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We demonstrate that the optical absorption is enhanced in small molecule organic solar cells by using a trapezoid grating structure. The enhanced absorption is mainly attributed to both waveguide modes and surface plasmon modes, which is simulated by using finite-difference time-domain method. The simulated results show that the surface plasmon along the semitransparent metallic Ag anode is excited by introducing the periodical trapezoid gratings, which induce the increase of high intensity field in the donor layer. Meanwhile, the waveguide modes result in a high intensity field in acceptor layer. The increase of field improves the absorption of organic solar cells significantly, which is demonstrated by simulating the electrical properties. The simulated results also show that the short-circuit current is increased by 31% in an optimized device, which is supported by the experimental measurement. Experimental result shows that the power conversion efficiency of the grating sample is increased by 7.7%. [ABSTRACT FROM AUTHOR]

A localized plasmon resonance sensor consisting of an asymmetric split-ring resonator array sustaining highly localized field energy with high refractive index sensitivity and good figure of merit is demonstrated and investigated. In the proposed 3-cut split-ring resonator structure with broken symmetry, a highly tunable transmission with a large modulation depth and a narrow resonance linewidth is obtained, which shows polarization-insensitive and angle-independent properties. Numerical calculation results show that a high sensitivity of up to 1006 nm/RIU and a figure of merit of 9.7 can be reached. This plasmonic index sensor is practically obtainable, and is expected to have potential applications for high-sensitivity convenient and efficient detection. [ABSTRACT FROM AUTHOR]