Hendri Widiyandari

Fabrication and Characterization of a Yellow-Emitting BCNO Phosphor for White Light-Emitting Diodes

A yellow-emitting phosphor comprised of boron, carbon, nitrogen, and oxygen (BCNO) atoms without any rare-earth ions as luminescence centers was successfully synthesized using a facile process at low temperature and atmospheric pressure. The synthesized BCNO powders showed a broad emission spectrum centered at 540 nm under excitation at 460 nm due to the radiation transitions of local 2 H g → 1 Σ - g luminescence provided in the BO - 2 species. Further analysis revealed that the BCNO yellow phosphor exhibited a high external quantum efficiency (60%) having a hexagonal-BN crystalline structure mixed with cubic-B 2 O 3 . The synthesized yellow-emitting BCNO phosphor is promising for high-efficiency phosphor conversion-based white light-emitting diodes.

Dye-sensitized solar cell based carbon nanotube as counter electrode

The counter electrode using Carbon nanotube (CNT) has been successfully fabricated by the doctor blade method and their performances were investigated. We found that increasing mass of the CNT powder in binder increases electrocatalytic activity which this beneficial to conversion efficiency of the Dye-sensitized solar cell (DSSC). The photovoltaic performance of the DSSCs with 0.01, 0.02 and 0.04 gr of the CNT obtained overall conversion efficiencies of 0.32%, 0.74% and 0.91%, respectively. The results suggest that the CNT counter electrode has potential as alternative to the Pt free counter electrode for DSSC.

TE and TM modes polaritons in multilayer system comprise of a PML-type magnetoelectric multiferroics and ferroelectrics

In this paper, we report our study on both bulk and surface polaritons generated in Multilayer system. The multilayer consists of ferroelectric and multiferroic with canted spins structure. The effective medium approximation is employed to derive the dispersion relation for both bulk and surface modes. Surface and bulk polaritons are calculated numerically for the case of Transverse electric (TE) and Transverse magnetic (TM) modes. Example results are presented using parameters appropriate for BaMnF4/BaAl2O4. We found in both TE and TM modes, that the region where the surface modes may exist is affected by the volume fraction of the multiferroics. The region of the surface modes decrease when the volume fraction of the multiferroic is reduced. This region decrement suppress the surface polariton curves which result in shortening the surface modes curves.

Synthesis of Tungsten Oxide (WO3) Film on Glass Substrate Using Aqueous Based Solution Spray Deposition Method

A Tungsten oxide (WO3) film on top of a glass substrate had been successfully constructed. The immobilization of tungsten oxide was performed using spray-deposition method. The precursor volume was varied as 5 mL, 10 mL and 25 mL. Characterization using XRD and SEM yield that precursor volume influence the quality of the film. It was found that the good uniform film was obtained using precursor volume 5 mL and 10 mL. The crack which was resulted from non-uniformity of the film appear when the precursor film was 25 mL.

Fluorine doped-tin oxide prepared using spray method for dye sensitized solar cell application

Fluorine-doped Tin Oxide (FTO) film was fabricated by spray deposition method. FTO films were prepared in different sheet resistance 6.7, 12.1, 19.3, and 23.5 Ω/sq. X-ray diffractograms showed that the as-grown FTO film was tetragonal SnO2. The prepared FTO film have an average transmittance of 80% in the visible region (λ=400-800 nm). These FTO films were then used to fabricate Dye Sensitized Solar Cell (DSSC). The working electrode was made from TiO2 paste using doctor blade technique. DSSC samples were characterized using solar simulator under AM 1.5 (100 mW/cm2). It is found that the efficiency of DSSC was much affected by sheet resistance of FTO film. The efficiency of DCCS was 2.32, 2.4, 1.1 and 0.97 (%) for the FTO sheet resistance 6.7, 12.1, 19.3, and 23.5 Ω/sq, respectively. It is shown that the optimum DSSC efficiency was made from FTO with sheet resistance 12.1 Ω/sq.Fluorine-doped Tin Oxide (FTO) film was fabricated by spray deposition method. FTO films were prepared in different sheet resistance 6.7, 12.1, 19.3, and 23.5 Ω/sq. X-ray diffractograms showed that the as-grown FTO film was tetragonal SnO2. The prepared FTO film have an average transmittance of 80% in the visible region (λ=400-800 nm). These FTO films were then used to fabricate Dye Sensitized Solar Cell (DSSC). The working electrode was made from TiO2 paste using doctor blade technique. DSSC samples were characterized using solar simulator under AM 1.5 (100 mW/cm2). It is found that the efficiency of DSSC was much affected by sheet resistance of FTO film. The efficiency of DCCS was 2.32, 2.4, 1.1 and 0.97 (%) for the FTO sheet resistance 6.7, 12.1, 19.3, and 23.5 Ω/sq, respectively. It is shown that the optimum DSSC efficiency was made from FTO with sheet resistance 12.1 Ω/sq.

Synthesis and characterization carboxyl functionalized Multi-Walled Carbon Nanotubes (MWCNT-COOH) and NH2 functionalized Multi-Walled Carbon Nanotubes (MWCNTNH2)

A making of MWCNTs-COOH has been conducted to improve the compatibility of carbon nanotubes and MWCNTs-NH2, in order to have conductive properties. The MWCNTs- COOH study was performed, using the first reflux method using HNO3 for 6 hours heated with 60°C (concentrated HNO3 ratio with MWCNTs is 1: 5), followed by the second reflux using SOCl2 for 5 hours heated to 70°C (concentrated HNO3 ratio with MWCNTs is 1: 3). Meanwhile, the making of MWCNTs-NH2 used homogenization process, used magnetic stirrer, with comparison between MWCNTs-COOH with Etanadiamine 1: 2000, for 8 hours at 40oC. Both products were analyzed using Fourier transform infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). The C-O bond on MWCNTs-COOH is indicated by absorption at wavelength 1672.28 cm-1 and O-H bond at 3431.36 cm-1 N-H bond on MWCNTs-NH2 shown at wavelength 1440.83. The SEM analysis indicates that both products have a tubular surface morphology.

Polyvinilidine fluoride (PVDF) nanofiber membrane for Li-ion rechargeable battery separator

This study reported synthesis and characterization of PVDF (polyvinilidine fluoride) nanofiber membrane using electrospinning method for Li-ion rechargeable battery separator. Electrospinning equipment system consists of a DC high voltage (HV - DC), a controllable spinner and a plate collector. The effects of the applied voltage on morphological property, porosity and thermal property were systematically investigated. The application of DC voltage at a range of 13 to 17 kV resulted the one-dimension nanostructure of the PVdF nanofiber. The produced PVdF nanofiber membrane separators are evaluated to have a higher level of porosity (86 – 93%) and a good thermal shrinkage property in comparison to Polypropylene (PP) microporous membrane separator. The produced PVdF membrane separators were assembled into the LiFePO4 cells and demonstrated high charge-discharge capacities at room temperature with the coulombic efficiency reaching 80 %.

Dye-sensitized solar cell based on TiO2/MnO2 composite film as working electrode

The purpose of this study is to develop DSSC based on TiO2/MnO2 composite film as working electrode. The working electrodes were prepared by the doctor blade method and their characteristics were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis spectroscopy. Moreover, the performance of DSSCs was performed under simulated AM 1.5G solar illumination using 100 mW/cm2. The indirect band gap of TiO2 pure, TiO2/MnO2 and TiO2/MnO2 6% films are 3.29, 2.98 and 2.81 eV, respectively. The highest power conversion was 0.018 % which corresponds to TiO2/MnO2 6% composite film. The results suggest that the MnO2 added to the semiconductor TiO2 can improve the efficiency of the DSSCs.

Polaritons in magnetoelectric multiferroics films: Switching magnon polaritons using an electric field

ABSTRACT We present a theoretical study of polarions on the magnetoelectric multiferroics with finite thickness (film) geometry. The multiferroics are ferroelectric-antiferromagnet with canted spin structure. Dispersion relation for surface and bulk polaritons are calculated for the case of transverse electric (TE) polarization. Example results are presented using parameters appropriate for BaMnF4. It is found that bulk polaritons posses discreet character due to the film geometry. We also found that there are two branches of surface polaritons which are reciprocal. Example results for attenuated total reflection (ATR) are also presented. Analyzing the ATR reflection, we found that the branches of surface polaritons are able to be switched by applying an electric field opposite to the polarization.

Characterization of Nephelium Lappaceum Peel Extract as a Dye Sensitized Solar Cell

The world now is searching for a new renewable alternative energy. Nephelium lappaceum is a popular fruit in Indonesia that contains anthocyanin. Anthocyanin can absorb light on the range of visible light due to its conjugated double bonds. This finding makes Nephelium lappaceum as a potential Dye Sensitized Solar Cell (DSSC). The Nephelium lappaceum extract can be taken through extraction technique, called maserasi. The process of developing DSSC material was initiated by preparing TiO2 photoanode using a conventional sintering procedure. It was, then, followed by doping TiO2 on the Fluoride doped tin oxcide (FTO) with resistance value of 10-20 ohm/q. Finally, the electrode counter made of platinum paste was developed by implementing conventional sintering procedure. All of the above process were then continued by the DSSC assembly. In this process, the TiO2 photoanode which has passed the absorption process for 24 hours, was doped on the counter electrode. After doping, the process was stopped by doing electrolyte solution filling into prepared electrode counter holes. In order to characterize the DSSC, a solar simulator connected to a computer was employed. Based on this characterization process, it was found that the maximum value of Voc was 0.29 V, the maximum value of current density was 0.56 mA / cm2, the maximum power was 0.062 mW / cm2 and efficiency of 0.063. Characteristics of Nephelium lappaceum peel extract is one of the DSSC cells using TiO2 as a semiconductor material as a dye sensitizer that can convert light energy into electrical energy.