Abstract
An ultra-broadband perfect absorber has a wide range of applications which include solar energy harvesting, imaging, photodetection etc. In this regard, InAs nanowire (NW) based structure is investigated in this work for achieving an ultra broadband perfect absorber. Finite difference time domain (FDTD) based numerical analysis has been performed to optimize the InAs nanowire based structure to obtain an efficient light absorber by varying different dimensional parameters. Mie theory and guided mode resonance based theoretical analysis is developed to validate the results and to get an insight into the tunability of the nanowire based structure. Moreover, the theoretical analysis elucidates the underlying physics of light absorption in nanowires. To achieve ultra broadband absorption, multi radii InAs nanowire based arrays are investigated and it is found that they exhibit superior performance compared to single radius NW based structures. The computed light absorption efficiency (LAE) and short circuit current density values are enhanced to 97% and 40.15 mA cm−2 at 10° angle of incidence for the optimized quad radii NW array within the wavelength range of 300 nm to 1000 nm and 300 nm to 1200 nm, respectively. Moreover, the absorption spectra for these structures are polarization independent and exhibit robust performance for varying angle of incidence. In addition, arrangement of the NW array (hexagonal or square) has negligible effect on the absorption spectra. Such ultra-broadband absorption capability of the proposed structure compared to existing works suggests that the InAs nanowire based structure is very promising as light absorber with prospects in the fields of photo detection, solar power generation, perfect cloaking, photochemistry and other thin film photonic devices.
Highlights
Ultra broadband perfect light absorbers has been a research attraction in recent times because of its vast eld of application like solar cells,[1] imaging,[2] photo detection,[3] shielding,[4] sensing,[5] optical data storage etc.[6]
The computed light absorption efficiency (LAE) and short circuit current density values are enhanced to 97% and 40.15 mA cmÀ2 at 10 angle of incidence for the optimized quad radii NW array within the wavelength range of 300 nm to 1000 nm and 300 nm to 1200 nm, respectively
Arrangement of the NW array has negligible effect on the absorption spectra. Such ultrabroadband absorption capability of the proposed structure compared to existing works suggests that the InAs nanowire based structure is very promising as light absorber with prospects in the fields of photo detection, solar power generation, perfect cloaking, photochemistry and other thin film photonic devices
Summary
Materials are widely used and fabrication technology is well established. The main goal of all the novel structures is to achieve improved absorption efficiency and in this regard nanowires (NWs) can be a promising candidate. We focus on InAs nanowire array based highly efficient absorber as it has large absorption coefficient in comparison to other semiconducting materials like silicon, GaAs or InP31 and yet to be explored extensively for ultra broadband absorber applications. Wu et al.[46] investigated the dependence of optical response on the InAs NW geometry and Rahman et al.[41] reported wavelength selective absorption in InAs NWs. Kupec et al worked on InP/ InAs NW based solar cells and analyzed the absorption characteristics of NW arrays of various diameters.[40] Though InAs nanowire fabrication is still challenging, wafer scale production of InAs nanowire has been reported.[47] In the present study, we have proposed InAs nanowire (NW) based structure for ultra broadband absorption of light and analyzed the absorption characteristics using guided mode resonance and Mie theory based theoretical framework and nite difference time domain (FDTD) based numerical technique. The analysis and discussions would give an intuitive perception behind the ultra broadband absorption characteristics of the optimized structure
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