Abstract
In this paper, we introduce hemiellipsoid- and inverted hemiellipsoid-modified semiconductor nanowire (NW) optical structures, and present a systematic investigation on light management of the corresponding arrays based on GaAs. It is found that the modification makes well utilization of light scattering and antireflection, thus leading to excellent light confinement with limited effective thickness. For example, 90% and 95% of the incident photons with the energy larger than the bandgap energy can be trapped by the inverted hemiellipsoid-modified NW arrays with the effective thicknesses of only ~ 180 and 270 nm, respectively. Moreover, excellent light confinement can be achieved in a broad range of the modification height. Compared to the corresponding array without top modification, spatial distribution of the photo-generated carriers is expanded, facilitating carrier collection especially for the planar pn junction configuration. Further investigation indicates that these composite nanostructures possess excellent omnidirectional light confinement, which is expected for advanced solar absorbers.
Highlights
Solar electricity based on the photovoltaic (PV) effect has made a remarkable progress in the past decades,and is gradually changing the global energy structure [1–10]
For the case of GaAs NW arrays, 90% and 95% of the incident photons with the energy larger than the bandgap energy can be trapped by the inverted hemiellipsoid-modified NW arrays with the effective thickness of ~ 180 and 270 nm
To more quantitatively compare light trapping of the optical systems, normalized theoretical photocurrent density, NJph, is adopted [27, 63], which is defined as the ratio of the theoretical photocurrent density of the investigated structure to that (~ 32.0 mA/cm2 at AM 1.5G [64] illumination for GaAs) of an ideal absorber with the same bandgap energy both at an internal quantum efficiency of 100%
Summary
Solar electricity based on the photovoltaic (PV) effect has made a remarkable progress in the past decades,and is gradually changing the global energy structure [1–10]. Thin film-based PV devices have the huge potential for material cost reduction, poor light absorption due to the limited optical thickness is a big concern and needs to be addressed by introducing light management structures, such as antireflection. Different from the traditional planar structures, nanostructured semiconductor solar absorbers possess superior properties in light management and photo-generated carrier collection and exhibit huge potential in application of high performance-to-cost optoelectronic devices including solar cells and photodetectors [28–36]. Each individual light management mode cannot fulfill efficient light confinement in a broad spectral range, especially for solar cell applications. Chen et al Nanoscale Research Letters (2018) 13:236 combination of different light management modes is necessary for full spectral absorption enhancement. Considering the concerns related to fabrication issues, e.g., high reproducibility at low cost, simple structure for light absorbers is required
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