Crystalline Silicon Research Articles

Life cycle assessment of recycling waste crystalline silicon photovoltaic modules: A comparison between traditional and green solvent recycling processes

Crystalline silicon photovoltaic (PV) modules that have reached the end of their service life, if not effectively recycled, result in the loss of valuable resources such as silicon, silver, aluminum, and others. Moreover, improper disposal can lead to long-term environmental pollution. Therefore, the development of efficient and green recycling technologies for waste PV modules has become a key focus of current research. In this study, a life cycle assessment (LCA) of green solvent recycling (GSR) and traditional recycling technologies was conducted using the ReCiPe 2016 Mid-point evaluation method. The energy and resources consumed, along with the environmental impacts generated, were comparatively analysed, and their resource recovery benefits were calculated. Results show that GSR performs well in terms of environmental impact and even better in terms of resource recovery benefits. Leaching with 1,3-dimethyl-2-imidazolidinone (DMI) solvents reduces global warming potential by 487 kg CO2 eq compared to nitric acid used in chemical recycling. Deep eutectic solvents (DES) achieve higher leaching rates of up to 99 %, compared to metals recovered via mechanical separation, and reduce terrestrial ecotoxicity by 742 kg of 1,4-DCB. Of all energy and resource inputs, electricity consumption contributes the most to environmental impacts. In summary, this study offers a more environmentally friendly and effective recycling solution for the PV industry, supporting its green transformation and sustainable development.

A Pyrrole Modified 3,4-Propylenedioxythiophene Conjugated Polymer as Hole Transport Layer for Efficient and Stable Perovskite Solar Cells.

Despite the outstanding electric properties and cost-effectiveness of poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives, their performance as hole transport layer (HTL) materials in conventional perovskite solar cells (PSCs) has lagged behind that of widely used spirobifluorene-based molecules or poly(triaryl amine). This gap is mainly from their poor solubility and energy alignment mismatch. In this work, the design and synthesis of a pyrrole-modified HTL (PPr) based on 3,4-propylenedioxythiophene (ProDOT) are presented for efficient and stable PSCs. As a result of the superior defects passivation ability, excellent contact with perovskite, enhanced hole extraction, and high hydrophobicity, the unencapsulated PPr-based PSCs showed the peak PCE of 21.49% and outstanding moisture stability (over 4000 h). This work highlights the potential application of ProDOT-based materials as HTL for PSCs and underscores the importance of the rational design of PEDOT and its derivatives.

Reusable SERS Platform of Femtosecond Laser Processed Substrate for Detection of Malachite Green.

This study presents the development of highly efficient Surface-Enhanced Raman Scattering (SERS) substrates through femtosecond (fs) laser processing of crystalline silicon (Si), resulting in mountain-like microstructures. These microstructures, when decorated with gold nanoparticles (Au NPs), exhibit remarkable SERS performance due to the creation of concentrated hotspots. The enhanced Raman signals originate from the excitation of localized surface plasmon resonance (LSPR) of the Au NPs and the multi-scale rough morphology of the Si substrates. Finite-element method simulations confirm the electromagnetic field enhancement in narrow gaps, supporting the experimental observations. The fabricated substrates show high uniformity, oxidation resistance, long-term stability, and exceptional reproducibility, making them ideal for molecular detection, especially in food safety applications. A remarkable enhancement factor (EF) of 1010 is attained in the detection of Malachite Green (MG), boasting a limit of detection (LoD) as low as 10-14 M. This underscores the immense potential of this technique for achieving highly sensitive and dependable SERS-based sensing capabilities.

Simple Smoothing of the Bottom Silicon Surface Using Wet Chemical Etching Methods for Epitaxial III‐V/Silicon Tandem Manufacturing

The implementation of diverse technologies has recently facilitated the production of cost‐effective and highly efficient solar cells. High‐efficiency solar cells with III‐V compounds tandem crystalline silicon cells have achieved photovoltaic efficiency of higher than 39%. Etching silicon wafers plays a vital role in the deposition of epitaxial layers, neutralizing dangling bonds, and surface passivation for tandem solar cells. The wafers are polished using a solution of HF–HNO3–CH3COOH (HNA) and 20% KOH to smoothen the wafer surface. When HNA wet etching is performed for 3.5 min and the 20% KOH etching lasts for 6 min, the microroughness of the wafer is 1.9 nm with a measurement area of 10 × 10 μm2 and 0.816 nm within an area of 1 × 1 μm2. Compared with the as‐cut wafer, the reflectance increases from 31.7% to 34.7%, and the effective minority carrier lifetime, with 30 nm Al2O3 passivation after 450 °C activated, increases from 1.4 to 1.8 ms in a carrier density of 1.0 × 1015 cm−3.

Degradation of crystalline silicon solar cells caused by lightning induced impulse surge

Abstract Crystalline silicon (c-Si) solar cells are connected in series to form photovoltaic modules, which are installed in wide-open areas. They are exposed to lightning electromagnetic (EM) interference at high risk. The lightning EM field can induce an impulse surge in the loop of the solar-cell string, and c-Si solar cells are prone to damage. To study the effect of lightning surge on monocrystalline silicon cells and polycrystalline silicon cells, impulse voltage tests are conducted. Semiconductor structures of c-Si solar cells after testing are observed using scanning electron microscopy. The results indicate that the lightning surge will generate some cracks and defects in the P–N junction. Under a strong electric field, the N-type emitter layer and the grain boundary can be destroyed, which contributes to the degradation of the c-Si solar cell. Compared to monocrystalline silicon cells, polycrystalline silicon cells can withstand greater forward lightning surge; however, their maximum reverse lightning surge is relatively low.

Rising Tide of Enhanced Crystalline Silicon Luminescence via Optical Resonance.

Since the invention of lasers, research on the luminescence of crystalline silicon (c-Si) has been a longstanding challenge in the field of photonics. Recent advancements in nanofabrication technology, coupled with in-depth investigations into optical resonance and carrier dynamics, have enabled the realization of efficient luminescence in c-Si.

Investigating the Impact of Hydrogen Bonding on Silicon Nitride (SiNx) Film

The deposition of amorphous hydrogenated silicon nitride (a‐SiNx:H) via plasma‐enhanced chemical vapor deposition is critical for optimizing the performance of crystalline silicon (c‐Si) solar cells. This study investigates the impact of varying gas ratios (GR = NH3/SiH4) on the optical and physical properties of deposited SiNx films. Results show that the refractive index (RI) ranges from 1.8 to 2.3 with changing gas compositions. Fourier transform infrared Spectroscopy reveals shifts in [SiNH] and [SiH] stretching modes, indicating changes in hydrogen passivation and nitrogen incorporation. Hydrogen bonding densities of [SiH] and [SiNH] correlate positively with the RI. For example, the hydrogen bonding density [NH] ranges from 4.53 × 1023 to 6.32 × 1023 cm−3 for [SiNH] bonds while [Si‐H] varies from 6.93 × 1023 to 1.06 × 1024 cm−3. Secondary ion mass spectrometry (SIMS) analysis shows stable hydrogen intensity, contrasting with a decrease in nitrogenhydrogen bonds. These findings highlight the key role of hydrogen bonding in determining SiNx film properties, with significant implications for semiconductor and photovoltaic applications.

Ultrathin Self-Assembled Monolayer for Effective Silicon Solar Cell Passivation.

Passivation technology is crucial for reducing interface defects and impacting the performance of crystalline silicon (c-Si) solar cells. Concurrently, maintaining a thin passivation layer is essential for ensuring efficient carrier transport. With an ultrathin passivated contact structure, both Silicon Heterojunction (SHJ) cells and Tunnel Oxide Passivated Contact (TOPCon) solar cells achieve an efficiency surpassing 26%. To reduce production costs and simplify solar cell manufacturing processes, the rapid development of organic material passivation technology has emerged. However, its widespread industrial production is hindered by environmental safety concerns, such as strong acid corrosion and biological and ecological safety issues. Here, we discovered a low-cost self-assembled monolayer (SAM) hole-selective transport material known as 2PACz ([2-(9H-carbazol-9-yl) ethyl] phosphonic acid) with phosphate groups to form c-Si solar cells for the first time. The ultrathin film of 2PACz with phosphate groups can establish strong and stable P-O-Si bonds on the silicon surface. Meanwhile, like 2PACz, a uniform ultrathin film with a carbazole function group can offer electron-localizing and thus hole-selective properties, which provides ideas for studying dopant-free silicon solar cells. As a result of such interfacial passivation engineering, it plays an important role in repairing porous structures, such as pyramid-textured silicon surfaces, and cutting losses during the commercialization of c-Si solar cells. Crucially, this advancement offers insights for the development of new high-efficiency ultrathin film passivation methods in the postsilicon era.

Efficient and swift heating technique for crafting highly graphitized carbon and crystalline silicon (Si@GC) composite anodes for lithium‐ion batteries

Efficient and swift heating technique for crafting highly graphitized carbon and crystalline silicon (Si@GC) composite anodes for lithium‐ion batteries

Structural, electronic, and optical-absorption properties of 2D Si thin films

AbstractRecent experimental studies highlighted the potential of thin-film crystalline silicon (Si) for high-efficiency solar cells. Using density functional theory, we investigated 2D Si thin films across various orientations, thicknesses, and surface structures to elucidate their structure–property relationships. Through surface-energy calculations and Wulff construction, we determined the crystal habit of Si, which aligns with available experimental observations. Electronic-structure calculations underscored the critical role of valence saturation on surfaces in enabling semiconducting behavior in Si thin films, essential for optical applications. From optical-absorption calculations, we identified the surface index exhibiting the highest absorption coefficients for thin films Si solar cell applications. Graphical abstract

Tailoring Perovskite/C60 Interface by Reactive Passivators for Stable Tandem Solar Cells

AbstractIntegrating perovskite solar cells with crystalline silicon bottom cells in a monolithic two‐terminal tandem configuration enables power conversion efficiency (PCE) surpassing the theoretical limits of single‐junction cells. However, wide bandgap (WBG) perovskite films face challenges related to phase stability and open circuit voltage (VOC) deficit, particularly due to severe non‐radiative recombination at the perovskite/C60 interface. Here, the interfacial defects are passivated by incorporating a reactive passivator that reacts with lead halides to form low‐dimensional phases. The target product obtained by optimizing the reaction temperature not only suppresses recombination across the interface, but also facilitates the transfer of charge carriers. More importantly, this product can suppress phase segregation of WBG perovskite films under exposure to light illumination and moisture. This strategy enables a high VOC of 1.25 V for WBG perovskite device based on polymer hole transport layer and a certified stabilized PCE of 30.52% for a monolithic perovskite/silicon tandem solar cell. The unencapsulated tandem device retains 94% of its initial PCE over 200 h under continuous 1‐sun full spectrum illumination in air, demonstrating the improved phase stability.

Enhancing perovskite solar cells performance through tailored design: pyridine-functionalized phenothiazine derivatives with modified end-capped acceptor moieties

Abstract Future energy resources are being developed using clean and renewable energies since these sources offer environmentally friendly and sustainable choices to traditional sources like fossil fuels. Among various renewable energy sources, solar energy is becoming increasingly efficient with advancements in organic photovoltaic systems. Organic semiconductor materials, which require high electron affinity and possess desirable optical and electronic properties, are crucial for these systems. Researchers are constantly trying to increase the role of photovoltaic materials in optoelectronic applications. With current energy demands, there is a shift from traditional solar cells to perovskite photovoltaic materials due to their significant contributions to renewable energy. Therefore, we have designed a new stream of donor- π -acceptor (D- π -A) type pyridine functionalized phenothiazine derivates-based donor materials, resulting in nine fabricated HTMs (PT1-PT9), by substituting the terminals with thiophene and acceptors moieties respectively to enhance the photovoltaic properties of perovskite solar cells (PSCs). All newly proposed materials were computationally examined to estimate their optoelectronics, geometrical, and photovoltaic properties using quantum chemical approach, and then compared to the reference. For organic hole-transporting materials, a heterocyclic phenothiazine core (PTZ) has been proven effective as it has feasible structure modifications, excellent electron-donating properties, and straightforward synthesis. The study of electronic parameters (density of state, frontier molecular orbitals, and electrostatic potential ESP), optical properties (light harvesting efficiency, absorption maxima, dipole moment, and first excitation energies) and charge transfer characteristics (electron–hole overlap, transition density matrix) of designed materials revealed that there is an increase in absorption range under the influence of terminal acceptor groups, with lowering the bandgap values compared to the reference. A density of state (DOS) graph and HOMO–LUMO schema are evidence of the electron-withdrawing effect of acceptor moieties. Transition density matrix (TDM) analysis proves reliable charger transfer in designed molecules. Reorganization energy values for designed molecules are lower than the reference making charge transfer carriers more efficient. Additionally, solvation-free energy values (−17.28 to −33.19 Kcalmol−1) and higher dipole moments suggest better surface-wetting and solubility properties. In general, the fabricated materials have exceptional charge mobilities with higher absorption and reduced band gap values that make them suitable and stable candidates for photovoltaic devices.

Highly effective passivation of crystalline silicon surfaces achieved through transparent conductive Al-doped ZnO layers

Highly effective passivation of crystalline silicon surfaces achieved through transparent conductive Al-doped ZnO layers

Electronic Passivation of Crystalline Silicon Surfaces Using Spatial‐Atomic‐Layer‐Deposited HfO2 Films and HfO2/SiNx Stacks

Spatial atomic layer deposition (SALD) is applied to the electronic passivation of moderately doped (≈1016 cm−3) p‐type crystalline silicon surfaces by thin layers of hafnium oxide (HfO2). For 10 nm thick HfO2 layers annealed at 400 °C, an effective surface recombination velocity Seff of 4 cm s−1 is achieved, which is below what has been reported before on moderately doped p‐type silicon. The one‐sun implied open‐circuit voltage amounts to iVoc = 727 mV. After firing at 700 °C peak temperature in a conveyor‐belt furnace, as applied in the production of solar cells, still a good level of surface passivation with an Seff of 21 cm s−1 is attained. Reducing the HfO2 thickness to 1 nm, the passivation virtually vanishes after firing (i.e., Seff > 1000 cm s−1). However, by adding a capping layer of plasma‐enhanced‐chemical‐vapor‐deposited hydrogen‐rich silicon nitride (SiNx) onto the 1 nm HfO2, a substantially improved firing stability is attained, as demonstrated by Seff values as low as 30 cm s−1 after firing, which is attributed to the hydrogenation of interface states. The presented study demonstrates that SALD‐deposited HfO2 layers and HfO2/SiNx stacks have the potential to evolve into an attractive surface passivation scheme for future solar cells.

The preliminary study of etching characteristics of atmospheric pressure trifluoromethane plasma jet etching

Abstract The capacitive coupling radio frequency atmospheric pressure plasma jet for silicon etching, through the carrier gas carrying trifluoromethane gas, varying the gas flow rate for plasma etching. It finds the impact of varying gas flow rates on plasma etching and analyzes the resulting two-dimensional and three-dimensional surface topographies using surface profilometer. Experimental findings indicate that at a trifluoromethane flow rate of 250 sccm and a working distance of 6 mm, the etching rate achieves 38.7 μm/min. Notably, the research emphasizes the crucial role of trifluoromethane (CHF3) gas in plasma etching, highlighting its fluorocarbon ratio and chemical structure as primary factors influencing the etching process on monocrystalline silicon. Ultimately, the study proposes a methodology involving trifluoromethane gas for silicon wafer etching, enabling the transformation of micro-patterns onto crystalline silicon using a mask. This research contributes valuable insights into optimizing plasma etching techniques for microfabrication processes in semiconductor technology.

Density functional theory study of cobalt sulfide as a counter electrode material for dye-sensitized solar cells

Abstract Dye-sensitized solar cells (DSSCs) are viewed as potential substitutes for traditional silicon-based solar cells due to their affordability, impressive performance in low-light conditions, eco-friendly energy production, and adaptability in solar product integration. The use of noble metals such as platinum as counter electrodes in DSSCs was initially limited by their high cost; however, cobalt sulfide has been recognized as a viable alternative due to its abundance, non-toxic properties, and cost-effectiveness. In this work, the crystal structure, electronic, optical characteristics and electrocatalytic activity of the tetragonal phases of cobalt sulfide are investigated through density functional theory with a quantum espresso package. The results obtained for the lattice parameter are a = b = 3.53 Å and c = 4.80 Å. The generalized gradient approximation and hybrid exchange correlation function yield bandgaps of 1.63 and 1.69 eV, respectively, which are consistent with the reported experimental values. An analysis of the density of states and the projected density was carried out to validate the accuracy of the calculated band gaps. Additionally, significant information was obtained from the optical properties through the calculation of the dielectric function. The findings reveal real and imaginary static dielectric constants of 11.85 and 0.13, respectively. Furthermore, the measured absorption and conductivity spectra exhibit promising attributes in the UV–visible range and good electrical conductivity. Moreover, the electrocatalytic activity was studied to analyze the adsorption energy of CoS and the electrolyte. Generally, the calculated electronic and optical properties of CoS crystals indicate their potential application as counter electrodes in dye-sensitized solar cells.

Enhanced Schottky barrier engineering in silver-doped TiO2/p-Si heterojunctions: Insights into electrical behavior and charge carrier dynamics

Heterojunctions were fabricated through the deposition of silver-doped Titanium dioxide (Ag–TiO2) onto p-type crystalline silicon, employing the sol-gel technique. Electrical characterization was conducted with varying Ag concentrations. The investigation revealed that the Schottky barriers at each interface (Ag/TiO2 and Si/Ag), along with the built-in potential at the TiO2/p-Si junction, increase proportionally with the Ag concentration. This observed trend was attributed to the reduction in the TiO2 bandgap due to Ag incorporation, resulting in a concurrent shift in both valence and conduction bands. Consequently, there is a growth of the conduction energy discontinuity and a reduction in the valence one, facilitating hole diffusion while impeding electron transfer across the depletion layer. Furthermore, the introduction of Ag leads to a decrease in both electron and hole concentrations. However, Ag incorporation within the TiO2 matrix manifests as nanoparticles and clusters, resulting in a nonhomogeneous distribution of charge carriers across the sample. Impedance analysis indicates an increase in device resistance and a decrease in effective capacitance.

Ultrathin SiONC passivation of c-Si by UHV thermal annealing in O₂/N₂: Chemical composition, morphology, and photoluminescence insights

This study investigates the impact of Ultra-High Vacuum (UHV) Thermal annealing in a N₂/O₂ atmosphere on the passivation of Ar ion etched crystalline silicon (c-Si) surfaces. A comprehensive analysis of the resulting ultrathin Silicon OxyNitride Carbide layer (SiONC) was conducted using X-ray Photoelectron Spectroscopy (XPS), Ultra-Violet Spectroscopy (UPS), Photoluminescence Spectroscopy (PL), and Atomic Force Microscopy (AFM). XPS revealed a significant transformation in chemical composition from a carbon-rich contaminated surface SiO1.02C2.98 to an oxygen- and nitrogen-containing passivated layer SiO0.13N0.10C0.28. UPS measurements elucidated changes in the electronic structure and Fermi level position at the c-Si/SiONC interface. AFM imaging demonstrated the formation of non-uniform SiONC islands, influencing surface morphology. Notably, PL spectroscopy indicated enhanced orange and red luminescence with energies of 2.0 and 1.73 eV, respectively, attributed to the SiONC layer. The enhanced luminescence, coupled with improved thermal stability and oxidation resistance, positions the SiONC layer as a promising material for advancing the performance of silicon-based optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). This study provides fundamental insights into the correlation between the chemical, electronic, and morphological properties of the SiONC layer and its potential for improving c-Si device performance.

Life cycle assessment of photovoltaic panels including transportation and two end-of-life scenarios: Shaping a sustainable future for renewable energy

This research study addresses the growing environmental concerns associated with solar photovoltaic (PV) systems which is a pivotal component of renewable energy transition. The primary objective is to advance the comprehension of the environmental sustainability of solar PV technology, with a specific focus on the context of Mexico. This study applies a life cycle assessment (LCA) framework, employing an up-to-date methodology (ReCiPe 2016) and database (Ecoinvent 3.8) for midpoint and endpoint indicators in this problem by considering a specific focus on end-of-life and transportation scenarios which have been absent in the current state-of-the-art research. An LCA approach bridges the gap between midpoint and end-point indicators, bringing transparency to the environmental impact assessment. This research entails a cradle-to-grave LCA of a 1 kW crystalline silicon solar panel over a 25-year lifespan while adapting to ISO 14044 standards for LCA and encompassing both midpoint and end-point indicators, specifically including end-of-life and transportation scenario. Furthermore, a sensitivity analysis is conducted to evaluate the variations in environmental indicators considering the life-cycle data. It is reported that recycling processes can cause a substantial mitigating effect on environmental impacts across multiple categories, leading to reductions of up to 89 % in mineral resource scarcity. Notably, the cell processing phase emerges as the most environmentally impactful stage, accounting for 37 % of the total impact. This high impact is predominantly attributed to silver usage and heightened electricity consumption. The sensitivity analysis revealed that various performance indicators exhibited differing degrees of sensitivity to uncertainty in the design variables, highlighting the importance of careful consideration, particularly in addressing theimpact on theecosystem, when aiming to reduce environmental impacts in the life cycle of silicon solar panels. Our results have also indicated that transportation significantly impacts resource protection, accounting for 15 % of the total impacts in this category, with lesser yet notable contributions to ecosystems and human health. The implications of this work suggest a need for stringent policies to fabricate complete solar photovoltaic modules in Mexico to reduce the environmental burden caused by transportation. Additionally, the insights from this study offer a gateway for the Mexican government to reform current energy transition policies by including multiple recycling scenarios for solar photovoltaic systems, ultimately leading to sustainable growth in this market.

Generated power forecast of dye-sensitized solar plant with deep neural network

ABSTRACT The enormous amount of solar power and its state-of-the-art capturing technology that produces electricity, increases the grid interconnection rate of photovoltaic (PV) plants. Prior knowledge of the aperiodic characteristics of solar energy received by the Earth’s surface is essential for PV plants to ensure reliable operation and stable, secure grid connections. Power generation under diffused sunlight by PV plants with the most widely used first-generation solar cells has significant limitations. A dye-sensitized solar plant (DSSP), utilizes dye-sensitized solar cell (DSSC) technology, remains active in low light conditions. Though the activeness enables such plants to generate electricity throughout the year while receiving diffuse sunlight, unlike conventional solar technologies the plants have a requirement of knowledge of future power generation. This could be the first paper to report on the generated power forecast for such plants. The study has utilized a machine learning approach with a proposed DSSP model for the forecast. Spyder, an open-source integrated development environment, is the test workbench for the experimentation. The results show the robustness and reliability of the method, regardless of the weather conditions in the test area. The DSSP, along with the prediction model, will moderately overcome the shortcomings of power generation under diffuse daylight with intermittent solar radiation and grid connections.