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The effects of metal coating on the near-band-edge emission of ZnO thin films have been studied by photoluminescence and atomic force microscopy. Large enhancement in emission intensity has been observed from ZnO films when they are capped by Ag while negligible effect is seen on Au-coated films. In addition, the enhancement is found to increase with Ag thickness and the intensity eventually saturates at thickness of 200nm. By introducing MgO as a spacer between the metal coating and ZnO, the enhancement is shown to decrease with increasing the spacer thickness, which suggests the presence of the local fields induced by surface plasmons. As the emission energy of ZnO matches closely with the surface plasmon of Ag, it is speculated that the resonant coupling of the spontaneous emission in ZnO into the surface plasmons enhances the emission efficiency.

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We report on thermally evaporated chromium oxide (CrO x ) as cathode interfacial layer to improve the efficiency and stability in air for the bulk heterojunction solar cells of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Devices with CrO x interfacial layers show higher power conversion efficiency (PCE) and stability than those without interfacial layer. Devices with CrO x show improved stability more than 100 times that of devices without interfacial layer or with LiF interfacial layer. We tentatively attributed the CrO x interfacial layer as an electronic tunneling layer for electron collection and a protective layer of Al assumably by minimizing the organic−Al interfacial areas caused by the evaporation of Al and blocking diffusion of oxygen and water.

In this letter, we demonstrate that by blending insulating polymers, one can fabricate an insulating layer with controllable surface energy for organic field-effect transistors. As a model system, we used copper phthalocyanine evaporated on layers of polymethyl metacrylate blended with polystyrene with different blending ratios and measured the field-effect mobility in transistors. We show that the highest field-effect mobility is achieved for identical surface energies of the dielectric and the semiconductor. This simple technique demonstrates the viability of using the blends of insulating polymers to systematically control the surface energy of the gate dielectric toward achieving better performances.