The characteristics of silicon nanowires (SiNWs) with surface roughness are reported and analyzed for solar cell (SC) applications. The SiNWs are fabricated using a metal-assisted chemical etching process. The effects of the etching time and reaction temperature on the surface roughness and the performance of the SiNWs are investigated. Further, the optical and electrical characteristics of the roughed NW SC are numerically studied and optimized using 3D finite difference time domain and finite element analysis, respectively. The numerically optimized SiNWs with surface roughness offer high optical ultimate efficiency (η) of 32.51% with an enhancement of 15.98% over the smoothed SiNW. This is due to the surface textures of the nanowires which produce multiple light scattering between the NWs’ walls. This will enhance the optical path length through the NW and enrich its light absorption. The doping level of the surface roughness of NWs with p-type/intrinsic/n-type (p-i-n) axial configurations is also simulated to compute the optoelectronic performance of the suggested design. The p-i-n axial doped design offers a power conversion efficiency of 14.92%, whereas the conventional NWs have a power conversion efficiency of 13.16%.
In this paper, a modified nanopyramid solar cell (SC) is introduced and numerically analyzed. The finite difference time domain (FDTD) method is used for computing the optical efficiency of the suggested design. The modified nanopyramid SC consists of an upper tapered nanopyramid part and lower nano-rectangular unit. The geometrical parameters of the proposed design are studied to maximize the optical absorption and hence the ultimate efficiency of the reported SC. The modified structure provides an optical ultimate efficiency and short circuit current density (Jsc) of 39.6 % and 32.4 mA/cm2 with improvement of 24.1% and 22.2 %, respectively over the conventional thin film (TF) nanopyramid SC. Further, the p-i-n axial junctions of the suggested SC exhibits open circuit voltage (Voc) of 0.57 volt, JSC of 28.42 mA/cm2 and power conversion efficiency (PCE) of 13.3% which are better than 0.559 volt, 19.6 mA/cm2 and 8.95%, respectively of the conventional nanopyramid TF-SC. This enhancement is mainly attributed to the combination between higher order modes generated by lower rectangle unit with lower order modes supported by the upper tapered nanopyramid.
Nowadays, the efficiency improvement of the silicon solar cells (SCs) is a hot research topic in photovoltaic industry. Silicon nanowires (Si-NWs) offer a promising candidate for low-cost SCs with high-efficiency due to their unique optical and electrical properties. The Si-NWs can achieve highly efficient light trapping with reduced cost. In this paper, a novel design of asymmetric tapered nanocone Si-NWs is introduced and analyzed by 3D finite difference time domain (FDTD) method. The particle swarm optimization (PSO) technique is also used to optimize the geometrical parameters of the suggested design to maximize the optical efficiency of the suggested SC. The asymmetric Si-NWs offer an ultimate efficiency of 39.6 % with an improvement of 24 % relative to the conventional symmetric nanocone Si-NWs.
In this paper, metallo-dielectric core-shell Yagi-Uda nanoantennas (NAs) are reported and optimized using 3D finite different time domain (FDTD) method and particle swarm optimization (PSO) technique to maximize the directivity. The suggested design has a silicon rectangular prism with spherical or rectangular silver core to improve the directivity and radiation efficiency. The proposed design with rectangular prism silver core achieves radiation efficiency of 77.23 % with a directivity of 18.41 at a wavelength of 500 nm. However, the directivity is increased to 21.22 with a radiation efficiency of 69.15 % with spherical-core based structure. The achieved enhancement is attributed to the elements shape in addition to the metallo-dielectric structure. Further, the silicon dielectric shell exhibits magnetic mode with high refractive index, as well as the surface plasmon mode supported by the silver core.
The optical characteristics of a star-shaped silicon nanowires (Si NWs) solar cell (SC) are numerically studied using three-dimensional (3-D) finite-difference time-domain (FDTD). The particle swarm optimization technique is used to optimize the geometrical parameters of the NW to maximize its light absorption. The optimized star-shaped Si NWs offer high ultimate efficiency (η) of 43.7% while its complementary design achieves η of 40.1%. This is due to the star surface textures that allow multiple light scattering between the NWs. This will increase the optical path length through the NW and improve its light absorption. The electrical properties of the proposed design are also calculated using the finite-element method. In this investigation, the doping level of the star-shaped Si NWs with p − i − n axial and radial configurations is simulated to quantify the optoelectronic performance of the reported design. The p − i − n axial doped design offers power conversion efficiency (PCE) of 21%; however, the p − i − n radial doping gives PCE of 21.3%. Therefore, the star-shaped design violates PCE of 17.3% and 15.9% of the conventional Si NWs with axial and radial doping, respectively.
In this study, the absorption capabilities of a plasmonic funnel-shaped silicon nanowire (SiNW) solar cell is introduced and analyzed by using 3D finite difference time domain method (FDTD). The reported NW design has titanium nitride (TiN) core as an alternative plasmonic material. The different geometrical parameters of the reported design are studied to maximize the absorption and hence the ultimate efficiency. An ultimate efficiency and short-circuit current density Jsc of 48.3% and 38.98 mA/cm2, respectively are obtained which are greater than the conventional Si-Funnel counterpart by 46.36%. The enhancement of the light absorption is attributed to the combination between different types of optical modes and plasmonics modes of the funnel-shaped NW and the TiN, respectively.
In this paper, new design of Yagi-Uda nano-antenna (NA) based on ellipsoid shape is introduced and numerically analyzed using 3-D finite difference time domain method (3-D FDTD) via Lumerical software package. The NA parameters are optimized using the particle swarm optimization (PSO) algorithm to achieve high directivity at a wavelength of 500 nm for wireless point-to-point applications. To illustrate the performance of the proposed antenna, different radiation parameters such as radiation pattern, directivity, and radiation efficiency have been studied. The optimized ellipsoid nano-antenna shows a directivity of 22.36 which is enhanced by 86.3 % relative to the conventional spherical counterpart. Moreover, the fabrication tolerance of the reported design is studied to ensure the accuracy of the introduced NA parameters to the fabrications errors.
KEYWORDS: Silicon, Absorption, Solar cells, Nanowires, Reflectors, Solar energy, Thin film solar cells, Finite-difference time-domain method, Silicon films, Antireflective coatings
A modified nanocone nanowire (NW) is proposed and analyzed for solar cell applications. The suggested NW consists of conical and truncated conical units. The geometrical parameters are studied by using 3D finite difference time domain (FDTD) method to achieve broadband absorption through the reported design and maximize its ultimate efficiency. The analyzed parameters are absorption spectra, ultimate efficiency and short circuit current density. The numerical results prove that the proposed structure is superior compared to cone, truncated cone and cylindrical nanowires (NWs). The reported design achieves an ultimate efficiency of 44.21% with an enhancement of 40.66% relative to the conventional conical NWs. Further, short circuit current density of 36.17 mA/cm2 is achieved by the suggested NW. The modified nanocone has advantages of broadband absorption enhancement, low cost and fabrication feasibility.
KEYWORDS: Silicon, Solar cells, Absorption, Finite-difference time-domain method, Nanowires, Doping, Thin film solar cells, Reflectors, Photons, Solar energy
Improving solar cell efficiency is a critical research topic. Nowadays, light trapping techniques are a promising way to enhance solar cell performance. A modified nanocone nanowire (NW) is proposed and analyzed for solar cell applications. The suggested NW consists of conical and truncated conical units. The geometrical parameters are studied using a three-dimensional (3-D) finite difference time-domain (FDTD) method to achieve broadband absorption through the reported design and maximize its ultimate efficiency. The analyzed parameters are absorption spectra, ultimate efficiency, and short circuit current density. The numerical results prove that the proposed structure is superior compared with cone, truncated cone, and cylindrical NWs. The reported design achieves an ultimate efficiency of 44.21% with substrate and back reflector. Further, short circuit current density of 36.17 mA / cm2 is achieved by the suggested NW. The electrical performance analysis of the proposed structure including doping concentration, junction thickness, and Shockley–Read–Hall recombination is also investigated. The electrical simulations show that a power conversion efficiency of 17.21% can be achieved using the proposed NW. The modified nanocone has advantages of broadband absorption enhancement, low cost, and fabrication feasibility.
KEYWORDS: Silicon, Surface roughness, Absorption, Nanowires, Solar cells, Finite-difference time-domain method, Solar energy, Communication engineering, Photovoltaics, Silicon films
Silicon nanowires (Si NWs) array have emerged as a promising route on the road to achieve highly efficient solar cells (SCs). The NWs SCs can achieve highly efficient light trapping with reduced cost and material usage. However, it is difficult to fabricate NWs with smoothed surfaces due to the deficiency in the fabrication process. The surface roughness of SCs is an essential parameter of the optoelectronic performance of these devices. In this paper, the effect of surface roughness on the optical and electrical performance of the NW SCs is reported and analyzed. The optical absorption and the generation rates are calculated using 3D finite difference time domain (FDTD) method while the electrical characteristics are calculated using finite element method via Lumerical device software package. In this investigation, short circuit current density, open circuit voltage and power conversion efficiency (PCE) are numerically studied to quantify the electrical performance of the reported structure. The simulation results show that the Si NWs with 10% surface roughness has higher PCE than smoothed Si NWs counterpart by 8.33%. This is due to the multiple scattering between the SiNWs which increases the light absorption and hence the PCE.
The electrical characteristics of funnel-shaped silicon nanowire (SiNW) solar cells are introduced and numerically analyzed. The funnel-shaped NW consists of a cylinder over a conical unit. Its aim is to maximize the optical absorption over a large wavelength range and hence the electrical efficiency by increasing the number of resonance wavelengths or by enlarging the resonance wavelength range. The conical part has different radii in the axial direction, which increases the number of resonance wavelengths. Further, the coupling between the supported modes by the upper cylinder and the lower tapered cone offers multiple optical resonances required for broadband absorption. The optical characteristics and generation rates through the studied design are obtained using 3-D finite difference time domain. However, the electrical properties are calculated using finite element via the Lumerical device software package. In this regard, radial and axial junctions are examined for the suggested design and compared with the conventional cylindrical SiNW counterpart. In this investigation, short circuit current density, open circuit voltage, fill factor, and power conversion efficiency (PCE) are simulated to quantify the optoelectronic performance of the reported design. Furthermore, the effects of the doping concentration and carrier lifetime on the performance of the funnel-shaped design are reported. The proposed SiNWs offer PCE and short circuit density of 12.7% and 27.6 mA/cm2, respectively, for the axial junction. However, the funnel design with core–shell junction shows an efficiency and short-circuit current (Jsc) of 14.13% and 31.94 mA/cm2, respectively. Therefore, the suggested design has higher efficiency than 6.4% and 9.6% of the conventional cylindrical SiNWs according to the axial and core shell junctions, respectively.
An approach to enhance the ultimate efficiency of the silicon nanowires (Si NWs) solar cell is proposed based on a hybrid population-based algorithm. The suggested technique integrates the ability of exploration in a gravitational search algorithm (GSA) with the exploitation capability of particle swarm optimization (PSO) to synthesize both algorithms’ strengths. The hybrid GSA-PSO algorithm in MATLAB® code is linked to finite-difference time-domain solution technique based on Lumerical-software to simulate and optimize the Si NWs’ geometrical parameters. The suggested GSA-PSO algorithm has advantages in terms of better convergence and final fitness values than that of the PSO algorithm. Further, the Si NWs lattice with optimized diameters and heights shows a high ultimate efficiency of 42.5% with an improvement of 42.8% over the Si NWs lattice with the same diameters and heights. This enhancement is attributed to the different generated optical modes combined with multiple scattering and reduced reflection due to the different heights and different diameters, respectively.
KEYWORDS: Absorption, Solar cells, Silicon, Finite-difference time-domain method, Solar energy, Energy efficiency, Communication engineering, Optical engineering, Semiconductors, Nanowires
Silicon nanowires (SiNWs) are the subject of intense research in solar energy harvesting due to their unique electrical and optical characteristics. The transmission, reflection, and absorption spectra of decagonal Si NWs (D-SiNWs) solar cells have been calculated using a three-dimensional finite-difference time-domain method to present a design guideline for ultra-high efficiency SiNW in solar cell applications. In this study, the structure geometrical parameters of the suggested design are tuned to maximize light absorption. The ultimate efficiency is used to quantify the absorption enhancement of the SiNWs solar cells. A maximum ultimate efficiency of 39.3% is achieved for the reported D-SiNWs, which is greater than that of the previous work of slanting Si NWs by 17.49%.
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