Safizan Shaari
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Preferred name
Safizan Shaari
Official Name
Safizan, Shaari
Alternative Name
Shaari, Safizan
Shaari, S.
Main Affiliation
Scopus Author ID
55807708700
Researcher ID
AAR-5562-2021

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Solvent Effect on the Electrical and Structural Properties for MEH-PPV Organic Light Emitting Diodes (OLED)

2021-03-01 , Ismail N.A.N. , Safizan Shaari , Juhari N. , Norhayati Sabani , Ahmad M.F. , Zakaria N.F.

In this paper, the performance of the electrical properties (J-V) and surface roughness of MEH-PPV based organic light-emitting diodes (OLED) towards solvent effect was investigated. The MEH-PPV layer was deposited using spin coating technique at fixed spun speed of 3000 rpm. Two different solvents, toluene and chloroform (CHCl3) and mixture toluene:CHCl3 with the ratio of 4:1 and 1:4 were used to dilute MEH-PPV at fixed concentration of 5 mgml-1. Apparently, the mixture of solvent makes the surface roughness of the MEH-PPV films reduced to 0.15 nm and 3.59 nm under the ratio 4:1 and 1:4 respectively. Besides, the mixture solvents makes the value of turn on voltage was dropped to ∼7.2 V and ∼9 V respectively compared to non-mixture solvent. The combination of different solvent apparently gives an effect on the electrical and structural properties of organic light-emitting diode.

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Optimization of MEH-PPV based single and double-layer TOLED structure by numerical simulation

2021-12 , T. Kersenan , Nor Farhani Zakaria , Safizan Shaari , Norhayati Sabani , Nurjuliana Juhari , Meor Ahmad Faris bin Meor Ahmad Tajudin , A.F.A Rahim

In this work, we simulated and characterized Poly [2-methoxy-5-(2’-ethylhexyloxy)-1, 4-phenylene vinylene] (MEH-PPV) based single and double-layer TOLED by using Silvaco ATLAS device simulator to achieve prominent values of electrical and optical properties of the device. MEH-PPV were used as the emitting layer (EML) in the single-layer, while addition of Poly [(3,4-ethylene dioxythiophene)-poly(styrene sulfonate)] (PEDOT-PSS) as the electron transport layer (ETL) were conducted in double-layer TOLED simulation. The EML and ETL thickness in both structures were varied between 10 – 150 nm, respectively, to observe and understand the underlying physics of the relation in the layer thickness to the electrical and optical characteristics. Furthermore, variation of the EML/ETL thickness ratio from 1:1 to 5:1 (with thickness in between 10 to 50 nm) had also been conducted. From this work, it is understood that the thickness of the EML layer plays the most important role in TOLED, and by balancing the carrier injections and recombination rate in appropriate EML/ETL thickness ratio, the electrical and optical properties can be improved. By optimizing the EML/ETL thickness and thickness ratio, an optimal forward current of 1.41 mA and luminescent power of 1.93e-18 W/μm has been achieved with both MEH-PPV and PEDOT-PSS layer thickness of 10 nm (1:1 ratio), respectively. The results from this work will assist the improvement of TOLED device to be implemented widely in low power and transparent electronic appliances.

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The efficiency effect of dye sensitized solar cell using different ratio of organic polymer doped titanium dioxide at different annealing process temperature

2020-01-08 , Norhisamudin N.A. , Norhayati Sabani , Rosli N. , Mohd Fairus Ahmad , Juhari N. , Safizan Shaari , Zakaria N.

Titanium Dioxide (TiO2) is one of the main materials in Dye Sensitized Solar Cell (DSSC). It is well known with its property of good optical transmittance and its mesoporous surface that can absorb generous amount of dye. In this study, TiO2 is fabricated using spin coating technique that leads to the uniform thickness of TiO2 layer. The thickness of the TiO2 can be controlled layer by layer using same technique to get an optimized surface that can lead to better performance of DSSC. In order to achieve this, the surface roughness of TiO2 must be as high as possible. Therefore, the organic material which is Poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene-vinylene (MEH-PPV) is used as medium to increase the mesoporous roughness structure of TiO2 nanocrystal film for DSSC. MEH-PPV is doped into the TiO2 using 0.5 mg/ml with different temperatures of 100°C and 450°C. Different temperatures of MEH-PPV will lead to the different surface structures for TiO2 thin film. The ratio of TiO2:MEH-PPV used were 1:1 and 2:1. The surface of TiO2 thin film was characterized using Atomic Force Microscope (AFM). The efficiency was obtained using Solar Simulator based on the voltage and current flow. Based on the results, the increment of surface roughness is about 21% for the different ratio at various temperatures. The optimum temperature and suitable ratio of TiO2:MEH-PPV was obtained via annealing process at 450°C with the ratio of 2:1. It gives the highest efficiency which is 0.1266%. These two important findings yield good mesoporous surface of TiO2 thin film.

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A review of visible-to-UV photon upconversion systems based on triplet–triplet annihilation photon upconversion

2022-12 , Kelvin Voon Yan Jie , Mohd Fairus Ahmad , Muhammad Mahyiddin Ramli , Safizan Shaari , Arif Mawardi Ismail , Yusran Sulaiman

Due to the tunable spectrum range and potential application under non-coherent solar irradiation, triplet-triplet annihilation based molecular photon upconversion (TTA-UC) systems represent a compelling study field for a variety of photonic implementations. There were studies on the incorporation of TTA-UC technology with photovoltaic technology, which made it possible to further improve the energy harvest performance through the utilisation of the wasted spectrum. However, many TTA-UC studies are limited to energy upconversion within the visible spectrum range. For photovoltaic cells with a higher band gap, which harvest the higher energy spectrum (UV region), an efficient Vis-to-UV upconversion is preferred. The Vis-to-UV TTA-UC system was first introduced in 2006. Recently, more studies were conducted to discover the Vis-to-UV upconversion system with high quantum efficiency and low excitation intensity such as the nanocrystal sensitizerbased system and the thermally activated delayed fluorescence sensitizer-based system. Recent studies in the solvent system of Vis-to-UV upconversion system had demonstrated the dependence of the couple photostability on the solvent and extended the solvent selection to inorganic solvent. In this review, we are reviewing the research background of the Vis-to-UV TTA-UC system and discussing the current challenges and potential developments in this research area.

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Modification of photoanode surface structure via image analysis on organic polymer material based for dye-sensitized solar cell (DSSC) applications

2021-12 , N. Rosli , Norhayati Sabani , MF Ahmad , Mohd. Azarulsani Md. Azidin , Nurjuliana Juhari , NF Zakaria , Mohd Natashah Norizan , Safizan Shaari

In this study, the experiment on the modification of the photoanode with organic polymer material as copolymer template for dye-sensitized solar cell (DSSC) applications has been conducted. The two organic copolymer templates are polystyrene sphere (PS) and poly[2- methoxy-5(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). The modification photoanodes were made using Dr. Blade’s method. These organic copolymer templates were added to improve the surface of the mesoporous titanium dioxide (TiO₂) layer, which is used as the main component in DSSC photoanode. The unmodified TiO₂ photoanode has poor aggregation and porosity of TiO₂. The addition of either MEH-PPV or PS sphere to the photoanode layer was found to affect the surface of mesoporous TiO₂ in terms of porosity, particle size distribution and shape. The analysis of the TiO2 modification was conducted using an image analysis processing method via a 2D scanning electron microscope (SEM) image. The image analysis processing method used was the ImageJ program. The DSSC of modified photoanode is fabricated using metal complex dye, Ruthenium (N719) dye. The data collected from the ImageJ program showed that by adding organic copolymer templates into TiO₂, the porosity of TiO₂ decreased from 45 % to 42 %. From the photovoltaic analysis obtained, the J-V characteristic is recorded with the photoanode of TiO₂ mixed with 1.00 wt% MEH-PPV gave the highest efficiency, which is 0.01 % with the following parameters – Voc = 0.43 V, Jsc = 0.17 mA/cm2 and FF = 0.20. Meanwhile, the photoanode of TiO₂ mixed with 0.50 wt% PS sphere gave the highest efficiency which is 0.08 % with the following parameters – Voc = 0.39 V, Jsc = 0.86 mA/cm2 and FF = 0.25.

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Hybrid Statistical and Numerical Analysis in Structural Optimization of Silicon-Based RF Detector in 5G Network

2022-02-01 , Yi Liang T. , Nor Farhani Zakaria , Shahrir Rizal Kasjoo , Safizan Shaari , Muammar Mohamad Isa , Mohd Khairuddin Md Arshad , Singh A.K. , Sobri S.A.

In this study, a hybrid statistical analysis (Taguchi method supported by analysis of variance (ANOVA) and regression analysis) and numerical analysis (utilizing a Silvaco device simulator) was implemented to optimize the structural parameters of silicon-on-insulator (SOI)-based self-switching diodes (SSDs) to achieve a high responsivity value as a radio frequency (RF) detector. Statistical calculation was applied to study the relationship between the control factors and the output performance of an RF detector in terms of the peak curvature coefficient value and its corresponding bias voltage. Subsequently, a series of numerical simulations were performed based on Taguchi’s experimental design. The optimization results indicated an optimized curvature coefficient and voltage peak of 26.4260 V−1 and 0.05 V, respectively. The alternating current transient analysis from 3 to 10 GHz showed the highest mean current at 5 GHz and a cut-off frequency of approximately 6.50 GHz, indicating a prominent ability to function as an RF detector at 5G related frequencies.

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Visible Light-Assisted Charge Extraction in High-Band-Gap SrTiO3 through the Integration of a Triplet Sensitizer-Emitter Thin Film

2024-01-22 , Jie K.V.Y. , Mohd Fairus Ahmad , Mohmad A.R. , Ismail A.M. , Mohd Natashah Norizan , Ramli M.M. , Safizan Shaari , Sulaiman Y. , Shamsul Amir Abdul Rais , Shazlina Johari

A challenge in PV designs, including those with an electron transport layer (ETL), is the presence of ‘parasitic absorbers’. These are layers that absorb light without significantly converting it to electrical current, impacting the total external quantum efficiency (EQE). Strontium titanate (STO), a high-band-gap (3.20 eV) perovskite metal oxide, holds promise as an electron transport layer (ETL) for solar energy harvesting. Despite STO’s potential, it primarily operates in the UV spectrum, not fully utilizing the broader light range, and hence can be the source of parasitic absorbers. In this study, we report a significant enhancement in the EQE of STO through the integration of a triplet sensitizer-emitter (TSE) system, designed to upconvert the visible spectrum into UV light and improve the charge extraction from STO. The TSE system uses carbazolyl dicyanobenzene (4CzIPN) as a sensitizer and p-terphenyl (TP) as an emitter. To investigate the EQE of such a system, we fabricate STO as a PV cell. The revised PV cell architecture (ITO/TiO2/STO/TSE/PEDOT:PSS/Al) is a modification of the conventional configurations (ITO/TiO2/STO/PEDOT:PSS/Al). With the TSE thin film, the modified STO PV cell shows better charge extraction under sunlight compared to the standard STO PV cell, indicating that the upconversion process can enhance the hole conductions from STO to PEDOT:PSS through the TSE system. We noted an EQE increase with intense light of λ > 345 nm in thicker TSE layers and a decrease in the EQE under similar light intensity in thinner TSE layers. The Kelvin probe force measurement (KPFM) data showed that the TSE layer receives holes from STO under illumination. Additionally, time-resolved photoluminescence (TRPL) experiments showed that the TSE/STO thin film is able to produce UV emission after irradiation with lower energy light. Then, the EQE variation in thicker TSE layers under intense irradiation can be attributed to the solid-state upconversion, indicating its thickness-dependent performance. These findings underline the strategies for maximizing the utilization of the solar spectrum in PV applications.

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Silicon Self-Switching Diode (SSD) as a Full-Wave Bridge Rectifier in 5G Networks Frequencies

2022-12-01 , Yi Liang T. , Nor Farhani Zakaria , Shahrir Rizal Kasjoo , Safizan Shaari , Muammar Mohamad Isa , Mohd Khairuddin Md Arshad , Singh A.K.

The rapid growth of wireless technology has improved the network’s technology from 4G to 5G, with sub-6 GHz being the centre of attention as the primary communication spectrum band. To effectively benefit this exclusive network, the improvement in the mm-wave detection of this range is crucial. In this work, a silicon self-switching device (SSD) based full-wave bridge rectifier was proposed as a candidate for a usable RF-DC converter in this frequency range. SSD has a similar operation to a conventional pn junction diode, but with advantages in fabrication simplicity where it does not require doping and junctions. The optimized structure of the SSD was cascaded and arranged to create a functional full-wave bridge rectifier with a quadratic relationship between the input voltage and outputs current. AC transient analysis and theoretical calculation performed on the full-wave rectifier shows an estimated cut-off frequency at ~12 GHz, with calculated responsivity and noise equivalent power of 1956.72 V/W and 2.3753 pW/Hz1/2, respectively. These results show the capability of silicon SSD to function as a full-wave bridge rectifier and is a potential candidate for RF-DC conversion in the targeted 5G frequency band and can be exploited for future energy harvesting application.

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Numerical simulation and characterization of silicon based OR logic gate operation using self-switching device

2021-12 , Y.X. Goh , Nor Farhani Zakaria , Y. L. Tan , Shahrir Rizal Kasjoo , Safizan Shaari , Muammar Mohamad Isa , A. K. Singh

Logic gates are the main components inside the integrated circuit used for almost every technological application. Nowadays, in order to enhance the performance of the smart device, while targeting in cut down of the fabrication cost and achieve low power consumption, lithography-based VLSI design technology on silicon are still being widely applied. Hence, an OR gate structure, a silicon based self-switching device (SSD) is introduced and investigated in this project. Such device is believed capable to act as an alternative for a low-powered logic gate application, suitable for CMOS devices. The SSD has an advantage in term of simplicity in fabrication process with a very low threshold voltage. Since SSD characteristics is similar to a conventional diode characteristic, the gate is designed in ATLAS Silvaco device simulator based on a diode logic to perform OR logic function after a validation of the physical and materials parameters. The electrical characterization and structural analysis were also done to observe the electrical performance and physical condition in the device. The simulated design showed a good OR logic output response with the inputs, and acceptable output ranged from around 4.5 to 4.8 V with 5 V HIGH inputs. The results from this OR gate characterization may assist in developing the logic gate for device integration and may act as a reference for future complex integrated circuit design.

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The modelling of SiC Gate Oxide thickness based on thermal oxidation temperatures and durations for high-voltage applications

2023 , Nuralia Syahida Hashim , Banu Poobalan , Nor Farhani Zakaria , Manikandan Natarajan , Safizan Shaari

This research has shown that the oxide thickness for silicon carbide (SiC) based wide materials can be predicted using regression techniques in wet/dry nitrided or wet/dry non-nitrided thermal oxidation process conditions for high voltage applications by employing 2 different regression techniques: Polynomial and linear regression. The R-squared (R2) and Mean Absolute Percentage Error (MAPE) techniques are used to evaluate the regression models. Furthermore, this work investigates and presents a calculation of gate oxide thickness that is correlated to gate voltage ranges for high voltage applications. In this work, the thermal oxidation process environment is classified into 3 different processing conditions: conventional (dry and wet), dry nitrided (NO,N2O), and wet nitrided (HNO3 vapour). The findings from this study showed that wet oxidation combined with nitrided elements can produce thicker and better-quality gate oxide as compared to conventional dry and wet oxidation techniques. The outcome of this work clearly shows that gate oxide thickness may be derived from silicon carbide-based wide-bandgap materials utilizing linear and polynomial approaches using thermal oxidation durations at different temperatures for high-power applications. The regression models and formulations produced in this work are expected to aid the researchers in determining appropriate oxide thickness under practicable process conditions, with the exception of real thermal oxidation process conditions. Hence, the outcome of this work is expected to save the processing time, material, and cost of the power semiconductor device fabrication technology, mainly for high voltage applications.

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