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In this paper, a novel design of tapered dipole nanoantenna is introduced and numerically analyzed for energy harvesting applications. The proposed design consists of three steps tapered dipole nanoantenna with rectangular shape. Full systematic analysis is carried out where the antenna impedance, return loss, harvesting efficiency and field confinement are calculated using 3D finite element frequency domain method (3D-FEFD). The structure geometrical parameters are optimized using particle swarm algorithm (PSO) to improve the harvesting efficiency and reduce the return loss at wavelength of 500 nm. A harvesting efficiency of 55.3% is achieved which is higher than that of conventional dipole counterpart by 29%. This enhancement is attributed to the high field confinement in the dipole gap as a result of multiple tips created in the nanoantenna design. Furthermore, the antenna input impedance is tuned to match a wide range of fabricated diode based upon the multi-resonance characteristic of the proposed structure.

In this Letter, funnel-shaped silicon nanowires (SiNWs) are newly introduced for highly efficient light trapping. The proposed designs of nanowires are inspired by the funnel shape, which enhances the light trapping with reduced reflections in the wavelength range from 300 to 1100 nm. Composed of both cylindrical and conical units, the funnel nanowires increase the number of leaky mode resonances, yielding an absorption enhancement relative to a uniform nanowire array. The optical properties of the suggested nanowires have been numerically investigated using the 3D finite difference time domain (FDTD) method and compared to cylindrical and conical counterparts. The structural geometrical parameters are studied to maximize the ultimate efficiency and hence the short-circuit current. Carefully engineered structure geometry is shown to yield improved light absorption useful for solar cell applications. The proposed funnel-shaped SiNWs offer an ultimate efficiency of 41.8%, with an enhancement of 54.8% relative to conventional cylindrical SiNWs. Additionally, short-circuit current of 34.2  mA/cm2 is achieved using the suggested design.

In recent years, newly emerging photovoltaic (PV) devices based on silicon nanowire solar cells (SiNW-SCs) have attracted considerable research attention. This is due to their efficient light-trapping capability and large carrier transportation and collection with compact size. However, there is a strong desire to find effective strategies to provide high and wideband optical absorption. In this paper, a modified circular nanowire (NW) with a nanocrescent hole is newly introduced and analyzed for solar cell applications. The crescent hole can strongly improve the light absorption through the NW due to the excitation of numbers of modes that can be coupled with the incident light. The material index, volume, and position of the nanohole are studied to significantly increase the optical absorption efficiency and hence the power conversion efficiency (PCE). The absorption performance can be further preserved by using a silicon substrate due to the coupling between the supported modes by the NW, and that of the substrate. The optical and electrical characteristics of the suggested design are investigated using finite difference time domain and finite element methods via Lumerical software packages. The reported asymmetric design offers higher optical and electrical efficiencies compared to the conventional NW counterpart. The proposed NW offers a short circuit current density (Jsc) of 33.85 (34.35) mA/cm2 and power conversion efficiency (PCE) of 16.78 (17.05) % with an enhancement of 16.3 (16.8) % and 17.3 (18.4) % for transverse magnetic (TM) and transverse electric (TE) polarizations, respectively, compared to the conventional cylindrical counterpart.

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