The photovoltaic performance of organic− inorganic hybrid films based on regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) and ZnO nanorods depends strongly on the quality of the interfaces between the organic polymer and the inorganic nanostructures. A thin, solutionprocessed TiO 2 interlayer was introduced on the surface of ZnO nanorods to improve the interface between ZnO and P3HT. In order to understand the effects of the TiO 2 interlayer on the initial photophysical processes after photoexcitation, femtosecond time-resolved fluorescence dynamics of the hybrid ZnO nanorods/P3HT (ZnO/P3HT) films with or without TiO 2 interlayer coating were comparatively studied using a fluorescence up-conversion technique. Because of the wellaligned P3HT nanodomains in these annealed hybrid films, energetically downhill excitation energy transfer was found to be the dominant process in the subps time scale with an excitation at 400 nm. The fluorescence decay times for the ZnO−TiO 2 /P3HT film were significantly extended, which is likely due to the improved interface quality with fewer traps and defects when TiO 2 interlayer was introduced. Moreover, ultrafast anisotropy decay and a dramatic decrease in residual anisotropy at the emission of 660 nm were observed for the ZnO−TiO 2 /P3HT film in comparison to both P3HT pristine film and the ZnO/P3HT film. This suggests a change in the disorder of energy, the local field, and an efficient energy-transfer process, resulting in a faster exciton reaction (dissociation) within the ZnO−TiO 2 /P3HT film. Solar cells fabricated using TiO 2 -coated ZnO nanorods and P3HT showed efficiencies of up to 0.76%, a 58% improvement over the TiO 2 -free equivalent devices.

Solution-processed organic-inorganic hybrid bulk heterojunction solar cells with the capability of broadband solar photon harvesting over the ultraviolet-visible-near-infrared spectral range are developed. A series of mixed (porphyrinato)(phthalocyaninato) rare-earth double-decker complexes, [M III H(TClPP){Pc(a-OC 4 H 9 ) 8 }] (1-7; M ¼ Y, Sm, Eu, Tb, Dy, Ho, Lu; TClPP ¼ meso-tetrakis(4chlorophenyl)porphyrinate; Pc(a-OC 4 H 9 ) 8 ¼ 1,4,8,11,15,18,22,25-octakis(1-butyloxy) phthalocyaninate) and [Y III (TClPP)(Pc)] (8, Pc ¼ unsubstituted phthalocyaninate), along with a heteroleptic bis(phthalocyaninato) yttrium double-decker complex [Y III H(Pc){Pc(a-OC 4 H 9 ) 8 }] (9), are synthesized and utilized as broadband absorbers and electron donors (D), whereas N,N 0 -bis(1ethylhexyl)-3,4:9,10-perylenebis(dicarbox-imide) (PDI) or [6,6]-phenyl-C 61 butyric acid methyl ester (PCBM) is adopted as primary electron acceptor (A 1 ). For suppressing the fatal back charge transfer at D/A 1 interface, the D:A 1 blend is fabricated within an in situ formed cheap inorganic network of nanoporous TiO x , which can act as a secondary electron acceptor (A 2 ). For characterization of these structures, steady state spectroscopy, fluorescence dynamics, atomic force microscopy, current-voltage characteristics, and photoelectrical properties of the active materials or devices are investigated. Solar cells utilizing PDI as the primary acceptor show higher values in open circuit voltage, fill factor, and power conversion efficiency over those cells using PCBM as the primary acceptor. With a cell area of 0.36 cm 2 , good efficiencies of up to 0.82% are achieved by the aforementioned double-decker complex: PDI:TiO x blends under 1-sun air mass 1.5 global illumination. These results conclude that doubledecker bis(tetrapyrrole) complexes are promising photovoltaic materials with tunable absorption and photophysical properties.

Abstract. Cu 2 ZnSnS 4 (CZTS) was obtained from a sol-gel precursor which consists of copper chloride, zinc chloride, tin chloride, and thiourea. CZTS thin films were prepared by spincoating the sol-gel precursor followed by annealing in a nitrogen atmosphere. The morphology, composition, and structure of the absorber layer were studied by scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, and Raman scattering. The optical measurement shows the bandgap of these films is ∼1.51 eV, and the optical absorption coefficient is on the order of 10 4 cm −1 . CZTS solar cells with a structure of low-alkali glass/Mo/CZTS/CdS/iZnO/ZnO:Al/Al grid were tentatively fabricated. The best solar cell showed a short-circuit current density of 5.06 mA/cm2 , an open-circuit voltage of 358 mV, a fill factor of 34.66%, and an efficiency of 0.63% under AM1.5 (100 mW/cm 2 ) illumination. These results demonstrate the CZTS thin films were successfully deposited by a cheap sol-gel technique. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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