Surface Of Silicon Solar Cells Research Articles

Silver cementation mechanism for leaching silicon solar cells in nitric acid

Silicon solar panels are often overlooked in e-waste recycling technology, even though they contain precious silver (Ag). In order to help meet future global Ag demands and prevent contamination of the environment, all the Ag from end-of-life modules must be recovered instead of landfilled. The most mature Ag recycling recipes use high concentration nitric acid (HNO3) solutions often in combination with heating and agitation. After the Ag is leached, chemical precipitation or electrochemistry is used to recover metallic Ag. However, the process of Ag leaching in the HNO3 system with competing elements from silicon solar cells is not well understood. In this paper, we investigate the thermodynamics governing Ag leaching in low-concentration HNO3 without agitation or heating to expand fundamental knowledge in support of Ag recovery efforts from end-of-life solar panels. ICP-OES is used to quantify the amount of Ag leached in the HNO3 solution over time. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) are used to study the changes on the silicon solar cell surface. Our results suggest when trace tin (Sn) is used in solar cell fingers, it causes Ag to cement in dendritic form.

High-density nanodot structures on silicon solar cell surfaces irradiated by ultraviolet laser pulses below the melting threshold fluence

The surface morphology of silicon solar cells irradiated with KrF excimer laser pulses (λ = 248 nm, τ = 20 ns) was investigated below the experimentally observed melting threshold fluence (F th) of 0.47 J cm−2 (±20%). At laser fluences of 0.23–0.48 J cm−2 (equivalent to 0.49F th to 1.0F th), nanodot structures with a height and width of approximately 60–120 nm were periodically formed with an interdot spacing similar to the laser wavelength. The observed nanodot density (29 dots μm2) was higher than that previously obtained at longer wavelengths. Furthermore, crystallinity analysis by micro-Raman spectroscopy revealed a Raman shift of 519.56 cm−1 after irradiation (N= 1500 pulses), compared with 518.27 cm−1 prior to irradiation. A laser fluence of 0.41 J cm−2 ( = 0.87F th) was found to induce compressive stress on the silicon solar cell surface.

The effect of Te-based lead-free glass powder containing Ge and Ag+ on the contact formation and electrical performance of silicon solar cells

The Te-based glass powder exhibits distinctive characteristics such as a low melting temperature and high chemical stability, rendering it a focal point of research in the realm of glass powder applications for solar cells. In this investigation, a pioneering Ge-containing Te-based lead-free glass powder was synthesized, and the influence of GeO2 content on critical parameters such as glass transition temperature (Tg), high-temperature fluidity, high-temperature wettability, acid and alkali resistance, as well as the network structure of the glass, was systematically explored. At an optimal GeO2 content of 8%, the glass powder displayed the lowest Tg (437°C), accompanied by a subdued crystallization reaction. The high-temperature fluidity and wettability exhibited favorable characteristics, indicating that the inclusion of GeO2 in the glass powder resulted in an enhanced interface contact. Building upon this foundation, techniques to augment the Ag+ content within the glass powder were investigated, along with the interaction between Ag+ and the SiNx anti-reflection layer or silicon on the surface of crystalline silicon solar cells. It was discerned that the Ag+ content in the glass powder significantly influences the deposition of silver microcrystals on the surface of crystalline silicon, thereby impacting the contact resistance of the solar cell. Then influences the series resistance and photoelectric conversion efficiency of the solar cell.

Anisotropic etching behavior and topography formation mechanism of silicon solar cell surface textured by atmospheric plasma

Atmospheric plasma etching (APE) has been used to texture Si surfaces due to anisotropic material removal capability. Controlling features and size of the light-trapping structure are keys to improving the reflection performance of silicon (Si) solar cells, which need to fully understand the interfacial etching behavior and the microscopic topography formation mechanism of the Si surface. In this study, microwave plasma with a temperature below 100 °C is employed to investigate the dependence of microstructure evolution on the O/F atom ratios in plasma. The results show that as the O/F atom ratios increase, the microstructure of the Si surface changes from square opening pits to spherical opening pits. High-resolution transmission electron microscopy and x-ray photoelectron spectroscopy analyses indicate that the exciting F atoms dominate the orientation-selective etching process, causing the formation of square opening pits. The CFx and C2 radicals induce the generation of the Si interface reactive layer, resulting in the occurrence of amorphous layers and termination of the non ⟨111⟩-crystal face in APE. The exciting O atoms preferentially occupy the active site of Si surfaces, causing the isotropic etching and then the formation of spherical opening pits. In addition, the richer O atoms will weaken the anisotropic etching ability of F atoms, resulting in the etched surface trends’ flattening. The insight into anisotropic etching behavior and topography formation mechanism of the silicon surface textured by atmospheric plasma is valuable for developing a new texturing approach to silicon solar cells.

Effective index model as a reliable tool for the design of nanostructured thin-film solar cells

Nanostructured anti-reflection coatings (ARC) are used to reduce the reflectivity of the front surface of solar cells. Computational electromagnetism helps to evaluate the spectral reflectivity of of this type of ARC using several approaches. They typically require large computational resources both in time and hardware elements (memory allocation, speed of processors, etc.). Long computational times may jeopardize optimization processes based on the iterative evaluation of a given merit function that depends on several parameters. Then, simplified analytic methods can speed up this evaluation with moderate computational resources. In this contribution we adapt an Effective Index Model (EIM) to the case of the design of an ARC made with nanoparticles (NP) embedded in a medium at the front surface of a thin-film silicon solar cell. Our approach modifies the discrete dipole approximation method to adapt it to the geometric and material properties of the NPs. The results obtained from the analytic method are compared with those evaluated through a Finite Element Method (FEM) for several cases involving variations in the size and geometry of the NP arrangement, obtaining reflectances that differ less than 10% for the worst case analyzed but bieng about 100 times faster than the FEM.

Biomass-based carbon quantum dots for polycrystalline silicon solar cells with enhanced photovoltaic performance

Polycrystalline silicon solar cells modified using biomass resources are promising candidates to accomplish the goal of carbon neutrality. Developing a device with high power conversion efficiency (PCE) is important to resolve the ever-increasing energy shortage issues. Therefore, we develop a facile solution-casting approach to synthesise ethylene-vinyl acetate (EVA) films modified with ultra-high fluorescent carbon quantum dots (CQDs). The films were coated on the surface of polycrystalline silicon solar cells and the PCE increased from 13.19% to 13.65%. The ultra-high fluorescent CQDs were prepared from Ginkgo biloba via a hydrothermal process, and different parts of Ginkgo biloba-based CQDs were investigated in various conditions. The ultra-high fluorescent CQDs obtained at 180 °C, 8 h and a reaction concentration of 0.048 g/mL from Ginkgo wood resulted in high fluorescence of up to 976.74 a.u.. At an excitation wavelength of 365 nm. This work substantially expands the potential of EVA films containing ultra-high fluorescent CQDs for applications in the photovoltaic, environment and energy fields.

One-step synthesis of aqueous CdTe/CdSe composite QDs toward efficiency enhancement of solar cell

Aqueous quantum dots (QDs) have been widely used in photovoltaic devices. However, aqueous QDs usually perform poorly in terms of optical properties and stability. In this paper, CdTe/CdSe composite QDs were synthesized in an aqueous solution by a simple one-step method, obtaining the tunable optical properties with a photoluminescence quantum yield (PLQY) over 80%. The simultaneous addition of Te and Se sources passivates the defects of CdTe while suppressing the overgrowth of CdSe shell, obtaining core–shell structure with small size and high PLQY. The PVA/QDs film was prepared by spin-coating to achieve up to 26.83% efficiency improvement on the surface of crystalline silicon solar cells, due to the excellent antireflection and down-shifting effect.

A Deep-Red Emission Phosphor Y2SrAl4SiO12:Ce3+, Cr3+ and Its Utilization in Polycrystalline Silicon Solar Cells

The power conversion efficiency (PCE) of crystalline silicon solar cells has reached a bottleneck. Further improving the PCE is an important current research topic. This Letter reports a new phosphor Y2SrAl4SiO12:Ce3+, Cr3+. Under the excitation in the wavelength range of 320-650 nm, the phosphor Y2SrAl4SiO12:Ce3+, Cr3+ exhibits a deep-red emission in the 500-800 nm range. Due to the energy transfer from Ce3+ to Cr3+, the luminescence intensity of Cr3+ is further enhanced. This matches well with the spectrum of silicon solar cells. Because of the powerful absorption and high internal quantum efficiency, Y2SrAl4SiO12:Ce3+, Cr3+ was used to prepare energy down-conversion (EDC) films. By applying the EDC film on the surface of silicon solar cells, the relative PCE increases by 2.018%. These results indicate that Y2SrAl4SiO12:Ce3+, Cr3+ is an excellent deep-red garnet structured phosphor and furthermore has a positive effect on the enhancement of the PCE of solar cells.

Temperature and illumination dependence of silicon heterojunction solar cells with a wide range of wafer resistivities

AbstractRecently, the significant improvements in the surface and contact passivation of silicon (Si) solar cells as well as their bulk quality have shifted their operating point to higher injections. Hence, they are less dependent on wafer doping. This shift opens an opportunity of using high‐resistivity wafers for practical photovoltaic applications, introducing a promising approach to push the cell efficiency towards the intrinsic limit and to improve the module reliability by increasing the cell breakdown voltage. Therefore, insights into the performance of Si solar cells using high‐resistivity wafers at various operating temperatures are of significant interest. In this study, we investigate the temperature‐ and illumination‐dependent performance of Si heterojunction (SHJ) solar cells using a wide range of wafer resistivities (between 3 and 1000 Ω⋅cm). Although a reduction in the passivation quality of the passivating contacts is observed at elevated temperature, the impact on the temperature coefficient of the open‐circuit voltage (TCVoc)—the dominant contributor to the temperature coefficient (TC) of the cell efficiency—is very limited. Their TCVoc are still dominated by the temperature dependence of the effective intrinsic carrier concentration. Furthermore, we also find that the investigated cells are more sensitive to temperature variation at lower illumination intensities. It is noteworthy that the efficiency of the cells fabricated using high‐resistivity wafers is comparable to that of the reference cells at any given temperature, highlighting the potential of using high‐resistivity wafers for solar cells.

Photoresist Microlens Arrays Fabricated by Nanoimprint Technique to Improve the Photoelectric Conversion Efficiency of Solar Cells

Silicon solar cells have the advantages of non-toxicity, reliability, low price, and stability. Microlens arrays (MLAs) are widely used in solar cells to improve photoelectrical conversion efficiency (PCE). In this research, different MLAs mold was designed by a method of thermal reflow. Then the photoresist film MLAs structure was replicated on the surface of silicon solar cells through UV nanoimprint technology. The optical transmission and surface morphology of these photoresist films were respectively measured by using a UV spectrometer and an atomic force microscope. The surface morphology and imaging capabilities of photoresist film MLAs were respectively measured by using a scanning electron microscope and optical microscope. Finally, the photovoltaic performance of the silicon solar cell with the photoresist film MLAs was investigated, and the PCE value of the silicon solar cell improved from 11.53% for the sample without MLAs to 13.19% for the sample with the square MLAs and the PCE improvement is about 14.40%. All these results above show that the photoresist film MLAs can significantly improve the efficiency of silicon solar cells and have great application potential in the field of solar cells.

Design and optimization of single, double and multilayer anti-reflection coatings on planar and textured surface of silicon solar cells

The present silicon solar cell industry's main concern is to increase efficiency by minimizing the surface reflection. As a result, lately, much attention has been paid to the composition and number of the layers used for anti-reflection coatings in order to reduce surface reflection. In the present work, single, double, triple, and quadruple anti-reflection coatings on silicon solar cells have been designed and optimized using FDTD and PC1D simulation methods. The different combinations of SiO2, SiON, Si3N4, and SiNx coatings on both planar and textured surfaces were simulated and their optical and electrical parameters were investigated. Compared to planar surfaces, the designed coatings on textured surfaces showed better optical and electrical results for almost all investigated parameters. On textured surfaces, SiO2/Si3N4/SiNx acquired the lowest weighted average reflection (0.121%), SiO2/SiNx, SiON/SiNx, SiO2/Si3N4/SiNx, and SiO2/SiON/Si3N4/SiNx the highest Jsc(38.5 mA/cm2) and finally SiO2/Si3N4/SiNx and SiO2/SiON/Si3N4/SiNx both the highest Voc(705.7 mV) and η(23%).

Дизайн и анализ просветляющего покрытия на поверхности кристаллического кремния солнечного элемента

With the positive development of photovoltaic technology, improving efficiency and reducing cost has become a global problem facing the solar industry. The development of solar cell anti-reflection film can significantly reduce the reflection of sunlight on the surface of the battery, increase the flux of light entering the battery, and create more photo-generated carriers, which is the most economical and effective way to improve the efficiency of the battery. More photo-generated carriers are produced, which is the most economical and effective way to improve the efficiency of batteries. Therefore, it’s of great value to explore a performance-matched antireflective film material for solar cells and its preparation process. The plasma enhanced chemical vapor deposition of silicon nitride antireflective coatings has been widely used in photovoltaic industry. The aim is to form an antireflection film on the surface of crystalline silicon solar cells and achieve good passivation effect. The thickness and refractive index of the antireflective film have an important influence on the performance of the battery. It is of great significance to explore the optimum technological conditions for preparing the optimum thin films. Considering the optical properties, stability, preparation process and production cost of antireflective film materials, the influence of antireflective film on the output characteristics of solar cells was studied by using PC1D simulation software.

Characterization of Luminescent Down-Shifting Spectral Conversion Effects on Silicon Solar Cells with Various Combinations of Eu-Doped Phosphors.

Luminescent down-shifting (LDS) spectral conversion is a feasible approach to enhancing the short-wavelength response of single junction solar cells. This paper presents the optical and electrical characteristics of LDS spectral conversion layers containing a single species or two species of Eu-doped phosphors applied to the front surface of silicon solar cells via spin-on coating. The chemical composition, surface morphology, and fluorescence emission of the LDS layers were respectively characterized using energy-dispersive X-ray analysis, optical imaging, and photoluminescence measurements. We also examined the LDS effects of various phosphors on silicon solar cells in terms of optical reflectance and external quantum efficiency. Finally, we examined the LDS effects of the phosphors on photovoltaic performance by measuring photovoltaic current density–voltage characteristics using an air-mass 1.5 global solar simulator. Compared to the control cell, the application of a single phosphor enhanced efficiency by 17.39% (from 11.14% to 13.07%), whereas the application of two different phosphors enhanced efficiency by 31.63% (from 11.14% to 14.66%).

EVALUATING THE EFFICIENCY OF ANTI-REFLECTIVE SURFACES OF SILICON SOLAR CELLS PART 1. OPTICAL CHARACTERISTICS

Optical characteristics of anti-reflective surfaces of silicon solar cells with various types of irregularities (microstructured pyramid, nanostructured hole, column and cone) are modeled by the finite-difference time-domain method and experimentally studied. It is shown that surfaces with conical irregularities, which are formed by the method of reactive ion etching in the black silicon formation mode, are the most effective. The expediency of hybrid application of micro- and nanostructured antireflection surfaces in industrial solar cells is discussed.

Micro/Nanostructures for Light Trapping in Monocrystalline Silicon Solar Cells

Due to the ongoing depletion of fossil energy, alternative energy‐sources and their respective conversion technologies have become very essential. An inexhaustible and clean energy form, which is already widely used, is solar energy. However, despite much progress in recent decades, due to the limitations of materials and manufacturing technology, the ability of solar cells to convert light into electrical energy is still not very high. Enhancing light absorption and reducing electric loss are the keys to improving the overall conversion efficiency of solar cells and reducing raw material costs. The former can be achieved by using micro/nanostructures and other surface features, while the latter can be realized by surface passivation. Researchers have developed different silicon‐surface texturing methods to fabricate random or periodic micro/nanostructures on the surface of silicon wafers. Thanks to the special and efficient light‐trapping effects of silicon micro/nanostructures, both full angle and wideband light absorption can be achieved. Different passivation methods and materials have also been widely studied, which helps to improve the surface recombination of photogenerated carriers caused by light trapping structure and significantly enhance the power conversion efficiency of Si solar cells. In this work, theoretical studies of enhanced light‐trapping in micro/nanostructures are introduced. In addition, several advanced methods for preparing micro/nanostructures on the surface of monocrystalline silicon are discussed. These can be classified as top‐down and bottom‐up approaches. Furthermore, passivation methods for micro/nanostructures on the surface of monocrystalline silicon solar cells are reviewed, including chemical passivation and field‐effect passivation. Finally, advantages and disadvantages of the micro/nanostructure preparation technologies, and light‐trapping effects of the micro/nanostructures, which were fabricated using these manufacturing technologies were summarized. Moreover, the effects of different passivation technologies on the optical properties and electrical properties of these micro/nanostructures are studied. An outlook of expected and emerging research directions for monocrystalline silicon solar cells concludes this study.

Formation of inverted pyramid-like structures on surfaces of single crystalline silicon solar cells by chemical wet etching

We present a new, simple, and cost-effective etching method for forming inverted pyramid-like structures on the surfaces of single-crystalline diamond-wire sawn silicon wafers. The method follows a three-step process for etching silicon wafers without metal-assisted chemical etching involved. We used acidic etching to produce nano-to-micro-structured caves in the first two steps followed by anisotropic etching with an alkaline solution. This paper shows that the size of the opening of the inverted pyramid could vary from several hundred nanometers to about 4 μm, depending on the etch time periods in the second and the third steps. The cell performance was, however, only evaluated here for cases of smaller sizes of inverted pyramids. That is, solar cells were manufactured following an almost commercially standard procedure by using wafers with inverted pyramids of ∼900 nm in size. The best cell with this type of structure has a conversion efficiency of 19.22%, which is higher relative to the cells with smaller inward recessed caves or upright pyramids on the surfaces.

The Effect of Laser Heating and Overcasting Deposition on the Efficiency of Plasmonic Solar Cell with Noble Metallic Nanostructures

Surface plasmon resonance could increase the efficiency of solar cells , when light is trapped by the noble metallic nanoparticles arrangement at and into the silicon solar cell (SSC) surface. Pure noble metal (silver and gold) nanoparticles (NPs) have been synthesized as colloids in de-ionized water (DW) by pulsed laser ablation (PLA) process at optimum laser fluence. Silicon solar cell with low efficiency was converted to plasmonic silicon solar cell by overcasting deposition method of silver nanoparticles on the front side of the SSC. The performance of plasmonic solar cell (PSC) was increased due to light trapping. Two mechanisms were involved : inserting silver nanoparticles (Ag NPs) inside the silicon layer by the heating effect of pulsed laser and depositing gold nanoparticles (Au NPs) on the surface of the SSC by overcasting method. The optical properties of silver and gold colloidal solutions were studied with UV- Visible spectrophotometer with a range from 190 nm to 1100 nm. The absorption spectra showed single absorption peak located at about the characteristic value for silver and gold nanoparticles due to the surface plasmon resonance. Atomic Force Microscope (AFM) images were studied , the ablated noble NPs by pulsed laser have an average diameter less than 100 nm. AFM images showed the morphology of SSC surface without and with nanoparticles before and after overcasting and heating by laser methods. Electrical measurements for SSC namely current – voltage ( I-V )characteristics and responsivity (Rλ) displayed higher efficiency after these procedures. The efficiency rise to(5.2%) due to the localized surface plasmons excitation of (Ag NPs) that were embedded into the silicon layer by the heating effect of pulsed laser. The deposition of AuNPs on the silicon surface of the plasmonic SC additionally increased the efficiency to (7.28%), due to light trapping by scattering from Au NPs towards the plasmonic solar cell depth .

Structural and optical study of amorphous hydrogenated silicon nitride thin film as antireflection coating on solar cell

The structural, optical and electrical aspects of as deposited as well as annealed amorphous hydrogenated silicon nitride(a-SiNx: H) thin films of different stoichiometry, grown on silicon wafer by radio frequency- plasma enhanced chemical vapor deposition (RF-PECVD) are thoroughly investigated. Photoluminescence (PL) measurement verify that Si rich a-SiNx: H (SRSN) film of refractive index 2.68, gives good PL as compared to near stoichiometric film and support the presence of Silicon quantum dots (Si QDs) embedded in a-SiNx: H matrix. Detailed structural analysis by high resolution transmission electron microscopy (HRTEM) revealed that as deposited SRSN thin film contains amorphous Silicon quantum dots (a-Si QDs) which are grown by phase separation of SRSN film during the synthesis process. These SRSN thin films of different thicknesses have been deposited at the surface of Silicon solar cell as anti-reflection coatings (ARCs). By reflectance measurement, it is observed that the ARC contains a-Si QDs in a-SiNx: H matrix, more effectively minimize the reflection of incident light across the wavelengths ranging from 300 to 800 nm. With a-Si QDs/ a-SiNx: H ARC, we demonstrate an increase in short circuit current density, open circuit voltage and conversion efficiency by 4.34 mA/cm2, 0.01V and 0.21% (absolute) respectively and indicate its utility in improving the performance of Si solar cells. Copyright © 2017 VBRI Press.

Studying the effect of light intensity and the dust on efficiency of Silicon Solar cell

In this paper, Two main effected parameters on the efficiency of solar cell has studied: the increasing in the amount of intensity of incident solar irradiance on the surface of silicon solar cell and accumulation of dust on the front face of solar cell. The parameters of silicon solar cell (Isc, Voc, pmax, η) have been studied under various quantities of solar irradiations (G= 100, 172,252 and 606W/m2 ) at a constant temperature (TC=25±2) ͦ C. The results showed an increasing in the value of conversion efficiency( fromη=7.1% to η=10%) with the increasing of intensity of solar flux. But the dust had a reverse effect on the value of conversion efficiency , thus after one week there was noticeable of(∆Isc= 5%) degradation at value of short circuit that lead to decrease of conversion efficiency.

Measurement and Analysis of Optical Properties of Polymer Films with Triangular Pyramid Optical Functional Texture

A poly (vinyl chloride) film with triangular pyramid array structure was designed and fabricated. In this paper, a plane to plane hot embossing technique is used to fabricate a triangular pyramid antireflection film on the surface of single crystal silicon solar cells. By testing the optical properties of optical functional textured films, it is found that the reflectivity of triangular pyramid textured films obtained by hot embossing is significantly lower than that of smooth flat films; The absorption and antireflection of high light on the film surface are obvious; The photoelectric conversion efficiency of the solar cell is further improved. Triangular pyramid optical functional structure has great potential in improving the performance of silicon solar cells, which can be applied to different types of solar cells. These improvements are of great significance to the commercialization of silicon solar cell devices.