Shaker, Ahmed; Abouelatta, Mohamed; ElBanna, Mohamed M; Almurayziq, Tariq S; Ramadan, Rabie A; Alshammari, Mohammad T
This work aims at inspecting the device operation and performance of a novel flipped npn microstructure solar cell based on low-cost heavily doped silicon wafers. The flipped structure was designed to eliminate the shadowing effect as applied in the conventional silicon-based interdigitated back-contact cell (IBC). Due to the disappearance of the shadowing impact, the optical performance and short-circuit current density of the structure have been improved. Accordingly, the cell power conversion efficiency (PCE) has been improved in comparison to the conventional npn solar cell microstructure. A detailed analysis of the flipped npn structure was carried out in which we per- formed TCAD simulations for the electrical and optical performance of the flipped cell. Additionally, a comparison between the presented flipped microstructure and the conventional npn solar cell was accomplished. The PCE of the conventional npn structure was found to be 14.5%, while it was about 15% for the flipped structure when using the same cell physical parameters. Furthermore, the surface recombination velocity and base bulk lifetime, which are the most important recombination parameters, were studied to investigate their influence on the flipped microstructure performance. An efficiency of up to 16% could be reached when some design parameters were properly fine-tuned. Moreover, the impact of the different physical models on the performance of the proposed cell was studied, and it was revealed that band gap narrowing effect was the most significant factor limiting the open-circuit voltage. All the simulations accomplished in this analysis were carried out using the SILVACO TCAD process and device simulators.
Utilization of decimation interpolation strategy for medical image communication and storage
(IEEE, 2018) Abd ElSamie, Fathi ElSayed; Al-Zubi, Nayel; Zekry, Abdelhalim; Elmisery, F. A; Ebied, Mostafa
In storing large databases of images such as medical databases, the required memory size becomes a great challenge. This paper presents a framework for reducing the size of large stored medical images. Among available methods, the Joint Photographic Experts Group (JPEG) has moderate performance as it is a lossy standard. It only compresses a single picture with intra-coding, and it does not utilize the inter-frame correlation among pictures. The Set Partitioning in Hierarchical Trees (SPIRT) algorithm is a refined version of the Embedded Zero Wavelet (EZW) algorithm. It can perform better with higher compression ratios for a wide variety of images than those of the EZW. In this paper, the decimation is adopted as a compression process to minimize the size of stored images. Interpolation is used to recover images for further processing. Different interpolation schemes can be used for this purpose. A comparative study between different polynomial interpolation methods is presented for the objective of reconstructing the images. The experimental results show that the proposed decimation interpolation strategy yields good reconstruction performance, presents good compression ratios in the decimation process, and introduces acceptable PSNR values in the reconstruction process.
Validation and Evaluation of a Behavioral Circuit Model of an Enhanced Electrostatic MEMS Converter
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-06) Salem, Mona S; Zekry, Abdelhalim; Abouelatta, Mohamed; Shaker, Ahmed; Salem, Marwa S
In this current study, the validation and evaluation of a behavioral circuit model of electro- static MEMS converters are presented. The main objective of such a model is to accurately find the converter behavior through the proper choice of its circuit elements. In this regard, the model enables the implementation of the electrostatic MEMS converter using commercially available off-shelf circuit elements. Thus, the overall vibration energy harvesting system can be implemented and tested with- out the need for fabricating the converter. As a result, the converter performance can be verified and evaluated before its fabrication which saves the expenses of fabricating trailed prototypes. To test the model, we apply it to an enhanced converter in which the conventional electrostatic MEMS converter is modified by depositing the tantalum pentoxide, Ta2O5 , a high dielectric constant material, on its fingers’ sidewalls. Such a deposition technique causes an appreciable increase in the overall converter capacitance and, in turn, the output power, which is boosted from the range of µw to the range of mW. Next, the converter behavioral circuit model, which is based on representing its capacitances variations with respect to the input displacement, x caused by the vibration signal, C–x curve, is built up. The model is qualitatively validated and quantitatively evaluated. The enhanced converter performance is investigated through the interaction of its model with the power conditioning circuit. From the simulation results, it is revealed that the converter behavioral circuit model accurately accomplishes the vibration energy conversion operation. As a result, the specification of the required controlling pulses for the converter operation is accurately determined. Finally, the model accuracy is validated by calibrating its performance with a traditionally simulated and fabricated electrostatic MEMS converter.