Insertion of a TiOx layer between the Al electrode and the active layer of an organic photovoltaic cell resulted in a high performance with 94% durability under irradiation (100mW∕cm2) for 100h and had improved fill factor and open circuit voltage. An efficiency of 4.05% was achieved by using the cell containing a TiOx layer fabricated and measured in ambient atmosphere. The TiOx layer works as an effective barrier to physical damage and chemical degradation, resulting in high durability under aerobic conditions, and also serves as a hole blocking layer, resulting in improved parallel resistance and rectification.

Conjugated polymers with alternating main chain structures of zinc porphyrin−furan (PZnPF) and zinc porphyrin−thiophene (PZnPT) have been synthesized by palladium(0)-catalyzed Stille coupling reaction. The optical, electrochemical, photophysical, and photovoltaic properties of PZnPF and PZnPT were investigated to elucidate the effects of the heterole bridges (i.e., furan vs. thiophene) in the porphyrin polymers. The optical bandgap of PZnPF (1.75 eV) is smaller than that of PZnPT (1.90 eV), implying the high delocalization of the π-electrons along the polymer main chain of PZnPF relative to PZnPT. The more extended π-conjugation in PZnPF results from the smaller steric repulsion of the meso-furan moiety with the porphyrin rings than that of the meso-thiophene. The time-resolved fluorescence spectrum of PZnPF showed a gradual Stokes shift to the longer wavelength in the subnanosecond time domain due to the relaxation from a twisted conformation with the large dihedral angles between the porphyrins and the furan rings to a coplanar conformation with the small dihedral angles, whereas the fluorescence spectrum of PZnPT did not exhibit the dynamic Stokes shift. Both PZnPF and PZnPT are electrochemically active in the oxidation and reduction regions and have suitable HOMO/LUMO levels that enable photoinduced electron transfer from the polymer to [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in the blend films. Indeed, the blend films displayed strong fluorescence quenching from the porphyrin moieties together with appearance of charge-transfer emission arising from the interaction between the porphyrin and the C60 moieties. This is the first observation on charge-transfer emission between conjugated porphyrin polymers and fullerenes. Bulk heterojunction solar cells were fabricated by using the blend films of PZnPF:PCBM and PZnPT:PCBM as a photoactive layer. The PZnPF:PCBM and PZnPT:PCBM devices revealed power conversion efficiencies of 0.048% and 0.027% under standard AM1.5 sunlight (100 mW cm−2). These results obtained here will provide fundamental information on the design of large chromophore-embedded conjugated polymers for solar energy conversion.

Two mutants of the dibenzothiophene-desulfurizing Rhodococcus erythropolis KA2-5-1, strains MS51 and MS316, which express a high level of desulfurizing activity in the presence of sulfate, were isolated using the transposome technique. The level of dibenzothiophene-desulfurization by cell-free extracts prepared from mutants MS51 and MS316 grown on sulfate was about five-fold higher than that by cell-free extracts of the wild-type. This result was consistent with results of Western-blot analysis using antisera specific for DszA, DszB and DszC, the enzymes involved in the desulfurization of dibenzothiophene. Gene analysis of the mutants revealed that the same gene was disrupted in mutants MS51 and MS316 and that the transposon-inserted gene in these strains was the gene for cystathionine beta-synthase, cbs. The cbs mutants also expressed high levels of Dsz enzymes when methionine was used as the sole source of sulfur.