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We report on curved film microstructure arrays fabricated through polydimethylsiloxane (PDMS) film buckling induced by mechanical stretching. In the process of the microstructure preparation, a PDMA film is glued on a bidirectionally prestretched PDMS sheet that has a square distributed hole array on its surface. After releasing the prestrain, the film microstructure array is created spontaneously. The fabricated microstructures possess a spherical surface and demonstrate very good uniformity. The film microstructure arrays can serve as microlens arrays with a focal length of 1010 μm. The microstructure formation mechanism is investigated via theoretical analysis and numerical simulation. The simulation results agree well with the experimental results. The prestrain applied by mechanical stretching during the fabrication has an important effect on the shape of the resulting film microstructures. The microstructure geometry can be easily tuned through controlling the applied prestrain.

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We demonstrate polymer light-emitting diodes (LEDs) based on poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl] with end capper dimethylphenyl or N, N-bis(4-methylphenyl)-N-phenylamine. The introduction of end-capper groups increased the device luminance and efficiency, while greatly depressing the green emission. For the devices constructed of poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl] end capped with dimethylphenyl, the maximum luminance reached 381 cd/m 2 at 122 mA/cm 2 . The maximum external quantum efficiency was 0.16% at 117 mA/cm 2 , which is more than five times higher than that of the non-end-capped polymer LEDs. The electroluminescence (EL) maximum was at 485 nm, blue shifted by 52 nm with respect to that of the non-end-capped polyfluorene devices. It is proposed that efficient hole trapping at end capper and increased resistance of polyfluorene to oxidation are responsible for the improved device performance and color stability.

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