Materials Science Forum Vol. 846

Abstract: This work focused on the electrical and Hall Effect of Organic Solar cell (OSC). In this work, Indium Tin oxide (ITO) glass as substrate was heated at 50 °C to 200 °C. The polymer used was Poly (3-Dodecylthiophene) (P3DT) thin film and Downy Rose Myrtle berries (Rhodomyrtus Tomentosa (Ait.) Hassk.) as dye. The P3DT were deposited on the ITO substrate using electrochemistry method at room temperature. While, the dye of Downy Rose Myrtle berries was deposited by layered using spin coating method. The electrical conductivity of ITO deposited thin film was explored by four point probes (FPP) under dark and under light radiation (range of 10 Wm^-2 to 200Wm^-2). From FPP study, the electrical conductivity was increased by the increment of light intensity and temperature of substrate. Lastly, the samples were examined using Hall Effect measurement to obtain the type of sample, Hall mobility, and highest charge carrier in the sample of OSC. The results show that the sample is suitable for further solar cell application.

Abstract: The formation of nanocrystalline porous silicon (PS) was successfully prepared under a novel alternating current (sine-wave a.c. (50 Hz)) photo-assisted electrochemical (ACPEC) etching condition of an n-type (100) silicon (Si) substrate under the illumination of an incandescent white light. As grown Si and PS through conventional direct current(DC) anodization were also included for comparison. The ACPEC formed porous Silicon (PS) with excellent structural and surface morphological characteristic. According to the field emission scanning electron microscope (FESEM) micrographs, the nanoporous structures exhibited pores with uniform circular structure with estimated sizes, ranging between 20.5 nm and 30.5 nm. The atomic force microscopy (AFM) revealed an increase in the surface roughness induced by porosification. As compared to the as-grown Si, PS by AC method exhibited a substantial visible photoluminescence (PL) intensity enhancement with blue-shift associated with the quantum confinement effect of the nanostructure Si. Thermally treated nickel (Ni) finger contact was deposited on the PS to form MSM photodetector. Ni/PS MSM photodetector showed lower dark and higher photocurrent compared to the as grown Si device.

Abstract: This study highlights the structural, morphological, photovoltaic and electron transport properties of zinc oxide-multi-walled carbon nanotubes (ZnO-MWCNTs) based dye-sensitized solar cell (DSSC) prepared at different concentrations of 0.0, 0.1, 0.3 and 0.5 wt.%. The ZnO-MWCNTs thin films were prepared by a chemical bath deposition method. X-ray diffraction (XRD) analysis proved the formation of hexagonal wurtzite of the samples. The crystallite sizes, D of ZnO-MWCNTs was measured varies from 21 nm to 11 nm. The oat-like ZnO nanoflakes structure and the presence of MWCNTs were captured by field-emission scanning electron microscopy (FESEM) analysis. Transmission electron microscopy (TEM) analysis measured the inner (~6.81 nm) and outer (~28.31 nm) diameter of MWCNTs. The optimum concentration of 0.1 wt.% MWCNTs produced the highest photocurrent density, J_sc of 13.5 mA/cm², open-circuit voltage, V_oc of 0.149 V, fill factor, FF of 0.406 and power conversion efficiency, PCE of 0.817 %. Optimum doping of 0.1 wt.% MWCNTs generated short electron lifetime, τ_eff of 0.67 ms, low effective electron chemical diffusion coefficient, D_eff of 9.5 x 10^-8 cm² s^-1 and higher electron recombination rate, k_eff of 1497.48 s^-1. The addition of MWCNTs has influenced the structural, morphological, photovoltaic and electron transport properties of ZnO-MWCNTs based DSSC.

Abstract: This paper reports the effect of perovskite layer on enhancing the inverted type hybrid organic solar cell performance. The mixtures of methylammonium iodide (CH₃NH₃I) and lead (II) chloride (PbCl₂) were dissolved in N,N-Dimethylformamide (DMF) solvent and was spin-coated onto fluorine-doped tin oxide (FTO) glass substrate coated with zinc oxide nanorod arrays (ZnONRAs). The poly (3-hexylthiophene-2,5-diyl) (P3HT) film was then spin-coated onto CH₃NH₃I_(3-x)PbCl_x perovskite layer, followed by silver (Ag) deposition using magnetron sputtering technique. The FTO/ZnO seed/ZnONRAs/CH₃NH₃PbI_(3-x)Cl_x /P3HT/Ag device was fabricated. A device without perovskite layer was also fabricated for comparison. A power conversion efficiency (PCE) of 0.56% was achieved with the introduction of perovskite layer. The PCE was approximately six times greater than the device without perovskite layer, as a result of wider light absorption range and higher exciton dissociation efficiency.

Abstract: Titanium dioxide (TiO₂) based dye-sensitized solar cells (DSSCs) doped with reduced graphene oxide, rGO also known as graphene were fabricated at concentrations of 0.01 wt.% . The performance of TiO₂/graphene based DSSC and TiO₂ based DSSC were studied using electrolytes; PAN-based gel electrolyte. The thin films were characterized using several characterizations such as scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and current-voltage (I-V) measurement. The micrograph images obtained by SEM demonstrated that the thin films are highly porous. The XRD characterization showed that the crystalline particle of thin films is an anatase state and high percentage of carbon composition can be determined using EDX analysis. Through I-V characteristic, the current density J_sc, open circuit-voltage V_oc, fill-factor FF, and efficiency η of the TiO₂-based DSSC were 0.196 mA/cm2, 0.44 V, 0.496 and 0.043% respectively. I-V characteristic showed an increase in values for rGO/TiO₂ based DSSC such as J_sc = 1.177 mA/cm2, V_oc = 0.66 V, FF = 0.656 and η = 0.509%. The addition of rGO concentration has improved the efficiency of DSSC while the use of electrolyte gel can sustain the stability of the cell.

Abstract: Dielectric relaxation and conductivity of Ni_0.3Zn_0.7Fe₂O₄ (NZF) were studied in the frequency range between 0.01 Hz to 3 MHz and temperature range within 313 K to 473 K. The sample was prepared by mixing Zinc Oxide, Nickel Oxide and Iron Oxide and sintered at 1573 K for 10 hours long. Dielectric properties were studied using Novo Control Dielectric Spectrometer. Dielectric relaxation and conductivity phenomena were discussed using an empirical model to key out the dielectric relaxation process. Analyze peak frequency relaxation process consist of four slopes to explain the dielectric relaxation process. The conductivity of the sample indicates an activated process and activation energy of dc conductivity is 0.44 ± 0.01 eV.

Abstract: Silver-silica nanocomposites (Ag-SiO₂NCs) with various compositions were synthesized through sol-gel technique. The morphology, optical and thermal stability of the nanocomposite were investigated and was compared with pure sol-gel to determine the effects of the nanoparticles. Transmission electron microscopy (TEM) confirmed that SiO₂ was encapsulated Ag with mean size of 30 nm. Uv-vis spectroscopy shows that the surface plasmon resonance (SPR) peak show Ag-SiO₂ NCs were greatly reduce due to the SiO₂ particles. The permittivity and refractive index were decreased as the composition of Ag was increased at composition of 60% silver. The real permittivity is negative along the visible region. The trend stability of Ag-SiO₂NCs were increased with the increased amount of silver.

Abstract: Li⁺ and Zr²⁺ codoped NiO ceramics was successfully prepared from the mixture of commercial Li₂CO₃, ZrO₂ and NiO using solid state reaction. The mixture of varies Li⁺ concentration (x = 0.01, 0.02, 0.03, 0.05 and 0.1), Zr²⁺ (y = 0.02) and NiO were ball milled for 24 hours. The samples were calcined at 1000oC for 2 hours, pressed into pellet shape at 250 MPa and sintered at 1280°C for 10 hours. The sintered pellets were subjected to XRD, SEM, density testing and Impedance analyzer. XRD result shows the single phase formation of Li_xNi_1-x-0.02Zr_0.02O. The grain becomes larger with the increament of Li⁺ mole %. The dielectric constant of Li_xNi_1-x-0.02Zr_0.02 decrease with the increasing frequency. The NiO codoped with Li⁺ and Zr²⁺ can be use excellently at high frequencies.Keywords: NiO doped Li⁺ and Zr²⁺, dielectric constant, high frequency

Abstract: The Zn_(1-x)Ti_xAl₂O₄ (x = 0.00, 0.05, 0.15 & 0.25) nanocrystals thin films were prepared by sol-gel method. The properties of Zn_(1-x)Ti_xAl₂O₄ were investigated by X-ray diffraction (XRD), Atomic Force Microscope (AFM), Fourier transform infrared spectra (FTIR) and (UV-Vis). By indexing the XRD patterns, we identified three structural types which is ZnAl₂O₄, anatase and rutile. The addition of TiO₂ increased the crystallite size from 14.65 to 25.25 nm. The direct band gap was found to be around 3.35 to 3.84 eV. The addition of TiO₂ increased the crystallite size, surface roughness, and lattice parameters of the resultant films, evidently affecting their density and dielectric constant (). The thin films were characterized in the certain frequency to determine the using LCR spectrometer. The and density value of the Zn_(1-x)Ti_xAl₂O₄ films increase linearly from 8.56 to 13.48 and 4.60 to 4.70 g/cm³ with the increasing of x value, respectively. Based on the material analysis and microwave antenna theory, GPS patch antennas were fabricated using the Zn_(1-x)Ti_xAl₂O₄ material. The fabricated GPS antenna with the highest (13.48) material exhibits the smallest size of antenna which is 7.45 cm². The performances and the operating frequencies were measured using a PNA series network analyzer. The result showed that all patch antennas operate at frequency of 1.570 GHz. The GPS patch antenna fabricated from Zn_0.25Ti_0.75Al₂O₄ showed an excellent combination of return loss (-29.6 dB), smallest size (7.85 cm²), and wide bandwidth (195 MHz). All fabricated antennas are meets the requirements of GPS applications.

Abstract: Polycrystalline manganites compound of La_0.67A_0.33MnO₃ (A= Sr, Ca) has prepared by conventional solid state reaction method. In this work, an effort has been made to study the influences of substitution with different alkaline earth in La-site. The structural of La_0.67A_0.33MnO₃ was studied by X-ray diffraction patterns (XRD), XRD spectrums of La_0.67Ca_0.33MnO₃ (LCMO) showed in orthorhombic structure (space group Pbnm) while La_0.67Sr_0.33MnO₃ (LSMO) was in hexagonal structure (R-2c). The LCMO and LSMO bulks were investigated magnetically in view to understanding the ferromagnetic-paramagnetic (FM-PM) behaviors using vibrating sample magnetometer (VSM) at room temperature. LSMO bulk sample exhibited ferromagnetic with high in magnetization while LCMO bulk was in paramagnetic behaviors. The Curie temperature and metal-insulator transition temperature (T_p) were measured using AC Susceptibility (ACS) at temperature range 78 K- 300 K and four-point probe technique. The T_c for LCMO was 260 K, the curves coincide at temperatures above 240 K and become zero around the Curie critical temperature, where the FM-PM transition occurs and T_p for LCMO was reported around 250 K. Meanwhile, the T_c and T_p for LSMO were above 300 K. The difference in grain sizes of the microstructure images of LCMO and LSMO are might be due to the substitution of variance alkaline earth ions that differs in grain growth were observed using scanning electron microscopy (SEM). By replacing Sr²⁺ in La-Ca-MnO, the crystal structure transform from orthorhombic to hexagonal with highly symmetrical, thus the MnO₆ octahedral are less distortion and the local spins are relatively more aligned. Therefore, electron hopping interaction at sub-orbital (3d:e_g) increase, resulting the T_c and T_p are shifted to higher values