Abstract
The absorption properties of ZnO nanowire arrays covered with a semiconducting absorbing shell for extremely thin absorber solar cells are theoretically investigated by optical computations of the ideal short-circuit current density with three-dimensional rigorous coupled wave analysis. The effects of nanowire geometrical dimensions on the light trapping and absorption properties are reported through a comprehensive optical mode analysis. It is shown that the high absorptance of these heterostructures is driven by two different regimes originating from the combination of individual nanowire effects and nanowire arrangement effects. In the short wavelength regime, the absorptance is likely dominated by optical modes efficiently coupled with the incident light and interacting with the nearby nanowires (i.e. diffraction), induced by the period of core shell ZnO nanowire arrays. In contrast, in the long wavelength regime, the absorptance is governed by key optically guided modes, related to the diameter of individual core shell ZnO nanowires.
Highlights
Over the last decade, increasing interest has been devoted to core shell nanowire (NW)-based solar cells [1,2,3,4] due to their ability to achieve high absorption and low-reflection, as well as to efficiently separate and collect photo-generated charge carriers
The physical mechanisms responsible for light absorption have been numerically investigated by 3D rigorous coupled wave analysis (RCWA) in a novel class of core shell NW-based solar cells involving ZnO NWs covered with a semiconducting absorbing shell
Thanks to RCWA which gives access to the modal behaviour of the structure, the absorption has been analysed through optical modes for two representative sets of geometrical dimensions
Summary
Over the last decade, increasing interest has been devoted to core shell nanowire (NW)-based solar cells [1,2,3,4] due to their ability to achieve high absorption and low-reflection, as well as to efficiently separate and collect photo-generated charge carriers. When ZnO NW arrays are covered with an extremely thin absorber (ETA) semiconducting absorbing shell, the so-called ETA solar cells based on core shell ZnO NW heterostructures can reach photoconversion efficiency as high as 4.74% [18]. The type II band alignment between ZnO NWs and the semiconducting absorbing shell is expected to efficiently separate photo-generated charge carriers without any required doping
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