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The valence band structures of a 35-nm-thick BaSi2 epitaxial film on Si(111) have been explored at room temperature by hard x-ray photoelectron spectroscopy (HAXPES). The experimentally obtained photoelectron spectrum is well reproduced by first-principles calculations based on the pseudopotential method. The top of the valence band consists mainly of Si 3s and 3p states in BaSi2, suggesting that the effective mass of holes is small in BaSi2. This is favorable from the viewpoint of solar cell applications. The observed spectrum shifted slightly to the lower energy side due to n-type conductivity of BaSi2. The valence band top was observed at about 0.8 eV below the Fermi level in the HAXPES spectrum. [ABSTRACT FROM AUTHOR]

The highest photoresponsivity and an internal quantum efficiency exceeding 70% at 1.55 eV were achieved for 400 nm thick undoped n-type BaSi2 epitaxial layers formed on a n+-BaSi2/p+-Si tunnel junction (TJ) on Si(111). The diffusion of Sb atoms was effectively suppressed by an intermediate polycrystalline Si layer grown by solid phase epitaxy, located between the TJ and undoped BaSi2 layers. [ABSTRACT FROM AUTHOR]

Nanopatterned poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layers fabricated by soft-nanoimprint were applied to CH3NH3PbBr3 (MAPbBr3) light-emitting diodes to enhance light extraction. The electric field distribution of MAPbBr3 devices with different periods of the nanopatterned PEDOT:PSS was calculated using the finite-difference time-domain method, demonstrating that the 400-nm period was more effective in improving light outcoupling. By integrating the nanopatterned PEDOT:PSS layer, the external quantum efficiency of the device increased from 6.5% to 10.3%. It can be attributed to the fact that the nanopatterned structure reduced the refractive index discontinuity at the interface between MAPbBr3 and PEDOT:PSS, thereby reducing light trapping in the waveguide mode. [ABSTRACT FROM AUTHOR]