Significant effects of cross term of Poynting vector on an electromagnetic wave propagation through a slab with low real part of impedance

Energy conversion and conservation for an electromagnetic wave traveling through a slab are analyzed. It is demonstrated that a cross term of Poynting vector may occur due to interference between forward and backward waves in the slab, and may play the leading role if the slab owns low real part of impedance. Several novel electromagnetic phenomena are predicted. For example, both reflection and transmission can be enhanced significantly even if the slab is made of lossy material. This work indicates that materials with low real part of impedance, like left-handed materials and near-zero-refractive-index materials, may hold unique electromagnetic properties and merit further exploration

Highly efficient ultrathin-film amorphous silicon solar cells on top of imprinted periodic nanodot arrays

The addressing of the light absorption and conversion efficiency is critical to the ultrathin-film hydrogenated amorphous silicon (a-Si:H) solar cells. We systematically investigate ultrathin a-Si:H solar cells with a 100 nm absorber on top of imprinted hexagonal nanodot arrays. Experimental evidences are demonstrated for not only notable silver nanodot arrays but also lower-cost ITO and Al:ZnO nanodot arrays. The measured external quantum efficiency is explained by the simulation results. The Jsc values are 12.1, 13.0, and 14.3 mA/cm2 and efficiencies are 6.6%, 7.5%, and 8.3% for ITO, Al:ZnO, and silver nanodot arrays, respectively. Simulated optical absorption distribution shows high light trapping within amorphous silicon layer