Submicron periodic lattices are formed at the surface of phase-change-memory film materials based on the complex chalcogenide Ge_2Sb_2Te_5 when exposed to nanosecond laser pulses. The geometric characteristics and structural properties of laser-induced lattices are studied by optical and atomic-force microscopies and Raman spectroscopy. It is shown that, at appropriately chosen parameters of exposure to laser radiation, it is possible to implement periodic modulation of the refractive index in the structures formed. Modulation is due to the postexposure solidification of grating ridges and valleys in different phase states, whose dielectric constants widely differ from each other. In the vicinity of the maxima of the wavy structure, the amorphous state is mainly formed, whereas in the region of minima, the Ge_2Sb_2Te_5 structure corresponds mainly to the crystalline phase.
In this paper we showed that illumination of both front and back sides of heterojunction solar cells contribute efficiency. The obtained spectral dispersion of quantum efficiency confirms that contribution depends on conversion of short-wave photonts. The average difference between quantum efficiency of both sides is ∼ 11%. Under standard solar illumination in the 400−1100 nm wavelength range the short-current density for front side is 36.3 mA/cm² and 32.7 mA/cm² for back side with reduction about 10%.
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