Improved efficiency of ZnSe QDs—Si hybrid solar cell system by down shifting process

Abstract

Traditional Si solar cells have a narrow active absorption cross section among the short wavelength range (200–400 nm). The down-shifting process can efficiently improve the spectral response of Si solar cells by converting shorter wavelengths (i.e., ultraviolet, UV) to longer wavelengths (i.e., the visible range). Here, ZnSe quantum dots (QDs), prepared by an aqueous solution method and employed as a luminescent down-shifting layer, were spin coated onto the upper surface of manufactured Si solar cells. Measurements under standard test conditions (AM1.5, 100 mW/cm2) show that the efficiency of the ZnSe QDs–Si hybrid solar cell is increased from 11.48% to12%. The improvement of the ZnSe QDs–Si hybrid solar cell is ascribed to the efficient down-shifting process of ZnSe QDs, which enhances spectra response in the UV region for Si solar cells. The mechanism of this optical coupling and efficiency enhancement is investigated in detail. These results support the case that low-cost ZnSe QDs can be employed as efficient down-shifting material on large-area solar cells.