Tungsten oxide ͑WO 3 ͒ was inserted as an anode interfacial layer between the photoactive layer and top electrode in inverted polymer solar cells ͑PSCs͒ with nanocrystalline titanium dioxide as an electron selective layer. The device with WO 3 exhibited a remarkable improvement in power conversion efficiency compared with that without WO 3 , which indicated that WO 3 efficiently prevented the recombination of charge carriers at the organic/top electrode interface. The dependence of the device performances on WO 3 film thickness and different top metal electrodes was investigated. Transparent inverted PSCs with thermally evaporable Ag/ WO 3 as a transparent anode were also investigated when introducing a WO 3 buffer layer.
Molybdenum trioxide ͑MoO 3 ͒ was inserted between the active layer and top electrode in inverted polymer solar cells ͑PSCs͒ with nanocrystalline titanium dioxide as an electron selective layer. The performances of structurally identical PSCs with different top electrodes ͑Au, Ag, and Al͒ were investigated and compared. The interface between MoO 3 and different metals was studied by x-ray photoelectron spectroscopy. The results showed that the performances of devices with different metals are greatly improved due to the incorporation of MoO 3 and the open-circuit voltage of devices is relatively insensitive to the choice of the anode metal when MoO 3 is introduced.
BioCARS, a NIH-supported national user facility for macromolecular time-resolved X-ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded undulator-based beamline optimized for single-shot laser-pump X-ray-probe measurements with time resolution as short as 100 ps. The source consists of two in-line undulators with periods of 23 and 27 mm that together provide high-flux pink-beam capability at 12 keV as well as first-harmonic coverage from 6.8 to 19 keV. A high-heat-load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick-Baez mirror system capable of focusing the X-ray beam to a spot size of 90 µm horizontal by 20 µm vertical. A high-speed chopper isolates single X-ray pulses at 1 kHz in both hybrid and 24-bunch modes of the APS storage ring. In hybrid mode each isolated X-ray pulse delivers up to ~4 × 10(10) photons to the sample, thereby achieving a time-averaged flux approaching that of fourth-generation X-FEL sources. A new high-power picosecond laser system delivers pulses tunable over the wavelength range 450-2000 nm. These pulses are synchronized to the storage-ring RF clock with long-term stability better than 10 ps RMS. Monochromatic experimental capability with Biosafety Level 3 certification has been retained.
Nanocrystalline TiO2 thin films were prepared by sol-gel method and were then used to fabricate metal-semiconductor-metal ultraviolet photodetectors with Au Schottky contact. It was found that dark current of the fabricated devices was only 1.9nA at 5V applied bias. High responsivity of 199A∕W was achieved when it was irradiated by the ultraviolet light (λ=260nm). The low dark current and high responsivity maybe attributed to the effect of Schottky barrier in company with neutral semiconductor owing to the wide finger gap of 20μm. The devices show a slow time response with a rise time of 6s and a decay time of 15s. The authors deduced that the slow time response was caused by defect traps which were widely distributed in nanocrysal.
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