Solid State Phenomena Vol. 301

Abstract: Solid state dye-sensitized solar cell (ss-DSSC) was developed to overcome the problem arise from electrolyte leakage in liquid state dye-sensitized solar cell. This work focused on the fabrication of ss-DSSC based on inorganic semiconductor of titania and organic conducting polymer of poly (3-hexylthiophene) (P3HT) and natural dyes from purple seaweed (PS dyes) via electrochemical, spin coating and dip coating method, respectively. The absorption spectrum and functional group of PS dyes were investigated using UV-Visible absorption spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy; respectively. Meanwhile, the effect of immersion time of PS dyes on performance of the device was studied via current density-voltage (J-V) characteristic. PS dye was absorbed in a wide range of solar spectrum in visible and near-IR region by chlorophyll a, phycocyanin and zeaxanthin pigments exists in the PS dyes. The present of carboxylic groups in PS dyes which bound to P3HT and formed P3HT-COOH enable the linkage to TiO₂ surface which helps in the transfer of electrons from natural dyes to the conduction band of TiO₂ film. The highest efficiency obtained was 1.44% at 10 minutes time of immersion. This concludes that PS dyes was a good photosensitizer and can be applied in ss-DSSC.

Abstract: This paper reports broadband anti-reflection in black silicon (b-Si) fabricated by two-step metal-assisted chemical etching (MACE) for potential photovoltaic (PV) applications. The method involves deposition of silver nanoparticles (Ag NPs) in aqueous solution of HF:AgNO₃, followed by etching in HF:H₂O₂:DI H₂O solution for different duration (10-25 s). Effects of etching time towards surface morphological and optical properties of b-Si nanowires are investigated. Surface morphological characterization confirms presence of b-Si nanowires with heights of 350-570 nm and diameter of 150-300 nm. The b-Si nanowires exhibit outstanding broadband anti-reflection due to refractive index grading effect. This is represented as weighted average reflection (WAR) in the 300-1100 nm wavelength region. After 20 s of etching, b-Si nanowires with height of 570 nm and width of about 200 nm are produced. The nanowires demonstrate WAR of 5.5%, which represents the lowest WAR in this investigation. This results in absorption of 95.6% at wavelength of 600 nm. The enhanced broadband light absorption yields maximum potential short-circuit current density (J_sc(max)) of up to 39.7 mA/cm², or 51% enhancement compared to c-Si reference. This facile b-Si fabrication method for broadband enhanced anti-reflection could be a promising technique to produce potential PV devices with high photocurrent.

Abstract: Photocatalytic fuel cell (PFC) is promising to own its synchronous degradation of organic pollutants with electricity generation under illumination of light. The oxidation and reduction process promote the conversion of chemical energy in the pollutants into electrical energy. In this study, PFC is driven by the electrode reactions between the zinc oxide loaded carbon plate (ZnO/C) photoanode and carbon plate cathode under irradiation of UVA light. The ZnO/C photoanode was successfully fabricated by using simple ultrasonication-annealed method and investigated by XRD, SEM and EDX. To investigate the capability of the PFC, reactive red 120 (RR120), congo red (CR) and acid orange 7 (AO7) are employed well compared among themselves. The results indicated that the molecular structure of azo dyes with different adsorption of light by dye itself, number of azo bonds and sulfonic groups can be the crucial factors of decolorization in the PFC. The photocatalytic fuel cell with AO7 as sacrificial agent was able to perform 82.43% of decolorization efficiency, a maximum short circuit current (J_SC) of 0.0017 mA cm^-2 and maximum power density (P_max) of 0.0886 µW cm^-2.

Abstract: Thin crystalline silicon (c-Si) suffers from poor light absorption which hinders generation of high photocurrent in photovoltaic (PV) devices. To overcome this issue, efficient light trapping (LT) schemes need to be incorporated into the thin c-Si absorber. This paper presents ray tracing of LT schemes in thin c-Si to enhance broadband light absorption within 300-1200 nm wavelength region. For the ray tracing, mono c-Si wafer with 100 μm thickness is investigated and solar spectrum (AM1.5G) at normal incidence is used. Front and rear pyramid textures, silicon nitride (SiN_x) anti-reflective coating (ARC) and back surface reflector (BSR) are the LT schemes being studied in this work. With incremental LT schemes, optical properties of the thin c-Si are analyzed. From the absorption curve, maximum potential photocurrent density (J_max) is calculated, assuming unity carrier collection. The c-Si reference (without LT) exhibits J_max of 24.93 mA/cm². With incorporation of incremental LT schemes into the thin c-Si, the J_max increases, owing to enhanced light coupling and light scattering in the c-Si absorber. The J_max up to 42.12 mA/cm² is achieved when all the LT schemes are incorporated into the thin c-Si absorber. This represents 69% enhancement when compared to the J_max of the c-Si reference.

Abstract: LiCo_0.9X_0.1O₂ (where X=Mn and Fe) were synthesized using self-propagating combustion (SPC) method using citric acid as a combustion agent. The precursors of LiCo_0.9X_0.1O₂ were annealed at a temperature of 800 °C at 24 h. The phase and crystalinity of the materials were characterized using X-Ray Diffraction (XRD). All the materials were observed to be single and pure phase with no impurity peaks detected. The morphology and particle sizes of the materials were also analyzed using Field Emission Scanning Electron Microcopy (FESEM). Finally, the electrochemical performance of the materials was studied using charge-discharge cycling in the voltage range of 2.5 to 4.3 V. Based on the results from charge-discharge studies, Mn substituted cathode materials exhibit better specific discharge capacity compared with Fe substituted cathode materials.

Abstract: The sample with nominal composition of Bi_1.6Pb_0.4Sr₂Ca_2-xEu_xCu₃O_y where x = 0.000, 0.0025, 0.020, 0.050 and 0.100 were synthesized through solid state reaction method. The effect of Eu₂O₃ nanoparticles doping on the superconducting and structural properties were studied by means of critical temperature, T_C, critical current density, J_C, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The amount of 2223 phase gradually decreased with the increment of Eu concentration which indicates that Eu nanoparticles substitution at Ca site favours the growth of 2212 phases. The sample with higher porosity was found to be decreased in critical temperature, T_C as well as critical current density, J_C due to the lack of effective surface area for current flowing. The best superconducting properties were observed at x = 0.0025 substitutes into Ca site for Bi (Pb)-2223 host sample.

Abstract: Mesoporous silica material was first discovered by Mobil research group in 1990s. Its nanoscale form is favorable due to their properties such as high specific surface area, tunable sizes and easy surface functionalization. Mesoporous silica nanoparticles (MSNs) is commonly synthesize through condensation of silica source in the presence of templates. Two most commonly used templates are cetyltrimethylammonium bromide (CTAB) and polymer PF-127. However, in these recent years, new templates were discovered and one of it is ionic liquids (ILs). ILs are salt that has melting point below 100 °C and its core structure is similar to CTAB which consist of large organic cations and inorganic or organic anions. Therefore, it has the potential to serve as alternative template in formation of MSNs. This work reported usage of two long chain imidazolium ILs as template in the synthesis of monodispersed mesoporous silica nanospheres (MNSs). The effect of imidazolium ILs alkyl chain length on properties of MNSs were investigated. It was found that particle size of MNSs decreases with alkyl chain length of imidazolium ILs. The porosity of the MNSs were further analyzed through nitrogen sorption analysis where the surface areas were 570.61 and 598.71 m² g^-1 and pore volume up to 1.4 cm³ g^-1.

Abstract: Natural based film have been studied as a possible replacement for the conventional films because it can be developed from natural sources. The aim of this study is to investigate the effect of acetylation contact time to the physical and mechanical properties of the jackfruit rind based cellulose acetate film. Acetylation of jackfruit rind based cellulose was studied and samples with different degree of substitution were obtained as a function of contact time from 1 hour to 24 hours. The products were characterized by saponification reaction. In this study, saponifcation reaction showed that, more hydroxyl group were substituted with acetyl groups as the contact time of acetylation increased. The Cellulose Acetate (CA) had been mixed in the gelatine matrix film. The addition of jackfruit rind based CA showed that the moisture uptake and solubility of the film decreased compared to Cellulose/Gelatine composite film. This is because acetyl groups are more hydrophobic than hydroxyl groups thus reducing the hydophilic nature of cellulose. Additionally, from the tensile test, it was proven that the film with CA of 24 hours contact time exhibits the highest tensile strength.

Abstract: Composite laminate design is an important procedure in defining the mechanical properties of laminated composite structure to be used in multi-directional service loading application. Composite technologies or manufacturers who is lack of knowledge regarding the importance of laminate design, tend to develop a composite structure that will collapse or fail below the service requirement. The purpose of this study is to determine the effect of fiber orientation on flexural properties of the designed glass fiber reinforced epoxy laminated composite. Six sets of laminates with different fiber orientation and sequence were simulated using CompositeStar© software to determine its flexural properties. Samples were fabricated to verify the simulated data and were tested in accordance to ASTM D2344. Moreover, crack pattern within the samples after the flexural test is studied. From the simulated results, it shows that laminates which have fiber in tri-direction and quasi-direction display a higher flexural modulus and strength compared to laminates with fiber in uni-directional and bi-directional. In addition, data from tested fabricated laminates samples displayed the same modulus patterns against the simulated data, with variants from 8% to 35%. Additionally, it is found that samples with fiber in ±45 direction shows a transverse and shear cracking which prolonged the cracking propagation before the samples show a complete failure.