We employed a low-cost solution-processed ultrathin insulating polymeric layer of poly(4-hydroxystyrene) (PHS), with a high glass transition temperature (T g $ 185 C), as an interfacial layer between the polymer:fullerene photoactive layer and the Al negative electrode for enhancing device power conversion efficiency (PCE) of polymer bulk-heterojunction photovoltaic cells and investigated the roles of the interfacial nanolayer by ultraviolet photoemission spectroscopy and capacitance-voltage measurement. The thin polymeric layer forms a dipole layer and causes the vacuum level of the adjacent negative electrode to shift upward, which resulted in an increase of the built-in potential. As a result, the open-circuit voltage and PCE of the device using a PHS nanolayer were remarkably improved. We finally achieved a very high PCE of 6.5% with the PHS/Al negative electrode which is even much better than that of the device using an Al electrode (5.0%). The solutionprocessed inexpensive PHS layer with a high T g can be an attractive alternative to conventional vacuum-deposited low-work-function metal and insulating metal fluoride interfacial layers.

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Thin-film transistors (TFTs) utilizing a TiZnSnO (TZTO) channel layer were fabricated by using a solution process. The effect of annealing temperature on the device performance of the TZTO TFTs was investigated. TFTs with nanocrystalline TZTO films exhibited a better device performance than those with amorphous TZTO films. The on/off current ratio of the TZTO TFTs annealed at 600°C was as large as 4.2 Â 10 6 . The field-effect mobility (l FE ) of 4.1 cm 2 /Vs and subthreshold swing of 1.2 V/decade were achieved.

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