A bandpass filter with twin wideband channels in a single-layer guided-mode resonance grating is presented. Strong refractive-index modulation is used to support the excitation of multimode resonances TEl,0, TEl,l, TE2,0, TEl,2, and TE2,1, which are excited by the first and second diffraction orders, relate asymmetrical line shapes and broad low-transmission bands, where TE is the transverse electric. Taking advantage of narrow linewidth and sharp edge line shape in the spectra of TE2,, （v is the mode）, a bandpass filter with form factors of 0.61 and 0.7 for long- and short-wave channels is presented to demonstrate this concept.
Dual-grating structure thin-film silicon solar cells with different front and back grating periodicities are designed The geometrical parameters of both gratings are investigated. The reflection is greatly reduced by the front grating, whereas the absorption in the long wavelength is increased because of the back grating. The short circuit current of the combined structure is enhanced by 16.8% for a 1μm thick c-Si layer compared with that of the conformal grating structure. The short circuit current can be further increased by creating a relative lateral displacement between the front and back gratings. The displacement results in a more remarkably enhaneed absorption when the thickness of the aetive layer is reduced, indicating its importance in the design of ultra-thin high-efficiency solar cells.
We present a new and practical approach for preparing submicro-textured silver and aluminum （Ag/Al） double-structured layers at low substrate temperatures. The surface texturing of silver and aluminum double-structured layers was performed by increasing the deposition temperature of the Al layers to 270℃. The highly submicro-textured silver and aluminum double-structured layers were prepared by thermal evaporation on quartz glasses and their surface microstructure, light scattering properties, and thermal stability were investigated. Results showed that the highly submicro-textured Ag/Al composite films prepared at low substrate temperatures used as back reflectors not only can enhance the light scattering and have good thermal stability, but also have good adhesion properties. In addition, their fabrication is low cost and readily carried out.
