Results 1 - 10 of 52
Results 1 - 10 of 52. Search took: 0.015 seconds
|Sort by: date | relevance|
[en] During investigations of Au - a-Si:H - Cr-Sb photovoltaic Schottky diodes, it was observed that photoconversion parameters (Isc,, Voc, η), improved markedly with time for samples stored for several weeks in ambient air. This was always accompanied by apparent color changes in the area under the top (Au) electrode, from gold to deep purple, and by evolution of its surface conductivity σ from a highly conducting to an insulating state. Profilometry indicated that the colored area rose about 80 nm above the original surface during these changes. These diodes have been examined using depth-profiling surface analytical techniques, namely secondary-ion mass spectroscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy (XPS), but primarily the latter. The XPS studies of the entire layer thickness on the gold electrode were carried out using erosion by Ar+ ion bombardment. The XPS line positions were used to infer electrical properties of silicon and gold constituents. The results show that Si atoms first diffuse through the gold electrode, where they react with atmospheric constituents to form a thick layer composed mainly of SiO2. this layer is responsible for the observed changes in color, σ, and Isc. The latter change, which leads to a maximum rise in η of about 60%, is felt to result from the fact that the SiO2 layer acts as an antireflection coating. Gold from the electrode layer also diffuses outward, mixed intimately with the silicon oxide. Further aging results in a degradation of the electrical continuity of the Au electrode, which is believed to be responsible for the observed slow drop in σ. (author). 14 refs., 9 figs
[en] In this paper, a graphene/InP thin-film Schottky-junction solar cell with a periodic array of plasmonic back-reflector is proposed. In this structure, a single-layer graphene sheet is deposited on the surface of the InP to form a Schottky junction. Then, the layer stack of the proposed solar-cell is optimized to have a maximum optical absorption of 〈A W〉 = 0.985 (98.5%) and short-circuit current density of J sc = 33.01 mA cm−2. (paper)
[en] We report a theoretical study about the performances of graphene on semiconductor Schottky barrier solar cells with the aim to show the potentiality of this kind of device. The simulations are carried by a generalized equivalent circuit model, where the circuital parameters are strictly dependent on the physical properties of the graphene and semiconductor which form the Schottky junction. We have realized graphene samples and characterized them by optical and atomic force microscopy, and Raman spectroscopy. Capacitance–voltage measurements have been made on some “ad hoc” graphene based devices in order to obtain graphene workfunction, a very essential physical parameter. The estimated value is compatible with four layer graphene. This result is in agreement with the morphological characterizations of our material. - Highlights: ► An equivalent circuit model simulates graphene based Schottky barrier solar cells. ► Graphene flakes are identified through Raman spectroscopy and Atomic Force Microscopy. ► Workfunction estimation by Capacitance–Voltage (C–V) on graphene based devices ► A multilayered structure is evidenced by morphological and C–V characterization.
[en] We report on first-principles calculations of the properties of the MoSe2/Mo(110) interface. Due to mismatch between the lattice parameters of the two structures, different patterns can form at the interface. We have studied the formation energy and the band alignment of six patterns for the MoSe2 (0001)/Mo(110) interface and one pattern for the MoSe2 (1120)/Mo(110) interface. The MoSe2 (1120)/Mo(110) interface is more stable than the MoSe2 (0001)/Mo(110) interface and in contrast to MoSe2 (0001)/Mo(110), no Schottky barrier forms at MoSe2 (1120)/Mo(110). Doping with Na modifies the band alignment at the interfaces. The Schottky barrier height decreases, provided that a Na atom occupies a Mo atom site in MoSe2 films. (authors)
[en] A Schottky diode with configuration Au/Carmine/p-Si/Al has been fabricated and it has been seen that the thin film on the p-Si substrate has exhibited a good rectifying behavior. The current-voltage (I-V) characteristics of the device have been investigated in dark before electron irradiation and under white light illumination and after 12 MeV electron irradiation with fluency of 3x1012 e-/cm2. It has been seen that the device is sensitive to illumination and to electron irradiation. The barrier height value has decreased under illumination. The ideality factor and series resistance values have increased by 12 MeV electron irradiation. Furthermore, it has also seen that the reverse bias current and capacitance of the device have decreased after electron irradiation. This has been attributed to decrease in net ionized dopant concentration with electron irradiation.
[en] Highlights: • Graphene/silicon solar cells have been fabricated. • Graphene p-doping was obtained through the cell exposure to vapor of HNO3 or SOCl2. • A double antireflection coating was deposited on the top of the cell. • Chemical interactions with acids explain cells electrical behavior. • The optimal doping-antireflection combination for graphene solar cells is proposed. - Abstract: In the present work we have tested the effects of two of the most used graphene chemical dopants, nitric acid (HNO3) and thionyl chloride (SOCl2), on multilayer graphene/n-silicon (G/n-Si) Schottky barrier solar cell completed with a double antireflection coating (DARC). The DARC has been realized with a MgF2/ZnS thermal deposition on graphene. In both cases the graphene doping process performed before DARC deposition increases the graphene conductivity and the work function, leading to cells with larger open circuit voltage and higher efficiency. After DARC layer realization a second acid exposure is necessary to compensate a partial de-doping effect and restore graphene doping. However the electrical characterization shows that the DARC/G/n-Si finite solar cell behaves differently with the two dopants. It is noteworthy that the presence of DARC does not prevent a further re-doping with HNO3, allowing the fabrication of cells with 8,5% efficiency which is not the case with SOCl2: this effect was explained by different chemical interactions between graphene, the deposited DARC and the two doping substances.
[en] To overcome the naturally existing Schottky barrier problem between p-CdTe and any metal, an intermediate semiconductor thin buffer layer is a better choice prior to the final metallization for contact. Among many investigated back contact materials the ZnTe is suitable as a buffer layer. ZnTe thin films were deposited onto glass substrates by the thermal evaporation technique under vacuum approx. equal to 2 X 10/sup -5/mbar. Undoped ZnTe thin films are highly resistive, extrinsic doping of Cu was made to improve the electrical conductivity. Films were doped by immersing in Cu NO/sub 3/)sub 2)/.5H/sub 2/O solutions for Cu doping. To optimize the growth parameters the prepared films were characterized using various techniques. The structural analysis of these films was performed by X-ray diffraction (XRD) technique and optical transmission. X-ray diffraction identified the phases present in these films and also observed that the prepared films were polycrystalline. Also the spectral dependence of absorption coefficient was determined from spectrophotometer. Energy band gap index were calculated from obtained optical measurements data. (author)
[en] CuIn5Se8 homogeneous crystals of n-type conductivity have been grown. Donor centers activation energy has been estimated. In/n-CuIn5Se8 Schottky barriers have been created and the first spectral dependencies of quantum efficiency of photoconversion of these structures have been derived. The nature of interband optical transitions has been interpreted and the band gap values for direct and indirect transitions in CuIn5Se8 crystals have been determined on the results of analysis of the Schottky barriers photoactive edge absorption. A possibility of utilization of CuIn5Se8 crystals in wide-band photoconverters of the optical radiation has been established
[en] Full text : In this work the spectral dependence of the photoconductivity, ESR and IR absorption spectra of a-Si0.80Ge0.20 : H films and also based on a-Si0.80Ge0.20 : H solar cell structures of the p-i-n junction and Pt/a-Si0.80Ge0.20 : H Schottky-barrier types are examined. The results of the carried out studies make it possible to maintain that a-Si0.80Ge0.20 : H material involved is thermodynamically stable and it is of important for manufacturing solar energy converters. Solar cells with the energy conversion efficiency of 5.9 and 4.2 percent for p-i-n and Pt/a-Si0.80Ge0.20 : H structures, respectively, have been obtained