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An inverted-type organic bulk-heterojunction solar cell inserting zinc oxide (ZnO) as an electron collection electrode, fluorine-doped tin oxide (FTO)/ZnO/[6,6]-phenyl-C(61)-butyric acid methyl ester:regioregular poly(3-hexylthiophene) (PCBM:P3HT)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS)/Au, was fabricated in air and characterized by an alternating current impedance spectroscopy (IS). In the IS measurement, we observed reproducibly the electric resistance and capacitance components originating from ZnO and organic active layers, and we found that the depletion layer functioning to take out the photocurrent to the external circuit was formed in both the ZnO and PCBM:P3HT layers at the ZnO/PCBM:P3HT interface. In this letter, we propose that this IS measurement is effective for evaluating the electric properties of several layers with capacitance components in organic thin-film solar cells.

An indium tin oxide/titanium oxide/[6,6]-phenyl C 61 butyric acid methyl ester: regioregular poly(3-hexylthiophene)/poly(3,4-ethylenedioxylenethiophene): poly(4-styrene sulfonic acid)/Au type organic solar cell (ITO/TiO x /PCBM:P3HT/PEDOT:PSS/Au) with 1 cm 2 active area, which is called "inverted type solar cell", was developed using an ITO/amorphous titanium oxide (TiO x ) electrode prepared by a sol-gel technique instead of the low functional electrode such as Al. The power conversion efficiency (η) of 2.47 % was obtained by irradiating AM 1.5G-100 mW cm -2 simulated sunlight. We found that a photoconduction of TiO x by irradiating UV light containing slightly into the simulated sunlight was required to drive this solar cell. The device durability in an ambient atmosphere was maintained for more than 20 h under continuous light irradiation. Further, when the air-stable device was covered by a glass plate with water getter sheet which was coated by an epoxy UV resin as sealing material, the durability was still higher and over 96 % of relative efficiency was observed even after continuous light irradiation for 120 h.

Ultrafast photoinduced spin dynamics has been investigated by time-resolved magneto-optical Kerr spectroscopy for various ferromagnetic and ferrimagnetic compounds: FeCr2S4, CoCr2S4, CuCr2Se4, CdCr2Se4, La0.6Sr0.4MnO3, and SrRuO3. The temporal demagnetization process, which is observed commonly for all the compounds, essentially consists of two components: One is an instantaneous change which originates perhaps from multiple emissions of magnetic excitations during nonradiative decay of photoexcited carriers, and the other is a delayed response due to thermalization of the spin system. The time constant of the delayed change depends strongly on materials and is scaled with the magnetocrystalline anisotropy, indicating that spin-orbit coupling is a dominant interaction for this process.

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