Abdelrahman M. Askar

Abdelrahman M. Askar

Simon Fraser University

H-index: 17

North America-Canada

About Abdelrahman M. Askar

Abdelrahman M. Askar, With an exceptional h-index of 17 and a recent h-index of 15 (since 2020), a distinguished researcher at Simon Fraser University, specializes in the field of 2D materials, Nanoelectronics, High-frequency diodes, Photovoltaics, Perovskite.

His recent articles reflect a diverse array of research interests and contributions to the field:

Isolated Iridium Sites on Potassium‐Doped Carbon‐nitride wrapped Tellurium Nanostructures for Enhanced Glycerol Photooxidation

Two-dimensional tellurium-based diodes for RF applications

Unique Photoactivated Time‐Resolved Response in 2D GeS for Selective Detection of Volatile Organic Compounds (Adv. Sci. 10/2023)

Flexible High‐Performance Photovoltaic Devices based on 2D MoS2 Diodes with Geometrically Asymmetric Contact Areas

Self-powered, broadband photodetector based on two-dimensional tellurium-silicon heterojunction

Instability of dye-sensitized solar cells using natural dyes and approaches to improving stability–an overview

Inhibition of amine–water proton exchange stabilizes perovskite ink for scalable solar cell fabrication

Bismuth Stabilizes the α-Phase of Formamidinium Lead Iodide Perovskite Single Crystals

Abdelrahman M. Askar Information

University

Simon Fraser University

Position

PhD Student

Citations(all)

925

Citations(since 2020)

751

Cited By

468

hIndex(all)

17

hIndex(since 2020)

15

i10Index(all)

21

i10Index(since 2020)

19

Email

University Profile Page

Simon Fraser University

Abdelrahman M. Askar Skills & Research Interests

2D materials

Nanoelectronics

High-frequency diodes

Photovoltaics

Perovskite

Top articles of Abdelrahman M. Askar

Isolated Iridium Sites on Potassium‐Doped Carbon‐nitride wrapped Tellurium Nanostructures for Enhanced Glycerol Photooxidation

Authors

Pawan Kumar,Abdelrahman Askar,Jiu Wang,Soumyabrata Roy,Srinivasu Kancharlapalli,Xiyang Wang,Varad Joshi,Hangtian Hu,Karthick Kannimuthu,Dhwanil Trivedi,Praveen Bollini,Yimin A Wu,Pulickel M Ajayan,Michael M Adachi,Jinguang Hu,Md Golam Kibria

Journal

Advanced Functional Materials

Published Date

2024/3/19

Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by‐product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium‐doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible‐NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core‐shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of …

Two-dimensional tellurium-based diodes for RF applications

Authors

Abdelrahman M Askar,Paula Palacios,Francisco Pasadas,Mohamed Saeed,Mohammad Reza Mohammadzadeh,Renato Negra,Michael M Adachi

Journal

npj 2D Materials and Applications

Published Date

2023/9/27

The research of two-dimensional (2D) Tellurium (Te) or tellurene is thriving to address current challenges in emerging thin-film electronic and optoelectronic devices. However, the study of 2D-Te-based devices for high-frequency applications is still lacking in the literature. This work presents a comprehensive study of two types of radio frequency (RF) diodes based on 2D-Te flakes and exploits their distinct properties in two RF applications. First, a metal-insulator-semiconductor (MIS) structure is employed as a nonlinear device in a passive RF mixer, where the achieved conversion loss at 2.5 GHz and 5 GHz is as low as 24 dB and 29 dB, respectively. Then, a metal-semiconductor (MS) diode is tested as a zero-bias millimeter-wave power detector and reaches an outstanding linear-in-dB dynamic range over 40 dB, while having voltage responsivities as high as 257 V ⋅ W−1 at 1 GHz (up to 1 V detected output …

Unique Photoactivated Time‐Resolved Response in 2D GeS for Selective Detection of Volatile Organic Compounds (Adv. Sci. 10/2023)

Authors

Mohammad Reza Mohammadzadeh,Amirhossein Hasani,Keyvan Jaferzadeh,Mirette Fawzy,Thushani De Silva,Amin Abnavi,Ribwar Ahmadi,Hamidreza Ghanbari,Abdelrahman Askar,Fahmid Kabir,RKND Rajapakse,Michael M Adachi

Journal

Advanced Science

Published Date

2023/4

In article number 2205458, Michael M. Adachi and co-workers demonstrate a new sensing mechanism based on surface interactions between volatile organic compounds (VOC) and UV-excited twodimensional (2D) germanium sulfide (GeS), which provides an effective solution to distinguish VOCs. The GeS sensor shows a unique dynamic response to different VOC species, facilitating identification and qualitative measurement of VOCs. Machine learning is utilized to distinguish VOC species from their dynamic response via visualization with high accuracy. The proposed approach demonstrates the potential of 2D GeS as a promising candidate for selective VOCs sensors in critical applications such as non-invasive diagnosis of diseases and health monitoring.

Flexible High‐Performance Photovoltaic Devices based on 2D MoS2 Diodes with Geometrically Asymmetric Contact Areas

Authors

Amin Abnavi,Ribwar Ahmadi,Hamidreza Ghanbari,Mirette Fawzy,Amirhossein Hasani,Thushani De Silva,Abdelrahman M Askar,Mohammad Reza Mohammadzadeh,Fahmid Kabir,Michael Whitwick,Mario Beaudoin,Stephen K O'Leary,Michael M Adachi

Journal

Advanced Functional Materials

Published Date

2023/2

Optoelectronic performance of 2D transition metal dichalcogenides (TMDs)‐based solar cells and self‐powered photodetectors remain limited due to fabrication challenges, such as difficulty in doping TMDs to form p–n junctions. Herein, MoS2 diodes based on geometrically asymmetric contact areas are shown to achieve a high current rectification ratio of ≈105, facilitating efficient photovoltaic charge collection. Under solar illumination, the device demonstrates a high open‐circuit voltage (Voc) of 430 mV and a short‐circuit current density (Jsc) of −13.42 mA cm−2, resulting in a high photovoltaic power conversion efficiency (PCE) of 3.16%, the highest reported for a lateral 2D solar cell. The diodes also show a high photoresponsivity of 490.3 mA W−1, and a large photo detectivity of 4.05 × 1010 Jones, along with a fast response time of 0.8 ms under 450 nm wavelength at zero bias for self‐powered …

Self-powered, broadband photodetector based on two-dimensional tellurium-silicon heterojunction

Authors

Amirhossein Hasani,Mohammad Reza Mohammadzadeh,Hamidreza Ghanbari,Mirette Fawzy,Thushani De Silva,Amin Abnavi,Ribwar Ahmadi,Abdelrahman M Askar,Fahmid Kabir,RKND Rajapakse,Michael M Adachi

Journal

ACS omega

Published Date

2022/12/13

As a new class of two-dimensional (2D) materials and a group-VI chalcogen, tellurium (Te) has emerged as a p-type semiconductor with high carrier mobility. Potential applications include high-speed opto-electronic devices for communication. One method to enhance the performance of 2D material-based photodetectors is by integration with a IV group of semiconductors such as silicon (Si). In this work, we demonstrate a self-powered, high-speed, broadband photodetector based on the 2D Te/n-type Si heterojunction. The fabricated Te/n-type Si heterojunction exhibits high performance in the UV–vis–NIR light with a high responsivity of up to ∼250 mA/W and a photocurrent-to-dark current ratio (Ion/Ioff) of ∼106, fast response time of 8.6 μs, and superior repeatability and stability. The results show that the fabricated Te/n-type Si heterojunction photodetector has a strong potential to be utilized in ultrafast …

Instability of dye-sensitized solar cells using natural dyes and approaches to improving stability–an overview

Authors

Fahmid Kabir,Serajum Manir,Md Mossaraf Hossain Bhuiyan,Sikandar Aftab,Hamidreza Ghanbari,Amirhossein Hasani,Mirette Fawzy,GL Thushani De Silva,Mohammad Reza Mohammadzadeh,Ribwar Ahmadi,Amin Abnavi,Abdelrahman M Askar,Michael M Adachi

Published Date

2022/8/1

Natural dye-based dye-sensitized solar cells (DSSCs) have attracted considerable attention due to their eco-friendly production, low-cost manufacturing methodologies, and competitive efficiency. However, the lack of long-term stability of the cell limits the use of natural dye-based DSSCs. This review article focuses on different reasons for the instability of natural dye-based DSSCs. For a comprehensive study, cell instability of natural dye-based DSSC is divided into physical (effect of temperature, UV illumination, and humidity) and chemical instabilities (degradation of dye sensitizer, electrolyte, and counter electrode, and effect of temperature, radiation, water, and oxygen). Finally, different mechanisms to increase cell stability (UV filter, sealant, development of electrolyte, and counter electrode) are presented. This article panoramically reviews the natural dye-based DSSCs instability and additional stability …

Inhibition of amine–water proton exchange stabilizes perovskite ink for scalable solar cell fabrication

Authors

Erin G Moloney,Deepak Thrithamarassery Gangadharan,Vishal Yeddu,Dongyang Zhang,Shahram Moradi,Abdelrahman M Askar,Michael M Adachi,David C Leitch,Makhsud I Saidaminov

Journal

Chemistry of Materials

Published Date

2022/5/3

Ambient air processing is desirable for the industrial fabrication of perovskite solar cells. Here, we show that perovskite ink containing methylammonium and formamidinium in N-methyl-2-pyrrolidone and N,N-dimethylformamide, a cosolvent composition that satisfies prerequisites for upscaling solar cell fabrication, degrades within a day in ambient air. From 1H NMR spectroscopic analysis, we find that water proton exchange with methylammonium and formamidinium facilitates the aminolysis of formamidinium by methylamine. The addition of elemental sulfur inhibits this proton exchange process via sulfur–amine reactions, resulting in a stable perovskite ink with an extrapolated half-life of 6300 h. The control ink aged for 1 day does not form perovskite films for solar cell fabrication, while the sulfur-stabilized ink is reproducibly used to make devices with efficiencies >15% when aged for over 1 month. The stabilized …

Bismuth Stabilizes the α-Phase of Formamidinium Lead Iodide Perovskite Single Crystals

Authors

Soumya Kundu,Dongyang Zhang,Abdelrahman M Askar,Erin G Moloney,Michael M Adachi,Ayesha Nadeem,Shahram Moradi,Vishal Yeddu,Ahmed L Abdelhady,Oleksandr Voznyy,Makhsud I Saidaminov

Journal

ACS Materials Letters

Published Date

2022/3/16

α-FAPbI3 (FA = formamidinium) perovskite offers an optimal bandgap for single-junction solar cells but converts into a more thermodynamically stable photoinactive δ-polymorph at room temperature. FA- or I-site substitutional alloying stabilizes α-FAPbI3; however, it leads to compositional segregation in operational devices. Here, we stabilize α-FAPbI3 single crystals through Pb-site doping with a heterovalent metal–bismuth (Bi). We show that undoped α-FAPbI3 has an α- to δ-phase half-life transition of <0.15 h, while the optimum concentration of Bi extends it by 4 orders of magnitude. Differential scanning calorimetry (DSC) reveals that Bi has effectively decreased the δ- to α-phase onset transition temperature. Density functional theory (DFT) calculations suggest a relatively clean gap, supporting previous findings on the improved photovoltaic performance of Bi-doped α-FAPbI3-based solar cells.

Ultrasensitive rapid cytokine sensors based on asymmetric geometry two-dimensional MoS2 diodes

Authors

Thushani De Silva,Mirette Fawzy,Amirhossein Hasani,Hamidreza Ghanbari,Amin Abnavi,Abdelrahman Askar,Yue Ling,Mohammad Reza Mohammadzadeh,Fahmid Kabir,Ribwar Ahmadi,Miriam Rosin,Karen L Kavanagh,Michael M Adachi

Journal

Nature communications

Published Date

2022/12/19

The elevation of cytokine levels in body fluids has been associated with numerous health conditions. The detection of these cytokine biomarkers at low concentrations may help clinicians diagnose diseases at an early stage. Here, we report an asymmetric geometry MoS2 diode-based biosensor for rapid, label-free, highly sensitive, and specific detection of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine. This sensor is functionalized with TNF-α binding aptamers to detect TNF-α at concentrations as low as 10 fM, well below the typical concentrations found in healthy blood. Interactions between aptamers and TNF-α at the sensor surface induce a change in surface energy that alters the current-voltage rectification behavior of the MoS2 diode, which can be read out using a two-electrode configuration. The key advantages of this diode sensor are the simple fabrication process and electrical readout, and …

Thickness-modulated lateral MoS 2 diodes with sub-terahertz cutoff frequency

Authors

Abdelrahman M Askar,Mohamed Saeed,Ahmed Hamed,Renato Negra,Michael M Adachi

Journal

Nanoscale

Published Date

2021

Thickness-modulated lateral MoS2 diodes with an extracted benchmark cutoff frequency (fc) of up to 126 GHz are implemented and fully characterised. Fabricated diodes demonstrate an on–off current ratio of more than 600 and a short circuit current responsivity at zero-bias of 7 A/W. The excellent performance achieved in our device is attributed to reduced contact resistance from using In/Au contacts and low junction capacitance due to the lateral device structure. In addition, the use of multilayer MoS2 crystals enabled relatively high current flow. Small- and large-signal models are extracted from DC and RF characterisation of the fabricated diode prototype. Extracted compact models are compared to the measured DC and S-parameters of the diode, demonstrating excellent matching between models and measurements. The presented diode is suitable for switching circuits and high frequency applications.

Investigating the Tetragonal‐to‐Orthorhombic Phase Transition of Methylammonium Lead Iodide Single Crystals by Detailed Photoluminescence Analysis

Authors

Konstantin Schötz,Abdelrahman M Askar,Anna Köhler,Karthik Shankar,Fabian Panzer

Journal

Advanced Optical Materials

Published Date

2020/9

Here, the phase‐transition from tetragonal to orthorhombic crystal structure of the halide perovskite methylammonium lead iodide single crystal is investigated. Temperature dependent photoluminescence (PL) measurements in the temperature range between 165 and 100 K show complex PL spectra where in total five different PL peaks can be identified. All observed PL features can be assigned to different optical effects from the two crystal phases using detailed PL analyses. This allows to quantify the fraction of tetragonal phase that still occurs below the phase transition temperature. It is found that at 150 K, 0.015% tetragonal phase remain, and PL signatures are observed from quantum confined tetragonal domains, suggesting their size to be about 7–15 nm down to 120 K. The tetragonal inclusions also exhibit an increased Urbach Energy, implying a high degree of structural disorder. The results first illustrate …

Phase Evolution in Methylammonium Tin Halide Perovskites with Variable Temperature Solid-State 119Sn NMR Spectroscopy

Authors

Michelle Ha,Abhoy Karmakar,Guy M Bernard,Enoc Basilio,Arun Krishnamurthy,Abdelrahman M Askar,Karthik Shankar,Scott Kroeker,Vladimir K Michaelis

Journal

The Journal of Physical Chemistry C

Published Date

2020/6/17

Hybrid organic–inorganic metal-halide perovskite materials are an emerging class of materials that could profoundly change the optoelectronic and solar absorber research fields and have far-reaching applications. Unfortunately, the leading solar-absorbing candidates are lead-containing materials and suffer from chemical instability, eventually decomposing, resulting in detrimental long-term environmental concerns. A series of nontoxic group 14 Sn(II)-based hybrid organic–inorganic metal-halide perovskites is investigated using variable-temperature solid-state nuclear magnetic resonance (NMR) spectroscopy to examine their unique phases that appear between 150 and 540 K. Each phase of the MASnX3 (MA+ = CH3NH3+ and X– = Cl–, Br–, or I–) series is identified and compared to results from quantum chemical calculations of anionic polyhedron clusters. The analysis of the polyhedra about the Sn center is …

Double peak emission in lead halide perovskites by self-absorption

Authors

Konstantin Schötz,Abdelrahman M Askar,Wei Peng,Dominik Seeberger,Tanaji P Gujar,Mukundan Thelakkat,Anna Köhler,Sven Huettner,Osman M Bakr,Karthik Shankar,Fabian Panzer

Journal

Journal of Materials Chemistry C

Published Date

2020

Despite the rapidly increasing efficiencies of perovskite solar cells, the optoelectronic properties of this material class are not completely understood. Especially when measured photoluminescence (PL) spectra consist of multiple peaks, their origin is still debated. In this work, we investigate in detail double peak PL spectra of halide perovskite thin films and single crystals with different material compositions. By different optical spectroscopic approaches and quantitative models, we demonstrate that the additional PL peak results from an extensive self-absorption effect, whose impact is intensified by strong internal reflections. This self-absorption accounts for the unusual temperature dependence of the additional PL peak and it implies that absorption until far into the perovskite's Urbach tail is important. The internal reflections entail that even for thin films self-absorption can have a significant contribution to the PL …

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Abdelrahman M. Askar FAQs

What is Abdelrahman M. Askar's h-index at Simon Fraser University?

The h-index of Abdelrahman M. Askar has been 15 since 2020 and 17 in total.

What are Abdelrahman M. Askar's top articles?

The articles with the titles of

Isolated Iridium Sites on Potassium‐Doped Carbon‐nitride wrapped Tellurium Nanostructures for Enhanced Glycerol Photooxidation

Two-dimensional tellurium-based diodes for RF applications

Unique Photoactivated Time‐Resolved Response in 2D GeS for Selective Detection of Volatile Organic Compounds (Adv. Sci. 10/2023)

Flexible High‐Performance Photovoltaic Devices based on 2D MoS2 Diodes with Geometrically Asymmetric Contact Areas

Self-powered, broadband photodetector based on two-dimensional tellurium-silicon heterojunction

Instability of dye-sensitized solar cells using natural dyes and approaches to improving stability–an overview

Inhibition of amine–water proton exchange stabilizes perovskite ink for scalable solar cell fabrication

Bismuth Stabilizes the α-Phase of Formamidinium Lead Iodide Perovskite Single Crystals

...

are the top articles of Abdelrahman M. Askar at Simon Fraser University.

What are Abdelrahman M. Askar's research interests?

The research interests of Abdelrahman M. Askar are: 2D materials, Nanoelectronics, High-frequency diodes, Photovoltaics, Perovskite

What is Abdelrahman M. Askar's total number of citations?

Abdelrahman M. Askar has 925 citations in total.

What are the co-authors of Abdelrahman M. Askar?

The co-authors of Abdelrahman M. Askar are Michael M Adachi.

    Co-Authors

    H-index: 18
    Michael M Adachi

    Michael M Adachi

    Simon Fraser University

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