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Papers by Rafee Mahbub

International Journal of Photoenergy, 2017

Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar ... more Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar cells including various HTM layers such as spiro-OMeTAD, Cu 2 O, and CuSCN. ZnO nanorod array has been considered as an ETM layer. Device parameters such as thickness of the CH 3 NH 3 SnI 3 layer, defect density of interfaces, density of states, and metal work function were studied. For optimum parameters of all three structures, efficiency of 20.21%, 20.23%, and 18.34% has been achieved for spiro-OMeTAD, Cu 2 O, and CuSCN, respectively. From the simulations, an alternative lead-free perovskite solar cell is introduced with the CH 3 NH 3 SnI 3 absorber layer, ZnO nanorod ETM layer, and Cu 2 O HTM layer.

International Journal of Renewable Energy Research, 2017

Thin film CdS/CdTe solar cell is one of the leading technologies for providing high power conver... more Thin film CdS/CdTe solar cell is one of the leading technologies for providing high power conversion efficiency at comparatively low manufacturing cost. We have done modeling and simulation of thin film CdS/CdTe solar cell and then used nanowire CdS layer instead of planar CdS layer using SCAPS-1D to demonstrate the fact that the use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells by ~3%. The scattering cross section of CdS nanowire was observed using Lumerical FDTD solutions to determine that diameter of 40-60nm is preferable for CdS nanowires for using as window layer of CdS/CdTe solar cell . For thin film CdS/CdTe solar cell the open circuit voltage was 0.69V and efficiency was 15.42%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.82V and efficiency was 18.30%. Device parameters such as: temperature, interface state density, density of states, electron and hole mobility and metal work function were studied which can affect the effici...

Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive... more Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive Copper Indium Gallium Selenide (CIGS) absorber layer due to its high efficiency, low-cost, non-radioactive and environmental friendly behavior. Potential buffer layers for CZTS solar cells like ZnO, ZnS, In2S3 and ZnSe along with conventional CdS buffer layer are numerically analyzed. Among these structures, ZnS/CZTS structure shows an optimum efficiency of 26.82% (with Voc = 0.724 V, Jsc = 53.312 mA/cm 2 and fill factor = 69.44 %).This paper explicitly reveals the most favorable CZTS layer thickness around 2.5 μm, whereas buffer layer thickness lies just below 50 nm. Absorber carrier density has its effect on Voc and Jsc and so on efficiency. With increasing carrier density Jsc decreases while Voc increases. An optimum density of 5×10 17 cm to 1×10 cm shows a great result. The achieved results can lead to the development of higher efficiency CZTS thin film solar cells. (Avoid the words...

A continuous, static, and non-interfering water contaminant detection method is presented to meas... more A continuous, static, and non-interfering water contaminant detection method is presented to measure specific water contaminants (NaCl, MgCl2, and mixture of NaCl and MgCl2) using RF microwave principles. A coil is mounted on the surface of a glass tube and the liquid sample is placed inside of the tube. An external magnetic field generated by the coil continuously measures changes in radio frequency energy. The non-contact feature of the device allows a long sensor lifetime with high sensitivity for real-time measurements. The measurement parameter is reflection coefficient (S11) and the operating frequency is 10 MHz – 5 GHz. For NaCl and MgCl2, 11 different concentrations (1000 ppm – 400 ppb) liquid solutions are prepared. Amplitude changes and frequency shifts are noticeable among different materials and concentrations. Different test materials have different radio frequencies at which they undergo excitation and the responses are identified in S11 measurement. A machine learning algorithm is introduced to analyze the measured S11 data. A support vector regressor (SVR) model is trained using the measured data of various salt samples. The training data is constructed by concatenating the 20,000 amplitudes and 20,000 phase values from the measured S11 data. The hyperparameters of the SVR are optimized using 10-fold cross-validation method. Based on the trained model, the algorithm predicts the concentrations of the liquid samples. The experimental results indicate that the device can detect concentrations as low as 400 ppb with high accuracy.

Materials Science 2018, Atlanta, USA, 2018

Overview: A hybrid structure of Au/ZnO core-shell nanorod (NR) onto PbS quantum dot(QD) array is ... more Overview: A hybrid structure of Au/ZnO core-shell nanorod (NR) onto PbS quantum dot(QD) array is simulated for the power analysis of nanorods' size dependence of absorbed power using FDTD simulator Objective: Au/ZnO core-shell nanorod(NR) on an assembly of PbS quantum dot(QD) is proposed for light harvesting, nonlinear optics, and quantum information processing.

Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar ... more Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar cells including various HTM layers such as spiro-OMeTAD, Cu 2 O, and CuSCN. ZnO nanorod array has been considered as an ETM layer. Device parameters such as thickness of the CH 3 NH 3 SnI 3 layer, defect density of interfaces, density of states, and metal work function were studied. For optimum parameters of all three structures, efficiency of 20.21%, 20.23%, and 18.34% has been achieved for spiro-OMeTAD, Cu 2 O, and CuSCN, respectively. From the simulations, an alternative lead-free perovskite solar cell is introduced with the CH 3 NH 3 SnI 3 absorber layer, ZnO nanorod ETM layer, and Cu 2 O HTM layer.

– Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has b... more – Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has been analyzed using the Finite-Difference Time-Domain (FDTD) simulation. The source used in the simulation is a Total-Field Scattered-Field (TFSF) which ranged from 300-900 nm. Strong scattering cross section is observed from the versus wavelength (λ) curve. Increase in absorption cross section is also observed due to GaAs and AlGaAs having direct bandgaps. For core radii of 25 nm, 35 nm and 45 nm increases respectively. The increase in thickness of AlGaAs layer elevated the scattering cross section far greater than the increase in thickness of the Au layer and the joint increase in thickness of the Au/AlGaAs layer increases the spectral linewidth. Shifts in wavelength (λ) is also observed as the radius of the core-multishell NW increases. Such high optical scattering properties can be used in infra-red lasing operations. Since there is a surface passivation of AlGaAs, the core multi-shell NW is also useful as photodetectors

Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive... more Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive Copper Indium Gallium
Selenide (CIGS) absorber layer due to its high efficiency, low-cost, non-radioactive and environmental friendly behavior.
Potential buffer layers for CZTS solar cells like ZnO, ZnS, In2S3 and ZnSe along with conventional CdS buffer layer are
numerically analyzed. Among these structures, ZnS/CZTS structure shows an optimum efficiency of 26.82% (with Voc = 0.724 V,
Jsc = 53.312 mA/cm2 and fill factor = 69.44 %).This paper explicitly reveals the most favorable CZTS layer thickness around 2.5
μm, whereas buffer layer thickness lies just below 50 nm. Absorber carrier density has its effect on Voc and Jsc and so on
efficiency. With increasing carrier density Jsc decreases while Voc increases. An optimum density of 5×1017 cm-3 to 1×1018 cm-3
shows a great result. The achieved results can lead to the development of higher efficiency CZTS thin film solar cells.
(Avoid the words in abstract Ex. Recently in this work research)

Thin film CdS/CdTe solar cells has become one of the leading technologies for providing high powe... more Thin film CdS/CdTe solar cells has become one of the leading technologies for providing high power conversion efficiency at comparatively low manufacturing cost. We have done modeling and simulation of thin film CdS/CdTe solar cell and then used nanowire CdS layer instead of planar CdS layer using SCAPS-1D to demonstrate the fact that the use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells by ~3%. The scattering cross section of CdS nanowire was observed using Lumerical FDTD solutions to determine the preferable diameter for CdS nanowires. For thin film CdS/CdTe solar cell the open circuit voltage was 0.69V and efficiency was 15.42%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.82V and efficiency was 18.30%. Device parameters such as: temperature, parasitic series and shunt resistance interface state density, density of states, electron and hole mobility and metal work function were studied which can affect the efficiency of the nanowire-CdS/CdTe solar cell. The rollover effect on nanowire CdS/CdTe solar cell was explained by varying the majority carrier barrier height of back contact from 0.4 to 0.7 eV. This indicates that when the barrier height is increased, a roll over effect occurs and the efficiency decreases.

Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has bee... more Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has been analyzed using the Finite-Difference Time-Domain (FDTD) simulation. The source used in the simulation is a Total-Field Scattered-Field (TFSF) which ranged from 300-900 nm. Strong scattering cross section (σ_scat) is observed from the σ_scat versus wavelength (λ) curve. Increase in absorption cross section is also observed due to Gallium Arsenide (GaAs) and Aluminium Gallium Arsenide (AlGaAs) having direct bandgaps. For core radii of 25 nm, 35 nm and 45 nm σ_scat increases respectively. The increase in thickness of AlGaAs layer elevated the scattering cross section far greater than the increase in thickness of the Au layer and the joint increase in thickness of the Au/AlGaAs layer increases the spectral linewidth. Shifts in wavelength (λ) is also observed as the radius of the core-multishell NW increases. Such high optical scattering properties can be used in infra-red lasing operations. Since there is a surface passivation of AlGaAs, the core multi-shell NW is also useful as photodetectors.

Conference Presentations by Rafee Mahbub

Thesis Chapters by Rafee Mahbub

A continuous, static, and non-interfering water contaminant detection method is presented to meas... more A continuous, static, and non-interfering water contaminant detection method is presented to measure specific water contaminants (NaCl, MgCl2, and mixture of NaCl and MgCl2) using RF microwave principles. A coil is mounted on the surface of a glass tube and the liquid sample is placed inside of the tube. An external magnetic field generated by the coil continuously measures changes in radio frequency energy. The non-contact feature of the device allows a long sensor lifetime with high sensitivity for real-time measurements. The measurement parameter is reflection coefficient (S11) and the operating frequency is 10 MHz – 5 GHz. For NaCl and MgCl2, 11 different concentrations (1000 ppm – 400 ppb) liquid solutions are prepared. Amplitude changes and frequency shifts are noticeable among different materials and concentrations. Different test materials have different radio frequencies at which they undergo excitation and the responses are identified in S11 measurement. A machine learning algorithm is introduced to analyze the measured S11 data. A support vector regressor (SVR) model is trained using the measured data of various salt samples. The training data is constructed by concatenating the 20,000 amplitudes and 20,000 phase values from the measured S11 data. The hyperparameters of the SVR are optimized using 10-fold cross-validation method. Based on the trained model, the algorithm predicts the concentrations of the liquid samples. The experimental results indicate that the device can detect concentrations as low as 400 ppb with high accuracy.

International Journal of Photoenergy, 2017

Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar ... more Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar cells including various HTM layers such as spiro-OMeTAD, Cu 2 O, and CuSCN. ZnO nanorod array has been considered as an ETM layer. Device parameters such as thickness of the CH 3 NH 3 SnI 3 layer, defect density of interfaces, density of states, and metal work function were studied. For optimum parameters of all three structures, efficiency of 20.21%, 20.23%, and 18.34% has been achieved for spiro-OMeTAD, Cu 2 O, and CuSCN, respectively. From the simulations, an alternative lead-free perovskite solar cell is introduced with the CH 3 NH 3 SnI 3 absorber layer, ZnO nanorod ETM layer, and Cu 2 O HTM layer.

International Journal of Renewable Energy Research, 2017

Thin film CdS/CdTe solar cell is one of the leading technologies for providing high power conver... more Thin film CdS/CdTe solar cell is one of the leading technologies for providing high power conversion efficiency at comparatively low manufacturing cost. We have done modeling and simulation of thin film CdS/CdTe solar cell and then used nanowire CdS layer instead of planar CdS layer using SCAPS-1D to demonstrate the fact that the use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells by ~3%. The scattering cross section of CdS nanowire was observed using Lumerical FDTD solutions to determine that diameter of 40-60nm is preferable for CdS nanowires for using as window layer of CdS/CdTe solar cell . For thin film CdS/CdTe solar cell the open circuit voltage was 0.69V and efficiency was 15.42%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.82V and efficiency was 18.30%. Device parameters such as: temperature, interface state density, density of states, electron and hole mobility and metal work function were studied which can affect the effici...

Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive... more Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive Copper Indium Gallium Selenide (CIGS) absorber layer due to its high efficiency, low-cost, non-radioactive and environmental friendly behavior. Potential buffer layers for CZTS solar cells like ZnO, ZnS, In2S3 and ZnSe along with conventional CdS buffer layer are numerically analyzed. Among these structures, ZnS/CZTS structure shows an optimum efficiency of 26.82% (with Voc = 0.724 V, Jsc = 53.312 mA/cm 2 and fill factor = 69.44 %).This paper explicitly reveals the most favorable CZTS layer thickness around 2.5 μm, whereas buffer layer thickness lies just below 50 nm. Absorber carrier density has its effect on Voc and Jsc and so on efficiency. With increasing carrier density Jsc decreases while Voc increases. An optimum density of 5×10 17 cm to 1×10 cm shows a great result. The achieved results can lead to the development of higher efficiency CZTS thin film solar cells. (Avoid the words...

A continuous, static, and non-interfering water contaminant detection method is presented to meas... more A continuous, static, and non-interfering water contaminant detection method is presented to measure specific water contaminants (NaCl, MgCl2, and mixture of NaCl and MgCl2) using RF microwave principles. A coil is mounted on the surface of a glass tube and the liquid sample is placed inside of the tube. An external magnetic field generated by the coil continuously measures changes in radio frequency energy. The non-contact feature of the device allows a long sensor lifetime with high sensitivity for real-time measurements. The measurement parameter is reflection coefficient (S11) and the operating frequency is 10 MHz – 5 GHz. For NaCl and MgCl2, 11 different concentrations (1000 ppm – 400 ppb) liquid solutions are prepared. Amplitude changes and frequency shifts are noticeable among different materials and concentrations. Different test materials have different radio frequencies at which they undergo excitation and the responses are identified in S11 measurement. A machine learning algorithm is introduced to analyze the measured S11 data. A support vector regressor (SVR) model is trained using the measured data of various salt samples. The training data is constructed by concatenating the 20,000 amplitudes and 20,000 phase values from the measured S11 data. The hyperparameters of the SVR are optimized using 10-fold cross-validation method. Based on the trained model, the algorithm predicts the concentrations of the liquid samples. The experimental results indicate that the device can detect concentrations as low as 400 ppb with high accuracy.

Materials Science 2018, Atlanta, USA, 2018

Overview: A hybrid structure of Au/ZnO core-shell nanorod (NR) onto PbS quantum dot(QD) array is ... more Overview: A hybrid structure of Au/ZnO core-shell nanorod (NR) onto PbS quantum dot(QD) array is simulated for the power analysis of nanorods' size dependence of absorbed power using FDTD simulator Objective: Au/ZnO core-shell nanorod(NR) on an assembly of PbS quantum dot(QD) is proposed for light harvesting, nonlinear optics, and quantum information processing.

Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar ... more Simulation has been done using SCAPS-1D to examine the efficiency of CH 3 NH 3 SnI 3-based solar cells including various HTM layers such as spiro-OMeTAD, Cu 2 O, and CuSCN. ZnO nanorod array has been considered as an ETM layer. Device parameters such as thickness of the CH 3 NH 3 SnI 3 layer, defect density of interfaces, density of states, and metal work function were studied. For optimum parameters of all three structures, efficiency of 20.21%, 20.23%, and 18.34% has been achieved for spiro-OMeTAD, Cu 2 O, and CuSCN, respectively. From the simulations, an alternative lead-free perovskite solar cell is introduced with the CH 3 NH 3 SnI 3 absorber layer, ZnO nanorod ETM layer, and Cu 2 O HTM layer.

– Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has b... more – Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has been analyzed using the Finite-Difference Time-Domain (FDTD) simulation. The source used in the simulation is a Total-Field Scattered-Field (TFSF) which ranged from 300-900 nm. Strong scattering cross section is observed from the versus wavelength (λ) curve. Increase in absorption cross section is also observed due to GaAs and AlGaAs having direct bandgaps. For core radii of 25 nm, 35 nm and 45 nm increases respectively. The increase in thickness of AlGaAs layer elevated the scattering cross section far greater than the increase in thickness of the Au layer and the joint increase in thickness of the Au/AlGaAs layer increases the spectral linewidth. Shifts in wavelength (λ) is also observed as the radius of the core-multishell NW increases. Such high optical scattering properties can be used in infra-red lasing operations. Since there is a surface passivation of AlGaAs, the core multi-shell NW is also useful as photodetectors

Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive... more Cu2ZnSnS4 (CZTS) absorber layer research shows extensive influential factors to replace expensive Copper Indium Gallium
Selenide (CIGS) absorber layer due to its high efficiency, low-cost, non-radioactive and environmental friendly behavior.
Potential buffer layers for CZTS solar cells like ZnO, ZnS, In2S3 and ZnSe along with conventional CdS buffer layer are
numerically analyzed. Among these structures, ZnS/CZTS structure shows an optimum efficiency of 26.82% (with Voc = 0.724 V,
Jsc = 53.312 mA/cm2 and fill factor = 69.44 %).This paper explicitly reveals the most favorable CZTS layer thickness around 2.5
μm, whereas buffer layer thickness lies just below 50 nm. Absorber carrier density has its effect on Voc and Jsc and so on
efficiency. With increasing carrier density Jsc decreases while Voc increases. An optimum density of 5×1017 cm-3 to 1×1018 cm-3
shows a great result. The achieved results can lead to the development of higher efficiency CZTS thin film solar cells.
(Avoid the words in abstract Ex. Recently in this work research)

Thin film CdS/CdTe solar cells has become one of the leading technologies for providing high powe... more Thin film CdS/CdTe solar cells has become one of the leading technologies for providing high power conversion efficiency at comparatively low manufacturing cost. We have done modeling and simulation of thin film CdS/CdTe solar cell and then used nanowire CdS layer instead of planar CdS layer using SCAPS-1D to demonstrate the fact that the use of CdS nanowires enhances the efficiency of the CdS/CdTe solar cells by ~3%. The scattering cross section of CdS nanowire was observed using Lumerical FDTD solutions to determine the preferable diameter for CdS nanowires. For thin film CdS/CdTe solar cell the open circuit voltage was 0.69V and efficiency was 15.42%. For nanowire CdS/CdTe solar cell model the open circuit voltage was 0.82V and efficiency was 18.30%. Device parameters such as: temperature, parasitic series and shunt resistance interface state density, density of states, electron and hole mobility and metal work function were studied which can affect the efficiency of the nanowire-CdS/CdTe solar cell. The rollover effect on nanowire CdS/CdTe solar cell was explained by varying the majority carrier barrier height of back contact from 0.4 to 0.7 eV. This indicates that when the barrier height is increased, a roll over effect occurs and the efficiency decreases.

Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has bee... more Absorption and Scattering cross section of Au/AlGaAs/GaAs single core-multishell nanowire has been analyzed using the Finite-Difference Time-Domain (FDTD) simulation. The source used in the simulation is a Total-Field Scattered-Field (TFSF) which ranged from 300-900 nm. Strong scattering cross section (σ_scat) is observed from the σ_scat versus wavelength (λ) curve. Increase in absorption cross section is also observed due to Gallium Arsenide (GaAs) and Aluminium Gallium Arsenide (AlGaAs) having direct bandgaps. For core radii of 25 nm, 35 nm and 45 nm σ_scat increases respectively. The increase in thickness of AlGaAs layer elevated the scattering cross section far greater than the increase in thickness of the Au layer and the joint increase in thickness of the Au/AlGaAs layer increases the spectral linewidth. Shifts in wavelength (λ) is also observed as the radius of the core-multishell NW increases. Such high optical scattering properties can be used in infra-red lasing operations. Since there is a surface passivation of AlGaAs, the core multi-shell NW is also useful as photodetectors.

A continuous, static, and non-interfering water contaminant detection method is presented to meas... more A continuous, static, and non-interfering water contaminant detection method is presented to measure specific water contaminants (NaCl, MgCl2, and mixture of NaCl and MgCl2) using RF microwave principles. A coil is mounted on the surface of a glass tube and the liquid sample is placed inside of the tube. An external magnetic field generated by the coil continuously measures changes in radio frequency energy. The non-contact feature of the device allows a long sensor lifetime with high sensitivity for real-time measurements. The measurement parameter is reflection coefficient (S11) and the operating frequency is 10 MHz – 5 GHz. For NaCl and MgCl2, 11 different concentrations (1000 ppm – 400 ppb) liquid solutions are prepared. Amplitude changes and frequency shifts are noticeable among different materials and concentrations. Different test materials have different radio frequencies at which they undergo excitation and the responses are identified in S11 measurement. A machine learning algorithm is introduced to analyze the measured S11 data. A support vector regressor (SVR) model is trained using the measured data of various salt samples. The training data is constructed by concatenating the 20,000 amplitudes and 20,000 phase values from the measured S11 data. The hyperparameters of the SVR are optimized using 10-fold cross-validation method. Based on the trained model, the algorithm predicts the concentrations of the liquid samples. The experimental results indicate that the device can detect concentrations as low as 400 ppb with high accuracy.