Extreme Light Absorption in Thin Semiconductor Films Wrapped around Metal Nanowires

Abstract

Metallic and dielectric nanostructures have highly tunable resonances that have been used to increase light absorption in a variety of photovoltaic materials and device structures. Metal nanowires have also emerged as a promising candidate for high-performance transparent electrodes for local contacts. In this Letter we propose combining these electrical and optical functions. As a first step, we use rigorous solutions to Maxwell's equations to demonstrate theoretically extreme absorption in semiconductor thin films wrapped around metal nanowires. We show that there are two key principles underlying this extraordinary light trapping effect: (1) maximizing the absorption of each individual resonance by ensuring it is critically coupled and (2) increasing the total number of degenerate resonances. Inserting a metal core into a semiconductor nanowire creates such a degeneracy: polarization-dependent Mie resonances are transformed into polarization-independent Fabry-Pérot-like resonances. We demonstrate that, by reducing the polarization sensitivity and increasing the number of critically coupled modes, this hybrid coaxial nanowire geometry substantially outperforms solid semiconducting nanowires, even though the semiconductor volume is significantly reduced. These results suggest that metal nanowires with semiconductor shells might be ideal building blocks for photovoltaic and solar fuel applications.

Physical Modeling of Photoelectrochemical Hydrogen Production Devices

“…The most recent development was the construction of a device capable of unassisted solar water splitting (Figure 3), but the achieved efficiency was very low 28 . However, the operating principles of the wire array PE or PV such as charge transport 37 , optical properties [38][39][40] , mass transport in the electrolyte inside the array 41 48,49 and TiO2 50 have also been studied.…”

“…Also, the optical properties of water have often been neglected, even though they can affect the device operation noticeably 61 . When detailed optical models have been used their purpose has been to explore possibilities for device optimization specifically by optical design 23,39 .…”

Au-Cu2O core-shell nanowire photovoltaics

“…22,23,31 The metal-semiconductor core-shell structure can lead to even higher absorption, while further reducing the amount of semiconductor. 32 Several research groups have already utilized metal-semiconductor core-shell nanospheres or rods for plasmon mediated charge carrier dynamics for photovoltaics and photocatalysis. In these examples, however, semiconductor materials were not used for the visible light absorption or materials were suspended completely in solution.…”

Selective radiative heating of nanostructures using hyperbolic metamaterials

“…Physically, the single-channel limit is achieved when radiative damping and absorptive loss both contribute equally to the absorption efficiency of the mode [44][45][46]. Mathematically, from Eq.…”