Browsing by Author "Salem, Marwa S"

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Analysis and design of p-n homojunction Sb2Se3 solar cells by numerical simulation
(Elsevier Ltd., 2022-07) Shaker, Ahmed; Salem, Marwa S; Jayan, K. Deepthi
Antimony selenide (Sb2Se3) is considered a promising candidate utilized as an absorber in thin film solar cell (TFSC) technology thanks to its non-toxic and earth-abundant nature besides its reported high absorption co- efficient. To enhance the power conversion efficiency (PCE) of Sb2Se3 solar cells, we report some design sug- gestions by applying device simulation. The numerical model is firstly validated by calibration of simulation results vs those from an experimental Sb2Se3 solar cell structure composed of FTO/CdS/Sb2Se3/Au where CdS serves as an electron transport layer (ETL). Then, the cell is modified to include an embedded p-n homojunction. In contrast to the conventional heterostructure design, a homojunction structure has crucial benefits in terms of both electronic and optoelectronic characteristics such as the extra produced built-in electric field which can increase the transport of photogenerated carriers. Three device configurations are presented and compared. The first and the second cases are when using CdS and ZnOS as ETLs. Utilizing ZnOS ternary compound is found to be more beneficial as its conduction band offset with the absorber layer could be tuned to attain a proper cliff-like band alignment. The third case is when considering homojunction design free from all carrier transport layers. Possible paths for device optimization are investigated to boost the efficiency in a try to overcome the efficiency bottleneck encountered in the Sb2Se3-based quasi homojunction solar cells. All simulations, performed in this study, are done by SCAPS device simulation software under standard AM1.5G one Sun illumination
Automatic Control of a Mobile Manipulator Robot Based on Type-2 Fuzzy Sliding Mode Technique
(MDPI AG, 2022-10) Xu, Xin; Shaker, Ahmed; Salem, Marwa S
In this paper, an automatic control method based on type-2 fuzzy sliding mode control for a mobile arm robot is presented. These types of robots have very complex dynamics due to the uncertainty of the arm parameters and the mobility of their base, so conventional control methods do not provide a suitable solution. The proposed method proves convergence with Lyapunov theory, and its convergence is mathematically guaranteed. A type-2 fuzzy system is responsible for approximating unmodulated dynamics, nonlinear terms, and uncertain parameters. In simulations, the performance of the proposed method with different situations, including uncertainty in arm parameters, uncertainty in mobile robot parameters (arm robot base), uncertainty in load, as well as indeterminacy in modeling have been applied. The comparison with two conventional controllers shows the efficiency and superiority of the proposed method.
Bandwidth Broadening of Piezoelectric Energy Harvesters Using Arrays of a Proposed Piezoelectric Cantilever Structure
(MDPI AG, 8/17/2021) Salem, Marwa S; Ahmed, Shimaa; Shaker, Ahmed; Alshammari, Mohammad T; Al-Dhlan, Kawther A; Alanazi, Adwan; Saeed, Ahmed; Abouelatta, Mohamed
One of the most important challenges in the design of the piezoelectric energy harvester is its narrow bandwidth. Most of the input vibration sources are exposed to frequency variation during their operation. The piezoelectric energy harvester’s narrow bandwidth makes it difficult for the harvester to track the variations of the input vibration source frequency. Thus, the harvester’s output power and overall performance is expected to decline from the designed value. This current study aims to solve the problem of the piezoelectric energy harvester’s narrow bandwidth. The main objective is to achieve bandwidth broadening which is carried out by segmenting the piezoelectric material of the energy harvester into n segments; where n could be more than one. Three arrays with two, four, and six beams are shaped with two piezoelectric segments. The effect of changing the length of the piezoelectric material segment on the resonant frequency, output power, and bandwidth, as well as the frequency response is investigated. The proposed piezoelectric energy harvesters were implemented utilizing a finite element method (FEM) simulation in a MATLAB environment. The results show that increasing the number of array beams increases the output power and bandwidth. For the three-beam arrays, at n equals 2, 6 mW output power and a 9 Hz bandwidth were obtained. Moreover, the bandwidth of such arrays covered around 5% deviation from its resonant frequency. All structures were designed to operate as a steel wheel safety sensor which could be used in train tracks. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Comprehensive design and analysis of thin film Sb2S3/CIGS tandem solar cell: TCAD simulation approach
(IOP Publishing Ltd, 2024-06) Salem, Marwa S; Shaker, Ahmed; Aledaily, Arwa N; Alanazi, Adwan; Al-Dhlan, Kawther A; Okil, Mohamed
This research presents a design and analysis of a tandem solar cell, combining thin film wide bandgap Sb2S3 (1.72 eV) and narrow bandgap CIGS (1.15 eV) for the top and bottom sub-cells, respectively. The integration of all thin film layers enhances flexibility, rendering the tandem solar cell suitable for applications such as wearable electronics. To optimize the power conversion efficiency (PCE) of the tandem solar device, advanced technology computer-aided design (TCAD) simulation tools are employed to estimate loss mechanisms and fine-tune parameters for each layer. An experimentally validated optoelectronic model is introduced, calibrated and validated against fabricated reference solar cells for the individual top and bottom cells. The calibrated model is then utilized to propose optimization routines for the Sb2S3/CIGS tandem solar cell. The initial tandem cell exhibits a JSC of 15.72 mA cm−2 and a PCE of 15.36%. The efficiency drop in the tandem configuration is identified primarily in the top cell. A systematic optimization process for the top cell is initiated, exploring various configurations, including HTL-free and ETL-free setups. Moreover, an np homojunction structure for the top cell is proposed. Optimization routines are applied that involve determining optimal thickness and doping concentration of the n-layer, investigating the effect of p-layer doping concentration, and exploring the influence of the work function of the front contact. As a result, the tandem cell efficiency is significantly improved to 23.33% at the current matching point (CMP), with a J SC of 17.15 mA cm−2. The findings contribute to the advancement of thin-film tandem solar cell technology, showcasing its potential for efficient and flexible photovoltaic applications .
Design and analysis of Sb2S3/Si thin film tandem solar cell
(Elsevier, 2023-01) Okil, M.; Shaker, Ahmed; Ahmed, Ibrahim S; Abdolkader, Tarek M; Salem, Marwa S
Antimony sulfide (Sb2S3) and thin crystalline silicon (c-Si) are considered suitable top- and bottom-cell candi- dates for tandem solar cells (TSCs), owing to their natural abundance, non-toxicity, cost-competitiveness, and complementary bandgaps. The current work proposes and investigates a two-terminal (2T) monolithic Sb2S3/Si thin film TSC via TCAD simulation. The Sb2S3 cell, with a bandgap of 1.7 eV, is utilized as a top sub-cell, and the bottom sub-cell is utilized by a thin c-Si cell having a bandgap of 1.12 eV. The calibrated standalone top and bottom cells provide a power conversion efficiency (η) of 4.31% and 14.26%, respectively. Upon incorporating the two cells into a 2T Sb2S3/Si monolithic TSC, the resultant tandem cell achieves an η of 10.10% implying that the top cell should be optimized in order to get a tandem efficiency higher than the bottom cell. Thus, the Sb2S3 cell is optimized by designing the cell without the organic hole transport layer (HTL) (resulting in an np het- erojunction) and engineering the conduction band offset (CBO) between the electron transport layer (ETL) and the Sb2S3 absorber. Then, the tandem structure is optimized starting from the ETL thickness and doping con- centration. Also, the impact of changing the absorber defect density and the series resistance of the top cell on the TSC performance is investigated to demonstrate the maximum available η. At reduced defect density and series resistance, the overall efficiency of the tandem cell is improved to 19.51%. Furthermore, we explored the impact of top and bottom absorber thicknesses on TSC working metrics. At the designed matching point, the tandem efficiency is enhanced to 23.25%, and Jsc also boosts to 17.24 mA/cm2 . The simulation study is intended to provide a tandem configuration that is based on an all-thin-film design which may be suitable for applications like wearable electronics due to its flexibility. All TCAD simulations are performed using the Silvaco Atlas simulator under standard one Sun (AM1.5G, 1000 W/m2 ) illumination.
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 %.
Design of n-i-p and p-i-n Sb2Se3 solar cells: role of band alignment
(IOP Publishing Ltd., 2023-09) Salem, Marwa S; Okil, Mohamed; Shaker, Ahmed; Albaker, Abdullah; Alturki, Mansoor
Investigations into novel device architectures and interfaces that enhance charge transport and collection are necessary to increase the power conversion efficiency (PCE) of antimony selenide (Sb2Se3) solar cells, which have shown great promise as a low-cost and high-efficiency alternative to conventional silicon-based solar cells. The current work uses device simulations to design p-i-n and n-i-p Sb2Se3-based solar cell structures. The n-i-p configuration is investigated by comparing distinct electron transport layer (ETL) materials to get the best performance. While certain ETL materials may yield higher efficiencies, the J–V curve may exhibit S-shaped behavior if there is a misalignment of the bands at the ETL/absorber interface. To address this issue, a proposed double ETL structure is introduced to achieve proper band alignment and conduction band offset for electron transport. A PCE of 20.15% was achieved utilizing (ZnO/ZnSe) as a double ETL and Spiro-OMeTAD as a hole transport layer (HTL). Further, the p-i-n configuration is designed by proposing a double HTL structure to facilitate hole transport and achieve a proper valence band offset. A double HTL consisting of (CuI/CuSCN) is used in conjunction with ETL-free configuration to achieve a PCE of 21.72%. The simulation study is conducted using the SCAPS-1D device simulator and is validated versus a previously fabricated cell based on the configuration FTO/CdS/Sb2Se3/Spiro-OMeTAD/Au.
Elucidation the effectiveness of acridine orange as light-harvesting layer for photosensing applications: Structural, spectroscopic and electrical investigations
(Elsevier, 2022-11) Salem, Marwa S; Wassel, Ahmed R; Fedawy, M; Shaker, A; Al-Bagawia, Amal H; Alanazi, Adwan; El-Mahalawy, Ahmed M
In this research, acridine orange, AO, bio-photosensitive thin films are prepared using vacuum thermal evapo- ration technique for optoelectronic applications. First, the crystal structure of the deposited films compared to powder is investigated using the XRD technique. Next, the surface morphology of the deposited AO thin film is characterized using the FESEM technique giving rise to a uniform, homogeneous, and granular polycrystalline film. The amplitude and spatial roughness parameters of the film are estimated. Furthermore, the optical properties of the deposited AO thin film are spectrophotometrically characterized in the range from UV to NIR. The recorded absorbance, transmittance, and reflectance showed high UV and visible absorption characteristics with a direct energy gap of ~2.238 eV. The optical constants, including refractive index and extinction coeffi- cient, are found, and the dispersion behavior is analyzed using the one-oscillator model for estimating the oscillator and dispersion energies. The dielectric function and dielectric relaxation time of AO thin film are interpreted in detail. In addition, an organic/inorganic heterogeneous junction based on Ag/AO/p-Si/Al is fabricated and electrically evaluated using the current-voltage relation. The fabricated heterojunction shows a rectification behavior of ideality factor, barrier height, and rectification ratio ~2.09, 0.707 eV, and 176, respectively. The charges dynamics mechanism in terms of band diagram and the density of interface states profile are analyzed. Eventually, the photoresponse of the engineered heterojunction is evaluated under the illumination of intensities that varies from 20 mW/cm2 to 100 mW/cm2 . The fabricated photosensor showed a high stable performance with responsivity, specific detectivity, linear dynamic range, and ON/OFF ratio of about 68.4 mA/W, 1.11 × 1010 Jones, 69.3 dB, and 108.4, respectively. The photoresponse performance of the present device is considered more efficient and stable than many other organic/inorganic photosensors.
Full optoelectronic simulation of all antimony chalcogenide thin film tandem solar cell: Design routes from 4-T to 2-T configuration
(Ain Shams University, 2024-06) Salem, Marwa S; Shaker, Ahmed; Chen, Chao; Li, Luying; Abouelatta, Mohamed; Aledaily, Arwa N; Zein, Walid; Okil, Mohamed
Antimony chalcogenide, as a newcomer to light harvesting materials, is regarded as an auspicious contender for incorporation as a photoactive layer in thin film tandem solar cells (TFTSCs). The current study introduces the design of all-antimony chalcogenide TFTSC comprised of an Sb2S3 (1.7 eV) front subcell and an Sb2Se3 (1.2 eV) rear subcell. The challenges to migrating from four-terminal (4-T) to two-terminal (2-T) designs are highlighted and possible solutions are proposed. To commence, a calibration procedure for the two subcells is conducted in alignment with experimental investigations. The benchmarked solar cells yield a power conversion efficiency (PCE) of 8.08 % for the upper subcell and 10.58 % for the lower subcell. Subsequently, upon integration of both subcells within the initial 4-T Sb2S3/Sb2Se3 TFTSC, the resultant PV cell attains a PCE of 12.27 %. Before transitioning it to a more efficient 2T tandem configuration, we explore alternative inorganic HTL materials to the Spiro-OMeTAD HTL to overcome its practical considerations. Cu2O is found to be the best HTL alternative to be included for both subcells. Upon stacking into the tandem structure, the combined cell exhibited an efficiency of 15.68 % and a notable Jsc of 16.23 mA/cm2 . To further enhance the tandem performance, the device structure is optimized by engineering the CBO of two sub-cells and employing a double ETL design for the front sub-cell. At the considered current matching criterion, the tandem device PCE and Jsc are boosted to 27.86 % and 17.60 mA/ cm2 , respectively. Based on this full optoelectronic analysis, developed in the Silvaco TCAD environment, a 2-T all antimony chalcogenide tandem configuration can be realized and optimized, paving the way for future experimental endeavors.
Full Optoelectronic Simulation of Lead-Free Perovskite/Organic Tandem Solar Cells
(MDPI AG, 2023-02) Salem, Marwa S; Shaker, Ahmed; Abouelatta, Mohamed; Saeed, Ahmed
Organic and perovskite semiconductor materials are considered an interesting combination thanks to their similar processing technologies and band gap tunability. Here, we present the design and analysis of perovskite/organic tandem solar cells (TSCs) by using a full optoelectronic simulator (SETFOS). A wide band gap lead-free ASnI2Br perovskite top subcell is utilized in conjunction with a narrow band gap DPPEZnP-TBO:PC61BM heterojunction organic bottom subcell to form the tandem configuration. The top and bottom cells were designed according to previous experimental work keeping the same materials and physical parameters. The calibration of the two cells regarding simulation and experimental data shows very good agreement, implying the validation of the simulation process. Accordingly, the two cells are combined to develop a 2T tandem cell. Further, upon optimizing the thickness of the front and rear subcells, a current matching condition is satisfied for which the proposed perovskite/organic TSC achieves an efficiency of 13.32%, Jsc of 13.74 mA/cm2 , and Voc of 1.486 V. On the other hand, when optimizing the tandem by utilizing full optoelectronic simulation, the tandem shows a higher efficiency of about 14%, although it achieves a decreased Jsc of 12.27 mA/cm2 . The study shows that the efficiency can be further improved when concurrently optimizing the various tandem layers by global optimization routines. Furthermore, the impact of defects is demonstrated to highlight other possible routes to improve efficiency. The current simulation study can provide a physical understanding and potential directions for further efficiency improvement for lead-free perovskite/organic TSC.
Harmonizing power systems with a 13-level modified Packed U-Cells multi-level inverter: Design and implementation
(Elsevier B.V, 2024-04) Fouda, Sherouk; Salem, Marwa S; Saeed, Ahmed; Shaker, Ahmed; Abouelatta, M; Abou El-Ela, M
Traditional multilevel inverter designs often face complexity challenges, prompting the need for a simplified solution. This study introduces and evaluates the performance of a Modified Packed U-Cells (MPUC) inverter in the realm of multilevel inverter technology. The study addresses challenges associated with conventional multilevel inverters and proposes the MPUC inverter as a solution to simplify the design complexity. The MPUC inverter, utilizing three DC sources and eight switches, presents a groundbreaking thirteen-level output waveform. The primary focus lies in assessing the inverter's performance in terms of Total Harmonic Distortion (THD) and output voltage. Utilizing MATLAB/Simulink, the inverter's performance is evaluated with and without Pulse Width Modulation (PWM) strategies. The results reveal a notable reduction in THD, from 26.25% to 9.91% post-filtering when PWM is not employed. Various multi-carrier Level-Shifted PWM strategies, including PDPWM, PODPWM, APODPWM, and COPWM, are explored to enhance output waveform smoothness and efficiency. Unequal Carrier strategies, specifically UEAPDPWM and UEAPODPWM, emerge as superior in THD management at different frequency ranges. The study further incorporates real-time hardware implementation of the proposed 13-level MPUC topology, highlighting the success of the UEAPD-PWM strategy in improving waveform quality. The research aims to establish a multilevel inverter design protocol meeting international standards and emphasizes the pivotal role of PWM techniques in enhancing waveform quality. This comprehensive evaluation contributes to advancing the field of multilevel inverter technology and sets a benchmark for future research in this domain.
Integration of biocompatible Coomassie Brilliant Blue dye on silicon in organic/Inorganic heterojunction for photodetection applications
(Elsevier Ltd., 2022-07) Salem, Marwa S; Wassel, Ahmed R; Fedawy, M; Shaker, A; Al-Bagawia, Amal H; Aleid, Ghada Mohamed; El-Mahalawy, Ahmed M
Here, we introduce systematic investigations of structural, morphological, and optical properties of solution- processed coomassie brilliant blue, CBB, thin films for photodetection applications. First, the structural and morphological features of the spin-coated CBB thin films are investigated using XRD and FESEM microscopy and yielded a polycrystalline, nanostructured, and porous CBB film of crystallite size and RMS roughness ~31.95 nm and 10.65 nm, respectively. The UV–Vis–NIR spectrophotometric measurements of transmittance and reflectance elucidated the efficient absorption and light-harvesting of the UV and visible light range with estimated indirect energy gap and Urbach energy ~1.54 eV and 22.3 meV, respectively. Next, the dispersion behavior of the fabricated thin films is analyzed in the light of the single-oscillator model estimating the detail dispersion pa- rameters. Furthermore, the dielectric function, as well as the nonlinear optical parameters, is accurately esti- mated. Subsequently, the microelectronic parameters of the engineered rectifying Ag/CBB/p-Si/Al heterojunction such as ideality factor, barrier height, series, and shunt resistances are estimated at different temperatures. The charges dynamical mechanism and the interface states density profile are analyzed, and the thermionic emission model is confirmed to fit the low bias region with a modified Richardson constant of about 34.8A/cm2 K2 .After that, the photoresponse of the implemented organic/inorganic heterojunction is checked at different illumination intensities and showed a significant stable sensitivity with fast On-Off switching behavior. The fabricated heterojunction achieved good figures of merit such as responsivity, specific detectivity, linear dynamic range, and rise/fall time of about 4.289 mA/W, 2.07 × 109 Jones, 30.36 dB, and 61.6/82.5 ms, respectively. The good and stable responsive performance of the current Ag/CBB/p-Si/Al architecture may make it a potential candidate for photodetection applications
A modified pseudo 2D physically-based model for double-gate TFETs: Role of precise calculations of drain and source depletion regions
(Elsevier, 7/14/2021) Yahia, Yasmin; Salem, Marwa S; Shaker, A; Kamel, H; Abouelatta, M; ElBanna, M
In this current study, a modified pseudo two-dimensional (2-D) semi-analytical model for double gate tunnel FETs (DG-TFETs) is introduced. The main regions in the DG-TFET structure are the channel and the depletion regions inside the source and the drain. In such regions, the 2-D Poisson’s equation is solved by adjusting suitable boundary conditions. The source and the drain depletion region lengths are calcu- lated precisely by an iterative technique resulting in an accurate prediction of the electrostatic potential. According to the obtained 2-D electrostatic potential, the energy band diagram could be extracted and, consequently, the minimum tunneling width is calculated. Accordingly, the model of drain current is introduced by applying Kane’s tunneling model. Further, the source depletion charge and the channel charge are derived, and the terminal capacitance components are then extracted. A comparison between the proposed model and SILVACO TCAD simulations shows a satisfactory agreement that confirms the validation of the presented model robustness. 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Ain Shams Uni- versity. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).
Narrowband Near-Infrared Perovskite/Organic Photodetector: TCAD Numerical Simulation
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-07) Salem, Marwa S; Shaker, Ahmed; Al-Bagawia, Amal H; Aleid, Ghada Mohamed; Othman, Mohamed S; Alshammari, Mohammad T; Fedawy, Mostafa
Narrowband photodetectors (PD) established in the near-infrared (NIR) wavelength range are highly required in a variety of applications including high-quality bioimaging. In this simulation study, we propose a filter-less narrowband PD based on the architecture of perovskite/organic het- erojunction. The most decisive part of the photodetector is the hierarchical configuration of a larger bandgap perovskite material with a thicker film followed by a lower bandgap organic material with a narrower layer. The design of the structure is carried out by TCAD numerical simulations. Our structure is based on an experimentally validated wideband organic PD, which is modified by invok- ing an additional perovskite layer having a tunable bandgap. The main detector device comprises of ITO/perovskite (CsyFA1−yPb(IxBr1−x)3 )/organic blend (PBDTTT-c:C60-PCBM)/PEDOT:PSS/Al. The simulation results show that the proposed heterojunction PD achieves satisfactory performance when the thickness of perovskite and organic layers are 2.5 µm and 500 nm, respectively. The designed photodetector achieves a narrow spectral response at 730 nm with a full width at half-maximum (FWHM) of 33 nm in the detector, while having a responsivity of about 0.12 A/W at zero bias. The presented heterojunction perovskite/organic PD can efficiently detect light in the wavelength range of 700 to 900 nm. These simulation results can be employed to drive the development of filter-less narrowband NIR heterojunction PD.
Numerical analysis and design of high performance HTL-free antimony sulfide solar cells by SCAPS-1D
(Elsevier, 07/12/2021) Salem, Marwa S; Shaker, Ahmed; Othman, Mohamed S; Al-Bagawia, Amal H; Fedawy, Mostafa; Aleid, Ghada Mohamed
Among the various absorbers encountered in thin film solar cells (TFSCs), antimony sulfide (Sb2S3) is considered a suitable candidate as it is a non-toxic and earth-abundant besides its high absorption coefficient. However, some critical issues cause its poor photovoltaic performance. These include unoptimized Sb2S3 layer, interface recombination and cell properties like the ineffective carrier collection and transport. To enhance the power conversion efficiency (PCE) of Sb2S3 solar cell, we suggest some design guidelines by employing device simulation. First, a calibration step is performed vs an experimental arrangement consists of FTO/TiO2/Sb2S3/Spiro-OMeTAD/Au to validate the simulation model. Next, as the organic hole transport material (HTM) often has poor long-term operation stability and demands high-cost fabrication processes, an HTL-free cell is proposed and designed by investigating the impact of the main technological and physical parameters. In the first step in the design of the HTL-free cell, we provide an affinity engineering methodology to tune the conduction band offset between the electron transport layer (ETL) and the absorber. Based on this approach, the most appropriate electron transport material (ETM) is chosen that fulfills the maximum efficiency. Then, an optimization routine is performed to select the most appropriate design parameters and the PCE of the optimized case is found to be about 22%. All simulations, carried out in this work, are performed by SCAPS-1D device simulator under AM1.5G illumination and 300 K temperature.
Numerical analysis of hole transport layer-free antimony selenide solar cells: Possible routes for efficiency promotion
(Elsevier, 2022-07) Salem, Marwa S; Shaker, Ahmed; Abouelatta, M; Alanazi, Adwan; Al-Dhlan, Kawther A; Almurayziq, Tariq S
Amongst the numerous absorbers confronted in thin-film solar cell technology, antimony selenide (Sb2Se3) is regarded as an extremely promising contender as it is a non-toxic and earth-abundant besides its high-level absorption coefficient. To boost the power conversion efficiency (PCE) of Sb2Se3 solar cells, we report some design recommendations by utilizing device simulation. The device model is firstly validated by calibration of an experimental cell having a configuration of FTO/CdS/Sb2Se3/Spiro-OMeTAD/Au. Then, the optimization of a hole transport layer (HTL) free structure is carried out by tuning the conduction band offset between the electron transport layer (ETL) and the Sb2Se3 absorber and by inspecting the key absorber parameters to get the maximum available power conversion efficiency. In this context, the ternary compound material ZnMgO is found to match the optimum band alignment. Moreover, the impact of ETL parameters, like thickness, doping, and surface treatment by ammonia etching, has been analyzed to understand its underlying physics and to provide possible ways for device efficiency promotion. All simulations, conducted in this paper, are accomplished by SCAPS device simulation software under standard one Sun (AM1.5G, 100 mW/cm2) illumination at 300 K.
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.
Performance optimization of high-K pocket hetero-dielectric TFET using improved geometry design
(Alexandria University, 2024-02) Elshamy, Abdelrahman; Shaker, Ahmed; Elogail, Yasmine; Salem, Marwa S; El Sabbagh, Mona
This study explores the optimization of a hetero-dielectric tunnel field-effect transistor (HDTFET) structure to improve device performance. By incorporating a high-k oxide pocket in a portion of the source-side gate insulator, a local minimum in the conduction band edge is induced at the source-channel interface. This technique leads to improved tunneling rates and increased current handling capability. The simulation analysis focuses on optimizing the position and dimension of the high-k dielectric pocket to enhance key device characterization metrics such as ON-state current (ION), ON-to-OFF-state current ratio (ION/IOFF), subthreshold swing (SS), and cutoff frequency (fT). The resulting optimized design for a 30 nm-channel length involves a pocket shift of 1 nm and a pocket length of 12 nm. This configuration achieves a remarkable ON current of 55 µA/µm, which is 30 times higher than that of a conventional TFET. Importantly, other analog performance parameters remain unaffected, with fT surpassing 175 GHz for the 30 nm-channel. Additionally, transient analysis is conducted by applying a resistive load inverter circuit to a pulse input. The fall propagation delay (tphl) exhibits a greater than two orders of magnitude enhancement, along with improved overshoot voltage (VP) compared to a TFET without a pocket. The study further explores the impact of supply scaling on transient parameters. Optimal pocket scalability concerning channel length is found to be 40% for pocket length and approximately 2.5% for pocket shift relative to the source-channel interface. The proposed design significantly enhances DC and analog as well as circuit-level metrics compared to the traditional uniform gate oxide TFET.
Prospective efficiency boosting of full-inorganic single-junction Sb2(S, Se)3 solar cell
(Elsevier BV, 2022-12) Salem, Marwa S; Shaker, Ahmed; Almurayziq, Tariq S.; Alshammari, Mohammad T.
Antimony selenosulfide, Sb2(S, Se)3, is regarded as an appropriate absorber to be utilized in terrestrial single junction solar cell applications thanks to the tunability of its bandgap energy which could be adjusted around 1.3 eV. To enhance the power conversion efficiency (PCE) of Sb2(S, Se)3-based single junction solar cell, we propose some design recommendations by using device simulation. First, in order to validate the simulation model, a calibration step is accomplished by comparing the numerical simulation results with those of a fabricated cell structure consisting of Au/Sb2(S, Se)3/CdS/ITO. The designed cell is formed without an organic hole transport layer (HTL) which, generally, harmfully affects the cell by causing stability issues. Next, we investigate the impact of the conduction band offset (CBO) between the electron transport layer (ETL) and the Sb2(S, Se)3 absorber utilizing the bandgap tunable material Cd1-xZnxS to achieve the optimum CBO. Various key design parameters for the presented cell such as the back contact work function as well as absorber thickness and doping concentration are also inspected. It is found that the most crucial parameter that affects the cell performance is the CBO which could be adjusted by modifying the Zn fraction in the ternary compound Cd1-xZnxS. Moreover, a study on the impact of the interface and bulk defects on device performance is carried out. The simulations, conducted in this study, are accomplished by SCAPS-1D simulator at 300 K temperature and under AM1.5G illumination.
Prospective efficiency boosting of full-inorganic single-junction Sb2(S, Se)3 solar cell
(Elsevier BV, 2022-09) Salem, Marwa S; Shaker, Ahmed; Almurayziq, Tariq S; Alshammari, Mohammad T
Antimony selenosulfide, Sb2(S, Se)3, is regarded as an appropriate absorber to be utilized in terrestrial single junction solar cell applications thanks to the tunability of its bandgap energy which could be adjusted around 1.3 eV. To enhance the power conversion efficiency (PCE) of Sb2(S, Se)3-based single junction solar cell, we propose some design recommendations by using device simulation. First, in order to validate the simulation model, a calibration step is accomplished by comparing the numerical simulation results with those of a fabricated cell structure consisting of Au/Sb2(S, Se)3/CdS/ITO. The designed cell is formed without an organic hole transport layer (HTL) which, generally, harmfully affects the cell by causing stability issues. Next, we investigate the impact of the conduction band offset (CBO) between the electron transport layer (ETL) and the Sb2(S, Se)3 absorber utilizing the bandgap tunable material Cd1-xZnxS to achieve the optimum CBO. Various key design parameters for the presented cell such as the back contact work function as well as absorber thickness and doping concentration are also inspected. It is found that the most crucial parameter that affects the cell performance is the CBO which could be adjusted by modifying the Zn fraction in the ternary compound Cd1-xZnxS. Moreover, a study on the impact of the interface and bulk defects on device performance is carried out. The simulations, conducted in this study, are accomplished by SCAPS-1D simulator at 300 K temperature and under AM1.5G illumination.