Pepen Arifin

A new architecture for solar cells involving a metal bridge deposited between active TiO2 particles

The efficiency of titanium dioxide (TiO2)-based film solar cells fabricated by combined spray and electroplating methods was improved by forming metal bridges in the pores between TiO2 nanoparticles. The interfaces between TiO2 nanoparticles and metal bridges formed Schottky contacts, which minimized recombination of electron-hole pairs and increased electron transfer. A maximum efficiency of 4.38% was achieved for cells plated at 50 mA and 55 °C. This efficiency is higher than that reported for solar cells with a similar structure [Saehana et al., AIP Conf. Proc. 1284, 154 (2010); 1415, 163 (2011); IJBAS/IJENS 11, 15 (2011)]. We also identified that both current and temperature influence the morphology of the metal bridges and efficiency of the solar cell.

Dye-Sensitized Solar Cells (DSSC) from Black Rice and its Performance Improvement by Depositing Interconnected Copper (Copper Bridge) into the Space between TiO2 Nanoparticles

Dye-sensitized solar cell (DSSC) which employed natural dye from black rice has been successfully fabricated and improved its performance by depositing interconnected copper (copper bridge) on the space between TiO2. The copper bridge has significant role in minimizing recombination of electron-hole which occurred in TiO2 surface by trapping electron and facilitating to anode. The presence of interconnected copper nanoparticle in the space between TiO2 nanoparticle was confirmed by Scanning Electron Microscopy (SEM) and X-Ray Diffractometer (XRD). The current-voltage (I-V) characterization of DSSC solar cells by using Keithley 617 was also performed to investigate performance of solar cells under sun illumination in varying intensities. It is found that performance of copper coated DSSC solar cells (efficiency 0.35% and fill factor 0.35) is higher than DSSC without copper coating (efficiency 0.17% and fill factor 0.35). This result is consistent with impedance spectroscopy analyzing where the internal resistance of copper coated DSSC solar cells is lower than DSSC without coated. It is concluded that performance of DSSC increasing with decreasing of internal resistance. Our finding is higher than other researcher reports in Ref. [13] and [14] with similar structure and kind of natural dye. In addition, this paper also reports the use of polymer electrolyte which employing polyvinyl acetate (PVA) containing lithium ion to maintain long-term stability of device.

Performance Improvement of TiO 2 Based Solar Cells by Coating Cu Nanoparticles into the Space between TiO 2

TiO 2 thin films with its pore coated by copper (Cu) nanoparticles have been developed in order to improve the TiO 2 based solar cells performance. Contact between Cu nanoparticles and TiO 2 play role in minimizing the recombination of electron‐hole pairs and increasing electron transfer in TiO 2 based solar cells. The Cu coating on the space between TiO 2 has been performed by electroplating methods. It is found that the solar cells performance of Cu coated TiO 2 films become higher than of the pure TiO 2 film. The presence of Cu nanoparticles on TiO 2 films were confirmed from Scanning Electron Microscopy (SEM). In this study, a maximum conversion efficiency of 3.73% was achieved.

Au/n-GaN Schottky diode grown on Si(111) by plasma assisted MOCVD

Most of the growth of GaN epilayers by MOCVD method reported to date was carried out at growth temperature above 1000/spl deg/C on sapphire substrates. We have successfully grown GaN by plasma assisted MOCVD (PA-MOCVD) method at temperature between 560/spl deg/C to 650/spl deg/C. In this paper we report an attempt to fabricate Au/n-GaN Schottky diode grown on Si(111) by PA-MOCVD method. The GaN films were grown at temperatures of 625/spl deg/C and 650/spl deg/C using trimethylgallium (TMGa) and nitrogen plasma. The diode is a concentric type using aluminum as ohmic contact and gold as Schottky contact. Electrical characterizations were performed by I-V and C-V measurements. The barrier heights determined from I-V measurements are 0.44 eV and 0.49 eV, for Schottky diodes grown at 625/spl deg/C and 650/spl deg/C, respectively. The ideality factors are 4.5 and 5.6 indicate that tunneling as the main mechanism of electron transport through the barrier. This mechanism is typical for moderately to highly doped semiconductor, as confirmed from C-V measurement.

Effect of Growth Temperature on Cobalt-Doped TiO2 Thin Films Deposited on Si (100) Substrate by MOCVD Technique

Co:TiO2 (cobalt-doped titanium dioxide) thin films have been deposited on the n-type Si (100) substrate at the temperatures range of 325°C 450°C using MOCVD (metal organic chemical vapor deposition) technique. We investigated the effect of growth temperature on the structural and morphological quality of Co:TiO2 thin films. The structure of Co:TiO2 thin films were characterized by XRD while the morphology and the thickness of films were characterized by SEM. The XRD results reveal that all films show the anatase structure and the dominant orientation of anatase phase depends on the growth temperature. The grain size of crystal increases as the growth temperature increases. We also reveal that the growth rate of Co:TiO2 film has a maximum value at the growth temperature of 400°C.

Surface morphology, electrical and optical properties n-type doped MOCVD grown GaSb using dimethyltellurium

Abstract Dimethyltelluride has been used as a dopant source for GaSb epilayers grown via atmospheric pressure metalorganic chemical vapour deposition (MOCVD). It has been observed that the electron concentration (n) is proportional to the Te partial pressure in the vapour phase, until n saturates at high Te partial pressure. Electron concentrations as high as 1.36 × 1018 cm– 3 have been measured with imperfect morphology, and as high as 1.22 × 1018 cm– 3 with excellent, mirror like, morphology. These appear to be the highest electron concentrations reported to date for any MOCVD-growth epitaxial n-type GaSb doped with DMTe and grown at 540 °C with a V/III ratio of 1.4. The absorption spectra of GaSb doped with DMTe show that the heavily doped samples have a less abrupt edge. The absorption coefficient (α) strongly depends on the free carrier concentration. PL spectra of the epilayers are also reported.

The influence of hydrogen plasma and annealing on GaN film grown by plasma-assisted MOCVD

We have studied the influence of hydrogen plasma treatment and annealing on GaN mms grown by plasma-assisted metal organic chemical vapor deposition (MOCVD). The X-ray diffraction (XRD) pattern of GaN films grown without assistance of hydrogen plasma show misoriented polycrystalline structure, while those grown with the assistance of hydrogen plasma show a crystalline structure with (0001) orientation. Post-growth hydrogenation and annealing reduces the carrier concentration of fUms grown without hydrogen plasma, but does not give a significant effect for mms grown with the assistance of a hydrogen plasma.

GaSb quantum dots and its microanalysis using X-ray photoelectron spectroscopy (XPS)

Nanostructures have become a topic of increasing interest due to their fundamental properties and possible device applications. One method of fabrication that is receiving much attention lately is the utilization of the coherent Stranski-Krastanov mode which leads to self-assembly of small-scale islands, driven by the lattice mismatch between the quantum dot material and the underlying substrate material [1–5]. W e quantitatively investigate initial stages of growth and evolution of GaSb islands on GaAs substrates grown by metalorganic chemical vapor deposition (MOCVD). We pay particular attention to the transition from 2D to 3D growth and to the transition between isolated island growth and the coalescence of islands in an effort to improve our understanding of this regime. The extent of oxidation and growth derived oxygen contamination for GaSb quantum dots grown by metalorganic chemical vapour deposition (MOCVD) were also investigated by X-ray photoelectron spectroscopy (XPS) using a system with high energy resolution.

Growth of Al x Ga 1−x N epitaxial thin film on sapphire substrate by plasma assisted metal organic chemical vapor deposition (PA-MOCVD)

This paper reported the study of growth of AlxGa1−xN thin film on a-plane sapphire substrate using plasma assisted metal organic chemical vapor deposition (PA-MOCVD). We have successfully growth the Al content AlGaN alloys and investigated the influence of TMA/TMAl+TMGa flow rate ratio to their crystal structure and surface morphology. From S EM image and XRD measurement, the AlGaN films grown with TMA/TMAl+TMGa flow rate ratio of 20% have single crystal orientation, homogeneous and smoother surface morphology. From ED X microanalysis results, all of the AlGaN alloys have high Al content. The Al content of the AlGaN alloys with TMA/TMAl+TMGa flow rate ratio of 20%, 30%, and 40% is about x = 0.5, 0.6, and 0.65, respectively and grown at the growth temperature about of 700°C.

Plasma-assisted MOCVD growth of GaMnN

The growth of GaMnN thin films on c-plane sapphire substrate by plasma-assisted metalorganic chemical vapor deposition (PAMOCVD) method is reported. Cyclopentadienyl manganese tricarbonyl (Cp2MnT) was used as a source of Mn. The growth was conducted at varied growth temperature in the range of 625 to 700°C and V/III flux ratios between 440 and 1080. The growth rate and Mn incorporation into GaN highly depend on growth parameters. From the analysis of XRD spectra, it was found that the highest Mn incorporation into GaMnN which would produce single phase GaMnN (0002) was 6.4 % at growth temperature of 650°C. While at growth temperature of 700°C, the maximum of Mn incorporation into GaMnN films that would still produce single phase film were 3.2 %. The surface roughness of the films determined from AFM image results showing that high growth temperatures tend to improve the surface morphology of GaMnN. The results of magnetization measurement shows hysteresis behavior at room temperature with various values of coercivity, saturation and remnant magnetization in the range of 350-800 Oe, 20-39 emu/cm3 and 10.2–34.4 emu/cm3, respectively depend on the Mn concentration. For the films grown at 650 °C, the highest magnetic moment per Mn-atom was obtained by a sample with Mn concentration of 2.0 %, i.e. 3.1 µΒ/Mn-atom. While for the films grown at 700°C, the highest magnetic moment per Mn-atom was obtained by a sample with Mn concentration of 2.5 %, i.e. 3.7 µΒ /Mn-atom.