Ultrathin Silicon Solar Cells Research Articles

Free-standing ultrathin silicon wafers and solar cells through edges reinforcement

Crystalline silicon solar cells with regular rigidity characteristics dominate the photovoltaic market, while lightweight and flexible thin crystalline silicon solar cells with significant market potential have not yet been widely developed. This is mainly caused by the brittleness of silicon wafers and the lack of a solution that can well address the high breakage rate during thin solar cells fabrication. Here, we present a thin silicon with reinforced ring (TSRR) structure, which is successfully used to prepare free-standing 4.7-μm 4-inch silicon wafers. Experiments and simulations of mechanical properties for both TSRR and conventional thin silicon structures confirm the supporting role of reinforced ring, which can share stress throughout the solar cell preparation and thus suppressing breakage rate. Furthermore, with the help of TSRR structure, an efficiency of 20.33% (certified 20.05%) is achieved on 28-μm silicon solar cell with a breakage rate of ~0%. Combining the simulations of optoelectrical properties for TSRR solar cell, the results indicate high efficiency can be realized by TSRR structure with a suitable width of the ring. Finally, we prepare 50 ~ 60-μm textured 182 × 182 mm2 TSRR wafers and perform key manufacturing processes, confirming the industrial compatibility of the TSRR method.

Influence of Photonics and Plasmonics Effect on Ultrathin Amorphous Silicon Thin Film Solar Cell

Abstract Our recent surge in silicon derived materials has major demand in thin film photovoltaic (PV) modules and enhancing the significant numbers. The rigorous coupled wave analysis method is a simple and fast method also known as developed to determine the light absorption and cell efficiency. The optics of thin film solar cells (amorphous silicon) garnering crucial role in the photovoltaic market. In this work, an ultrathin thin film amorphous silicon solar cell PV performance investigated by periodically textured surfaces at the nanoscale level. This analysis of periodic textured substrate was deriving optimal surface textures. The nanogratings lead to light scattering mechanism with the higher order diffraction angle and enhanced the light absorption of the incidence spectrum. The influence of grating period and height, the collection of the charge carriers increased at various wavelengths from ultraviolet, visible and infrared spectral regions are discussed with the assistance of photonic and plasmonic modes. Finally, nanoscale engineering mechanism the optimized thin film amorphous silicon solar cell yielded the highest current densities (22.6 and 23.8 mA/cm2) in both polarization modes.

Radiation effects model for Ultra-Thin Silicon Solar Cells

This work is focused on investigation of radiation effects in Ultra-Thin Silicon solar cells with a particular emphasis on electron irradiation. The study is motivated by the application of these solar cells, developed by Solestial, Inc., for powering space missions, including those led by NASA, the Department Of Defence (DOD), and commercial satellite missions. Our research encompasses both experimental and theoretical approaches, addressing unique challenges posed by ultra-thin solar cell technology that deviates from the traditional models. From the experimental point of view, the test structures were irradiated with 1 MeV electrons up to the fluence of 1E+15 e/cm 2. Radiation effects due to accumulated electron dose were noticed as a drop in open-circuit voltage (Voc ). An analytical expression for modeling the Voc characteristic of the UT-Si cell after exposure to electron irradiation was formulated and subsequently compared with experimental data. The theoretical foundation of the proposed approach builds upon the Non-Ionising Energy Loss (NIEL) concept, a fundamental parameter in addressing radiation damage modelling and survivability predictions.

Plasmonic enhanced ultra-thin solar cell: A combined approach using fractal and nano-antenna structure to maximize absorption

In this study, a combined structure is proposed to develop ultra-thin silicon solar cells. This integrated structure consists of silver fractal-like nano-particles and leaky wave nanoantennas. The nano-cuboid pattern embedded inside anti-reflective coating benefits from different optical modes, such as surface plasmons and cavity modes, which trap more light and amplify the electric field in the upper region of the absorber layer. On the bottom side, the hybrid plasmonic mode in the structure of the optical nanoantenna makes it possible to focus and direct the incoming light on the bottom of the absorber layer and increase the optical pathlengths in the ultra-thin film solar cell. The nanoantenna behavior and three-dimensional finite-difference time-domain analysis show that photon absorptions improve significantly at long wavelength lightwaves through this proposed combined structure. The short circuit current enhancement of the solar cell under 1 sun standard illumination is obtained by a factor of 1.94 and 1.80 for TM and TE polarization of incident light, respectively. Due to the acceptable results for different incident angles and polarizations, ultra-thin thickness, and nano-cuboids synthesis feasibility, our structure has the potential to be applied in the design of miniaturized photovoltaic devices.

Plasmon-enhanced parabolic nanostructures for broadband absorption in ultra-thin crystalline Si solar cells.

Sub-wavelength plasmonic light trapping nanostructures are promising candidates for achieving enhanced broadband absorption in ultra-thin silicon (Si) solar cells. In this work, we use finite-difference time-domain (FDTD) simulations to demonstrate the light harvesting properties of periodic and parabola shaped Si nanostructures, decorated with metallic gold (Au) nanoparticles (NPs). The active medium of absorption is a 2 μm thick crystalline-silicon (c-Si), on top of which the parabolic nanotextures couple incident sunlight into guided modes. The parabola shape provides a graded refractive index profile and high diffraction efficiencies at higher order modes leading to excellent antireflection effects. The Au NPs scatter light into the Si layer and offer strong localized surface plasmon resonance (LSPR) resulting in broadband absorption with high conversion efficiency. For wavelengths (λ) ranging between 300 nm and 1600 nm, the structure is optimized for maximum absorption by adjusting the geometry and periodicity of the nanostructures and the size of the Au NPs. For parabola coated with 40 nm Au NPs, the average absorption enhancements are 7% (between λ = 300 nm and 1600 nm) and 28% (between λ = 800 nm and 1600 nm) when compared with bare parabola. Furthermore, device simulations show that the proposed solar cell can achieve a power conversion efficiency (PCE) as high as 21.39%, paving the way for the next generation of highly efficient, ultra-thin and low-cost Si solar cells.

Ultrathin Film Amorphous Silicon Solar Cell Performance using Rigorous Coupled Wave Analysis Method

The issues related to global energy needs and environmental safeties as well as health crisis are some of the major challenges faced by the human, which make us to generate new pollution-free and sustainable energy sources. For that the optical functional nanostructures can be manipulated the confined light at the nanoscale level. These characteristics are emerging and leading candidate for the solar energy conversion. The combination of photonic (dielectric) and plasmonic (metallic) nanostructures are responsible for the development of better optical performance in solar cells. Here, the enhancement of light trapping within the thin active region is the primary goal. In this work, we have studied the influence of front-ITO (rectangular) and back-Ag (triangular) nanogratings were incorporated with ultrathin film amorphous silicon (a-Si) solar cell by using rigorous coupled wave analysis (RCWA) method. The improvement of light absorption, scattering (large angle), diffraction and field distributions (TE/TM) were demonstrated by the addition of single and dual nanogratings structures. Significantly, the plasmonic (noble metal) nanogratings are located at the bottom of the cell structure as a backside reflector which is helpful for the omni-directional reflection and increased the path length (life time) of the photons due to that the collection of the charge carriers were enhanced. Further, the proposed solar cell structure has optimized and compared to a back-Ag, front-ITO and dual nanogratings based ultrathin film amorphous silicon solar cell. Finally, the obtained results were evidenced for the assistance of photonic and plasmonic modes and achieved the highest current density (Jsc) of 23.82 mA/cm2(TE) and 22.75 mA/cm2 (TM) with in 50 nm thin active layers by integration of (dual) cell structures.

Optimization of light absorption in ultrathin elliptical silicon nanowire arrays for solar cell applications

The present study proposes an elliptical silicon array for broadband absorption inside ultra-thin silicon solar cells (SCs). The simulation results suggest that breaking the arrangement of the nanowires (NWs) modifies the absorption intensities. The efficient design of irregular NWs can contribute to improved absorption of such structures in comparison with ordinary structures. Single elliptical NWs exert significant optical antenna effects, which enable higher absorption of particular frequencies. However, in the case of NW arrays enhanced absorption is the outcome of trade off between an optical antenna and diffraction effects. In this study, a structure composed of a semi-periodic NW is suggested which can achieve improved performance in ultra-thin silicon SCs.

Performance improvement of an ultra-thin amorphous silicon solar cell using multilayers chirped diffraction back gratings

In this paper, a systematic design of a novel back reflector using chirped grating structures is investigated for thin-film amorphous silicon (a-Si) solar cells. At first, a cell with an optimum ITO antireflecting layer is simulated and a photocurrent of 17.67 mA cm−2 is obtained. Then a conventional grating from SiO2 is evaluated and the maximum photocurrent of 18.97 mA cm−2 is calculated. Then a thin-film solar cell based on the chirped back grating is designed and the photocurrent is increased to 19.30 mA cm−2. Also, their integrated optical absorption is compared for better understanding. To give a numerical comparison of the cells with a different number of chirped grating layers, a short circuit current for different numbers of grating layers is analyzed. It is shown that maximum current density is obtained for 5 layers grating with the chirped coefficient length of near 20 nm. It is believed that chirped back grating can be used to design higher performance thin film a-Si solar cells and the results are helpful for photovoltaic applications.

The role of photonic and plasmonic modes in ultrathin amorphous silicon solar cells using finite difference time domain method

In photovoltaic market, the enhancement of optical performance in an ultra-thin film amorphous silicon (a-Si) solar cell is significant. Our main objective is to design and simulate a highest current density by using various nanostructures integrated with ultrathin a-Si solar cells. In this proposed work, the various photonic and plasmonic nanostructures were used in front side of the absorber layer and enhanced the collection of charge carriers due to that an improved the current density in ultrathin a-Si solar cells. Using finite-difference time-domain (FDTD) method, the obtained results indicate the optimized SiO2 nanogratings and Si3N4 thin films acting as an anti-reflection coating (ARC) layer with air medium (AM1.5) which showed significant current density of 16.25 mA/cm2 in ultra-thin a-Si solar cells. Finally, the light trapping mechanism evidenced the importance of nanostructures using transverse electric (TE) and magnetic (TM) field distributions by changing the various incident wavelength.

Ultrathin Bifacial Passivated Emitter and Rear Cell with Inverted Pyramid Textures

Wafer thinning is a crucial technique for high‐efficiency solar cells. Herein, an inverted pyramid (IP) texture is prepared on a 35 μm‐thick flexible silicon (Si) wafer with a standard area of 156 × 156 mm2. Based on the experimental results, an ultrathin bifacial passivated emitter and rear cell (PERC) with IP textures using PC1D simulation is designed. The influence of wafer thickness, IP texture, bifacial structure, thickness of the antireflection coating, and doping concentration on device performance is investigated. The results show that the ultrathin IP‐based bifacial PERC possesses better output performance than the traditional cell. Finally, a simulated maximum efficiency of 23.44% is obtained using PC1D software, with an open‐circuit voltage of 0.7127 V and a short‐circuit current of 9.272 A. This ultrathin PERC with IP textures provides an effective way to improve the efficiency of ultrathin silicon solar cells.

Fourteen percent efficiency ultrathin silicon solar cells with improved infrared light management enabled by hole‐selective transition metal oxide full‐area rear passivating contacts

AbstractThe present study investigates the application of hole‐selective transition metal oxide (TMO) layers (MoOx, V2Ox, and WOx) with silver (Ag) as full‐area rear contact to 22.5 μm‐thick low‐quality Cz p‐type c‐Si solar cells. Thin films of metal oxides are deposited directly on p‐type c‐Si by thermal evaporation at room temperature. The large work function of these TMOs creates strong accumulation at the interface with p‐type c‐Si, which allows only holes to transport and simultaneously suppress the interfacial recombination current density (J0) and contact resistivity (ρc). The current generation and losses of 22.5 μm‐thick solar cells with different hole‐selective TMO/Ag at the rear are simulated. The presence of TMO/Ag at the rear is found to significantly reduce parasitic light absorption at longer wavelengths which becomes more pronounced for ultrathin wafers, providing significant advantages over conventional Al contact. The best device performance was attained by the MoOx/p‐type c‐Si solar cells, demonstrating a considerably high efficiency (η) of 14% with Voc of 555 mV, FF of 76.0%, and Jsc of 33.2 mA/cm2. Furthermore, the present work is the first to employ MoOx, V2Ox, and WOx as rear contact in ultrathin p‐type c‐Si solar cells.

Study of ultrathin‐film amorphous silicon solar cell performance using photonic and plasmonic nanostructure

The photonic and plasmonic nanostructures are highly feasible for enhanced light trapping mechanisms. These nanostructures hold great promises for better photovoltaic performance by yielding the highest light-harvesting photons within the few nanometer absorber regions. The shed light on the nano-scaled structures (thin films and nanogratings) is responsible for the highest scattering mechanism with the omnidirectional diffraction angles and enhanced life time of the photons. In this research work, we have focused on improved ultrathin film amorphous silicon (a-Si) solar cell performance, which was integrated by top-SiO2 and bottom-Ag nanogratings as a backside reflector by using rigorous coupled-wave analysis method. The SiO2 antireflection coating, nanogratings, and absorber (a-Si) layer thicknesses were optimized for better photovoltaic performance. With the influence of optimization parameters, the highest current density of 27.03 and 33.53 mA/cm2 were obtained from transverse electric and transverse magnetic polarization conditions due to the surface guided-mode, Fabry–Perot resonance, surface excitation, localized fields, and surface plasmon polariton modes.

Light-harvesting enhancement in ultrathin film silicon solar cells using photonic and plasmonic nanostructures

Past few decades, nanostructures are useful in the active region and light-harvesting layers in thin film solar cells. In this work, the high reflectance alternative Si/SiO2 distributed Bragg reflectors (DBRs), and aluminum (Al) thin film layers were integrated as a backside reflectors in ultrathin film silicon solar cells to improve the light trapping mechanism using finite-difference time-domain (FDTD) method. DBR is known as one-dimensional photonic crystal (1DPC) used as backside reflectors with the addition of SiO2 buffer layer. Further, the transverse electric (TE) and magnetic (TM) field distribution shown the strong light scattering in the silicon active layer region by integration of top (ITO) and bottom (Al) nanogratings. Both polarization conditions yielded the highest current density (Jsc) of 22.03 (TE) and 30.42 mA/cm2 (TM) achieved within 50 nm active region thickness.

Photocurrent improvement of an ultra-thin silicon solar cell using cascaded cylindrical shape plasmonic nanoparticles

The main aim of this research work is to significantly improve the photocurrent of an ultra-thin silicon solar cell. Here, cylindrical shape cascaded plasmonic nanoparticles are used to design an ultra-thin silicon solar cell. The main idea is to manipulate the absorption spectra of a thin absorber by applying four cascaded cylindrical shape nanoparticles from different materials with different radii and heights. At first, a cell with one nanoparticle at the surface and another one with a nanoparticle at the bottom side are simulated, and their photocurrents are determined. Then, a cell with four cascaded Ag, Al, Ag-Al, and Al-Ag nanoparticles is simulated. The maximum photocurrent density and efficiency of 23.46 mA cm−2 and 13.95%, respectively, are obtained for a cell in which Ag and Al’s nanoparticles are used alternatively from top to bottom. The photocurrent density is 8.2 mA cm−2 for a cell without any nanoparticles. The simulated results show that cascaded nanoparticles significantly enhance the photocurrent. Finally, the generation rate is presented at different wavelengths.

Efficiency enhancement of an ultra-thin film silicon solar cell using conical-shaped nanoparticles: similar to superposition (top, middle, and bottom)

The use of conical-shaped plasmonic nanostructures for light management in an ultra-thin silicon solar cell has been investigated. The optical absorption and hence photocurrent are obtained for several cases of structures using finite difference time domain simulations. In this paper, we demonstrate that the use of superposition theorem causes significant photocurrent enhancement due to the surface plasmonic effects of nanoparticles. For this, at first, we used one conical-shaped nanoparticle at the top side, then in the rear side, and finally, three nanoparticles are used in the top, bottom, and middle sides. Depending on the incident light wavelength, each nanoparticle manipulates the part of the spectrum. The photocurrents of 9.165, 10.463, 16.402, 17.761, and 18.072 mA/cm2, are obtained for a cell without nanoparticles, with one conical-shaped NP at the top, with one conical-shaped NP at the bottom, with two NPs at top and bottom and with three NPs at the top, bottom, and middle, respectively. Finally, the electrical field distribution and generation rate are calculated for proposed structures.

Photocurrent improvement of an ultra-thin silicon solar cell using the localized surface plasmonic effect of clustering nanoparticles

The cluster-shaped plasmonic nanostructures are used to manage the incident light inside an ultra-thin silicon solar cell. Here we simulate spherical, conical, pyramidal, and cylindrical nanoparticles in a form of a cluster at the rear side of a thin silicon cell, using the finite difference time domain (FDTD) method. By calculating the optical absorption and hence the photocurrent, it is shown that the clustering of nanoparticles significantly improves them. The photocurrent enhancement is the result of the plasmonic effects of clustering the nanoparticles. For comparison, first a cell with a single nanoparticle at the rear side is evaluated. Then four smaller nanoparticles are put around it to make a cluster. The photocurrents of 20.478 mA/cm2, 23.186 mA/cm2, 21.427 mA/cm2, and 21.243 mA/cm2 are obtained for the cells using clustering conical, spherical, pyramidal, cylindrical NPs at the backside, respectively. These values are 13.987 mA/cm2, 16.901 mA/cm2, 16.507 mA/cm2, 17.926 mA/cm2 for the cell with one conical, spherical, pyramidal, cylindrical NPs at the backside, respectively. Therefore, clustering can significantly improve the photocurrents. Finally, the distribution of the electric field and the generation rate for the proposed structures are calculated.

Optical pathlength enhancement in ultrathin silicon solar cell using decorated silver nanoparticles on aluminium grating

Optical pathlength enhancement in ultrathin silicon solar cell using decorated silver nanoparticles on aluminium grating

Sidewall Profile Dependent Nanostructured Ultrathin Solar Cells With Enhanced Light Trapping Capabilities

Theoretical studies of ultra-thin silicon solar cells with cylindrical, conical and parabolic surface nanostructures inherited from natural self-assembled anodic alumina oxide (NSA-AAO) were performed by finite-difference time-domain (FDTD) method. All nanostructured solar cells obtained an optimized efficiency enhancement as high as more than 33% comparing with that of the anti-reflective (AR) one. Numerical results reveal that the range of efficient structural parameters for the nanostructured (e.g., cylindrical) solar cell can be effectively enlarged as the period of the nanostructure changes from 0.1 μm to 0.5 μm. Moreover, the improvements of absorption photocurrent density (Jph) in conical and parabolic nanostructured solar cells are comparable with the cylindrical nanostructured one but less sensitive to the fill factor and structural height in the whole simulation region of 0.1–0.9 and 0–0.25 μm, respectively. Equivalent refractive index models were used to analysis the antireflection performance of surface nanostructures from the point of view of sidewall profiles. Resonance modes induced through nanostructures have greatly improved the absorptance of solar cells in broadening wavelength bands which consequently raised the Jph. This study serves as a way for the practical design and application of AAO nanostructure based high-efficiency ultra-thin solar cells.

Design of an ultra-thin silicon solar cell using Localized Surface Plasmonic effects of embedded paired nanoparticles

The demand for cheaper and more efficient solar cells is the main reason behind the ongoing research on ultra-thin solar cells. In this research work, the electric field generated by the surface plasmons effects has been used to design an ultra-thin silicon solar cell. The main idea of this work is the use of paired nanoparticles with both the same and different radiuses. At first, a cell with one nanoparticle in embedded and non-embedded forms is designed and photocurrents of 11.52 and 20.87 mA/cm2 are obtained, respectively. In the case of paired nanoparticles, the photocurrents of 11.9 and 21.68 mA/cm2 are obtained for embedded and non-embedded cases, respectively. These values are 11.89 and 21.84 mA/cm2 for paired nanoparticles with different radiuses. Our simulated results show that embedded nanoparticles significantly improve the photocurrent of an ultra-thin silicon solar cell. This approach and obtained results are applicable to various cell, thicknesses, and shapes of nanoparticles.

Controllable fabrication and mechanism study of textured ultra-thin silicon wafers via one-step Cu-assisted chemical etching

In this paper, the one-step Cu-assisted chemical etching method is reported for controllable thinning and texturization on mono-crystalline silicon in Cu2+/HF/H2O2 mixture solution. HF and Cu2+ exhibited a synergetic effect on accelerating etching process while H2O2 slowed down the preferential Si (100) etching by oxidizing the Cu atoms. Within optimal 0.15 M Cu2+/4 M HF/0.88 M H2O2 solution, quasi-inverted pyramid-like structures of 2–4 μm in size and a reflectance of 8.46% were obtained at 20 °C. By adjusting the temperature and etching time, ultra-thin silicon wafers with thickness of 19–120 μm were fabricated. Comparing the microstructures obtained at 20 °C and 60 °C, widths and inclination angles were distinct. By illustrating the transportation and distribution of holes during the etching process, the intrinsic connection between thinning and texturization was studied. The etching results, including etching rates and morphologies, were determined by the distribution of holes between the B’ and B” orbitals. In summary, controllable fabrication of textured ultra-thin silicon wafers with desired thickness and microstructures could be achieved by one-step, short-time and low-temperature Cu-assisted chemical etching method, exhibiting a great potential use in ultra-thin silicon solar cells.