Riku Chowdhury

Upscaling laboratory organic electronic sensor devices to roll-to-roll printing: The effect of printable electrodes on device operation

Applied physics letters, Apr 22, 2024

Effects of concentration profile on charge injection in continuously graded mixed-host organic light emitting diode

Thin Solid Films, Nov 1, 2016

Although the mixed-host organic light emitting diode (OLED) has been known for improved performan... more Although the mixed-host organic light emitting diode (OLED) has been known for improved performance, the charge injection and mobility may not be uniform in the light emitting layer (EML) hence affecting the exciton formation and recombination. In this work, we investigate the effects of concentration profiles of electron-and hole-transport materials in EML on the charge injection and confinement as a result of in-situ formation of transport layers by thermal evaporation of a pre-mixed source. Experimental results show that the OLED performance depends on the continuously graded concentration profiles, and are correlated to numerical simulations which reveal charge confinement, spatial shift of recombination zone and lowering of hole mobility.

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Numerical and experimental studies of mixed-host organic light emitting diodes

Current Applied Physics, Nov 1, 2015

Abstract Electrical characteristic and luminance of three mixed-host organic light emitting diode... more Abstract Electrical characteristic and luminance of three mixed-host organic light emitting diodes (OLEDs): namely the uniformly mixed, step-wise graded and mixed, and continuously graded and mixed, were compared with the conventional hetero-junction OLED in both numerical and experimental studies. These mixed-host OLEDs were fabricated by a mixed-source thermal evaporation process, and half-cell devices were also fabricated to provide some input parameters for OLED simulations. The current efficiencies were largely influenced by their device structures and strongly agreed with the computed current balance factors. The improved mixed-host OLED performances can be discussed with aid from simulations, which include spatial distributions of electron and hole, carrier mobility, electric field profiles, the total recombination rates in the light emitting layer.

Effect of higher carrier injection rate on charge transport and recombination in mixed-host organic light emitting diode

The effect of anode surface modification on performance of uniformly mixed-host (MH) emissive lay... more The effect of anode surface modification on performance of uniformly mixed-host (MH) emissive layer (EML) based organic light emitting diode (OLED) has been investigated by the numerical simulation. Indium Tin Oxide (ITO) used as anode in the device. Due to proposed surface modification technique of ITO, the energy barrier at anode/organic layer interface is reduced which consummately enhanced the hole injection rate that leads to balance of carriers transportation and recombination in the EML. Through the numerical simulation, the electrical characteristics and internal device physics of uniform MH-OLED have been analyzed quantitatively. Calculated current balance factor which is related to the external quantum efficiency also confirmed the efficiency enhancement of MH-OLED by the proposed ITO work function modification technique.

Matlab simscape simulation of an open voltage algorithm based maximum power point tracker for battery charging PV system

ABSTRACT Currently, Photovoltaic (PV) energy is the most important energy resource in electrical ... more ABSTRACT Currently, Photovoltaic (PV) energy is the most important energy resource in electrical power applications around the world since it is inexhaustible, clean and pollution free. As the output power from the PV arrays changing with solar irradiance and temperature, so it is necessary to operate the photovoltaic (PV) system at the maximum power point (MPP) to increase the power extraction from the solar panel. For this effective operation and maximum power extraction from a PV system, Maximum power point tracking (MPPT) algorithm plays a vital role by operating the PV energy system near the MPP. In this work, amongst several existing well established MPPT algorithms, the open voltage (OV) based algorithm is chosen for simulation of a PV system using Matlab / Simscape. As maximum power point (MPP) can be attained with a certain amount of load from the PV power system, so load matching is an important concept of MPPT algorithms. Here, the performances of this open voltage (OV) based algorithm method is evaluated for different values of solar radiation and battery was used as load to see the charging performance for the algorithm.

A model for prediction of monthly solar radiation of different meterological locations of Bangladesh using aritficial neural network data mining tool

Solar energy generated by the sunlight is non schedulable due to the stochastic behavior of meteo... more Solar energy generated by the sunlight is non schedulable due to the stochastic behavior of meteorological conditions. Also the equipment for measuring the solar irradiance is expensive and rarely available in all locations of the globe. Hence prior knowledge of solar radiation is very important, for better management, sizing and control of solar energy installations. Predictive data mining such as Artificial Neural Network (ANN) is one of the most reliable and accurate model for forecasting solar radiation. There are a number of meteorological and geographical parameters which affect the solar radiation prediction model. So, identification of most influential parameters for better prediction accuracy is a crucial factor. In this paper, three attribute evaluators of Waikato Environment for Knowledge Analysis (WEKA) such as Classifier Subset Eval, CFS Subset Eval and Wrapper Subset Eval are used to select the most influential input parameters for ANN model for prediction of solar radiation in different meteorological locations of Bangladesh. Then the selected parameters are used to train, validate and test the ANN model. During the training process the number of hidden layer neuron are changed to find optimal network architecture. The prediction accuracy of the ANN models are evaluated using the statistical parameters such as Mean Absolute Percentage Error(MAPE), Mean Square Error(MSE) and goodness of fit(R). The simulated result shows that the subset selected by the Wrapper subset evaluator outperforms.

Electrical characteristics of two dimensionally modeled InGaN/InN/InGaN-based double channel HEMTs (DHEMTs)

In this paper, InGaN/InN/InGaN-based double channel HEMTs are investigated by numerical simulatio... more In this paper, InGaN/InN/InGaN-based double channel HEMTs are investigated by numerical simulation from the self-consistent solution of Schrodinger-Poisson systems. The influences of polarization charges and quantum effects are incorporated into this model. The simulation model predicts the two-dimensional electrical characteristics (internal electric fields and distribution of charges in the channel) that are associated with specified physical structures and bias conditions through the proper material parameters, the polarization field and surface states. Corresponding analysis and discussion based on the simulation results are subsequently given. This analysis provides a platform to investigate the InN-based double channel HEMTs and to optimize their design.

Surfactant Engineering and Its Role in Determining the Performance of Nanoparticulate Organic Photovoltaic Devices

ACS omega, Mar 9, 2022

The fabrication of organic photovoltaics (OPVs) from non-hazardous nanoparticulate (NP) inks offe... more The fabrication of organic photovoltaics (OPVs) from non-hazardous nanoparticulate (NP) inks offers considerable promise for the development of ecofriendly large-scale printed solar modules. However, the typical NP core−shell morphology (driven by the different donor/acceptor affinities for the surfactant used in NP synthesis) currently hinders the photovoltaic performance. As such, surfactant engineering offers an elegant approach to synthesizing a more optimal intermixed NP morphology and hence an improved photovoltaic performance. In this work, the morphology of conventional sodium dodecyl sulfate (SDS) and 2-(3-thienyl) ethyloxybutylsulfonate (TEBS)-stabilized poly(3-hexylthiophene) (P3HT) donor:phenyl-C 61-butyric acid methyl ester (PC 61 BM) acceptor NPs is probed using scanning transmission X-ray microscopy, UV−vis spectroscopy, grazing-incidence X-ray diffraction, and scanning electron microscopy. While the SDS-stabilized NPs exhibit a size-independent core−shell morphology, this work reveals that TEBS-stabilized NPs deliver an intermixed morphology, the extent of which depends on the particle size. Consequently, by optimizing the TEBS-stabilized NP size and distribution, NP-OPV devices with a power conversion efficiency that is ∼50% higher on average than that of the corresponding SDS-based NP-OPV devices are produced.

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Surfactant Engineering and Its Role in Determining the Performance of Nanoparticulate Organic Photovoltaic Devices

The fabrication of organic photovoltaics (OPVs) from non-hazardous nanoparticulate (NP) inks offe... more The fabrication of organic photovoltaics (OPVs) from non-hazardous nanoparticulate (NP) inks offers considerable promise for the development of ecofriendly large-scale printed solar modules. However, the typical NP core−shell morphology (driven by the different donor/acceptor affinities for the surfactant used in NP synthesis) currently hinders the photovoltaic performance. As such, surfactant engineering offers an elegant approach to synthesizing a more optimal intermixed NP morphology and hence an improved photovoltaic performance. In this work, the morphology of conventional sodium dodecyl sulfate (SDS) and 2-(3-thienyl) ethyloxybutylsulfonate (TEBS)-stabilized poly(3-hexylthiophene) (P3HT) donor:phenyl-C 61-butyric acid methyl ester (PC 61 BM) acceptor NPs is probed using scanning transmission X-ray microscopy, UV−vis spectroscopy, grazing-incidence X-ray diffraction, and scanning electron microscopy. While the SDS-stabilized NPs exhibit a size-independent core−shell morphology, this work reveals that TEBS-stabilized NPs deliver an intermixed morphology, the extent of which depends on the particle size. Consequently, by optimizing the TEBS-stabilized NP size and distribution, NP-OPV devices with a power conversion efficiency that is ∼50% higher on average than that of the corresponding SDS-based NP-OPV devices are produced.

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Design and analysis of grid connected biomass system utilizing chittagong municipal food waste

2017 3rd International Conference on Electrical Information and Communication Technology (EICT), 2017

An agricultural country like Bangladesh is facing insufficient electricity production system. All... more An agricultural country like Bangladesh is facing insufficient electricity production system. All of the expert bodies are trying to upgrade our electricity production system also trying to create various scopes for producing electricity. Therefore, we are offering a grid connected food wastage based biomass power plant because we have a lot of wastage and maximum of the wastage are vegetables and foods. We proposed renewable energy based power plant because it is environment friendly with less emission of carbon about 2% as well as others conventional power plant. For design and analysis, we have chosen Chittagong City Corporation because there are lot of food wastage in Chittagong. Also, the system is connected to national grid for upgrading our nation.

Current Research Paper Controlling the output of a variable speed wind turbine using pitch controller Environmental Science Environmental Science

Wind energy varies with year, season, and time of day, elevation above ground, and form of terrai... more Wind energy varies with year, season, and time of day, elevation above ground, and form of terrain. Because of fluctuating nature of the wind speed the variation of the output power occurs. When wind speed exceeds the rated speed of a turbine, the output power also exceeds the rated level. By controlling the pitch angle the output power of the wind turbine can be limited. The purpose of this work is to design a MATLAB\SIMULINK model of a wind turbine using pitch controller where at high wind speed region, the pitch controller will automatically active to maintain the output power at the rated level. From simulation result, it is observed that, at rated wind speed pitch angle is zero i.e. pitch controller remains inactive and above rated wind speed the pitch controller is activated and keep the output power at rated value by changing the value of pitch angle.

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A model for prediction of monthly solar radiation of different meterological locations of Bangladesh using aritficial neural network data mining tool

2017 International Conference on Electrical, Computer and Communication Engineering (ECCE), 2017

Solar energy generated by the sunlight is non schedulable due to the stochastic behavior of meteo... more Solar energy generated by the sunlight is non schedulable due to the stochastic behavior of meteorological conditions. Also the equipment for measuring the solar irradiance is expensive and rarely available in all locations of the globe. Hence prior knowledge of solar radiation is very important, for better management, sizing and control of solar energy installations. Predictive data mining such as Artificial Neural Network (ANN) is one of the most reliable and accurate model for forecasting solar radiation. There are a number of meteorological and geographical parameters which affect the solar radiation prediction model. So, identification of most influential parameters for better prediction accuracy is a crucial factor. In this paper, three attribute evaluators of Waikato Environment for Knowledge Analysis (WEKA) such as Classifier Subset Eval, CFS Subset Eval and Wrapper Subset Eval are used to select the most influential input parameters for ANN model for prediction of solar rad...

Plasmonic enhancement of aqueous processed organic photovoltaics

RSC Advances, 2021

Plasmonic NaxWO3 nanoparticles were introduced to aqueous processed organic photovoltaics with 35... more

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Effects of concentration profile on charge injection in continuously graded mixed-host organic light emitting diode

Thin Solid Films, 2016

Although the mixed-host organic light emitting diode (OLED) has been known for improved performan... more Although the mixed-host organic light emitting diode (OLED) has been known for improved performance, the charge injection and mobility may not be uniform in the light emitting layer (EML) hence affecting the exciton formation and recombination. In this work, we investigate the effects of concentration profiles of electron-and hole-transport materials in EML on the charge injection and confinement as a result of in-situ formation of transport layers by thermal evaporation of a pre-mixed source. Experimental results show that the OLED performance depends on the continuously graded concentration profiles, and are correlated to numerical simulations which reveal charge confinement, spatial shift of recombination zone and lowering of hole mobility.

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Building Intermixed Donor-Acceptor Architectures for Water-Processable Organic Photovoltaics

Physical Chemistry Chemical Physics, 2019

A modified synthesis method for aqueous nanoparticle printing inks, based upon vacuum-assisted so... more

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Electrical characteristics of two dimensionally modeled InGaN/InN/InGaN-based double channel HEMTs (DHEMTs)

2016 3rd International Conference on Electrical Engineering and Information Communication Technology (ICEEICT), 2016

In this paper, InGaN/InN/InGaN-based double channel HEMTs are investigated by numerical simulatio... more In this paper, InGaN/InN/InGaN-based double channel HEMTs are investigated by numerical simulation from the self-consistent solution of Schrodinger-Poisson systems. The influences of polarization charges and quantum effects are incorporated into this model. The simulation model predicts the two-dimensional electrical characteristics (internal electric fields and distribution of charges in the channel) that are associated with specified physical structures and bias conditions through the proper material parameters, the polarization field and surface states. Corresponding analysis and discussion based on the simulation results are subsequently given. This analysis provides a platform to investigate the InN-based double channel HEMTs and to optimize their design.

Effects of higher concentration of hole transport material on organic light emitting diode performance

2016 3rd International Conference on Electrical Engineering and Information Communication Technology (ICEEICT), 2016

The effects of higher hole transport material (HTM) composition on single emissive layer (EML) ba... more The effects of higher hole transport material (HTM) composition on single emissive layer (EML) based organic light emitting diode (OLED) performance are investigated quantitatively. Due to higher ratio of HTM in EML, the turn-on voltage is reduced from 3.5 V to 2.7 V. In parallel, OLED luminescence and current efficiency also increased with higher HTM concentration. This improvement of OLED performance because of higher HTM concentration in mixture of transport materials has been explained in terms of charge transport, carrier recombination and charge balancing in EML.

Numerical analysis of performance improvement of modified ITO based organic light emitting diode

2015 International Conference on Advances in Electrical Engineering (ICAEE), 2015

The effects of indium tin oxide (ITO) based anode work function modification on charge injection ... more The effects of indium tin oxide (ITO) based anode work function modification on charge injection at anode/organic layer interface and charge transport into the organic layers of organic light emitting diode (OLED) have been investigated quantitatively through this numerical simulation work. The improvement of device performances due to this anode surface modification also explained in this work in terms of simulated current density-voltage-luminance (J-V-L) characteristic, efficiency and recombination zone.

Effect of higher carrier injection rate on charge transport and recombination in mixed-host organic light emitting diode

2016 International Conference on Innovations in Science, Engineering and Technology (ICISET), 2016

The effect of anode surface modification on performance of uniformly mixed-host (MH) emissive lay... more The effect of anode surface modification on performance of uniformly mixed-host (MH) emissive layer (EML) based organic light emitting diode (OLED) has been investigated by the numerical simulation. Indium Tin Oxide (ITO) used as anode in the device. Due to proposed surface modification technique of ITO, the energy barrier at anode/organic layer interface is reduced which consummately enhanced the hole injection rate that leads to balance of carriers transportation and recombination in the EML. Through the numerical simulation, the electrical characteristics and internal device physics of uniform MH-OLED have been analyzed quantitatively. Calculated current balance factor which is related to the external quantum efficiency also confirmed the efficiency enhancement of MH-OLED by the proposed ITO work function modification technique.

Numerical study on ITO surface modification technique to improve single emissive layer based organic light emitting diode performance

2016 9th International Conference on Electrical and Computer Engineering (ICECE), 2016

To improve the performance and operational life time of an organic light emitting diode (OLED), a... more To improve the performance and operational life time of an organic light emitting diode (OLED), a single uniformly mixed-host (MH) emissive layer (EML) based OLED structure with modified anode surface has been proposed in this work. Through the numerical simulation, the feasibility of the proposed modified work function of ITO based device structure has been justified from the electrical characteristics and efficiency curves. By the ITO surface modification technique, the interfacial energy barrier of ITO/EML is reduced enough to increase hole injection rate into the EML. Therefore, the carriers become more balanced which raise the recombination rate in the EML. From the calculated current balance factor from the simulation results, it is confirmed that due to ITO surface modification, the proposed MH-OLED able to give better performance in terms of brightness, efficiency and longer operating time over unmodified ITO based MH-OLED.

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