No abstract

In this study, we investigated the high fill factor (FF) and high power conversion efficiency (PCE) of organic photovoltaic (OPV) cells using a dual hole-transporting layer (HTL) of vanadium oxide (V2O5)/copper phthalocyanine (CuPc) as a buffer layer. The OPV cell configuration consists of indium tin oxide (ITO)/V2O5/CuPc/poly(3-hexylthiophene) (P3HT):phenyl C61-butyric acid methylester (PCBM)/LiF/Al. The FF and PCE of the device with a V2O5/CuPc buffer layer are approximately threefold and tenfold, respectively, greater than those of a conventional device without the buffer layer. The FF and PCE of the device are 62.2 and 2.11%, respectively, under a simulated AM1.5G illumination of 100 mW/cm2. The increased PCE and FF of the device are obtained using a V2O5/CuPc buffer layer, which is attributed to the stepwise hole-transporting configuration and the increased optical absorption from the anode.

We report on tunneling spectroscopy measurements using a scanning tunneling microscope (STM) on the spin triplet superconductor Sr 2 RuO 4 . A fully open gap, close to the Bardeen-Cooper-Schrieffer (BCS) value, is found, which disappears at the bulk T c = 1.5 K. The results are discussed in the framework of recent multigap scenarios for an unconventional spin triplet superconductor. Superconductivity in the ruthenate compound Sr 2 RuO 4 has puzzled many scientists in the past decade [1]. A number of experiments, reviewed in [2], show that this superconductor could become the metallic analogue to superfluid 3 He. Strong indications that this material may be indeed an odd parity superconductor [3] have been repeatedly found since the first report for the absence of a change in the Knight shift in NMR experiments [4]. Sr 2 RuO 4 crystallizes in the layered perovskite structure common to cuprates [1]; it has a critical temperature T c of 1.5 K, and is a good metallic system with a relatively simple Fermi surface consisting of three nearly cylindrical sheets, all of them derived from the Ru 4d orbitals, and mass renormalization factors between 3 and 5.5 [5]. Identifying the structure of the superconducting gap over the Fermi surface is of prime importance for understanding spin triplet superconductivity in this material. In high quality samples, the electronic contribution to the specific heat at the lowest temperatures extrapolates very close to zero [6]. The curves do not show activated behavior, which has been taken as evidence for the presence of nodes somewhere on the Fermi surface [2]. Other

No abstract

Bi4Ti3O12 thin films are deposited on indium tin oxide (ITO)/glass substrates using RF magnetron sputtering technology and are annealed at 675 °C in a rapid thermal annealing furnace in an oxygen atmosphere. The resulting films have high optical transmittances and good crystalline characteristics. ZnS:TbOF films are then deposited on the Bi4Ti3O12 films, causing the originally highly transparent specimens to blacken and to resemble a glass surface coated with carbon powder. The optical transmittance of the specimen is less than 15% under the visible wavelength range, and neither a crystalline phase nor a distinct ZnS grain structure is evident in X-ray diffractometer (XRD) and scanning electronic microscope (SEM). Secondary ion mass spectrometer (SIMS) analysis reveals the occurrence of interdiffusion between the ZnS and Bi4Ti3O12 layers. This suggests that one or more unknown chemical reactions take place among the elements Bi, S, and O at the interface during the deposition of ZnS:TbOF film on a Bi4Ti3O12/ITO/glass substrate. These reactions cause the visible transmittance of the specimens to deteriorate dramatically. To prevent interdiffusion, a silicon dioxide (SiO2) buffer layer 100 nm thick was grown on the Bi4Ti3O12/ITO/glass substrate using plasma-enhanced chemical vapor deposition (PECVD), then the ZnS:TbOF film was grown on the SiO2 buffer layer. The transmittance of the resulting specimen is enhanced approximately 8-fold in the visible region. XRD patterns reveal the ZnS(111)-oriented phase is dominant. Furthermore, dense, crack-free ZnS:TbOF grains are observed by SEM. The results imply that the SiO2 buffer layer sandwiched between the ZnS:TbOF and Bi4Ti3O2 layers effectively separates the two layers. Therefore, interdiffusion and chemical reactions are prevented at the interface of the two layers, and the crystalline characteristics of the ZnS:TbOF layer and the optical transmittance of the specimen are improved as a result. Finally, the dielectric constant of the stacked structure is lower than that of the single layer structure without SiO2, but the dielectric breakdown strength is enhanced.