Crystalline Silicon Research Articles

Annual degradation rates and soiling losses of photovoltaic systems composed of recent crystalline silicon technologies in temperate climate

AbstractThe purpose of this study is to investigate the annual degradation rates of photovoltaic (PV) systems composed of PV modules based on recent crystalline silicon (c‐Si) PV technologies. We investigated the annual degradation rates of four PV systems composed of different c‐Si PV technologies, comprising p‐type multi‐crystalline silicon with a passivated emitter rear cell, n‐type silicon heterojunction, p‐type single‐crystalline silicon (sc‐Si) with an aluminum back surface field, and n‐type (sc‐Si) solar cell technologies. These systems were located in Gunma Prefecture in Japan and were measured over 6 years. Furthermore, the effects of soiling on the annual degradation rates of these PV systems were examined by partially surface cleaning the PV arrays two times. The results obtained indicate that the apparent annual degradation rates of the PV strings before surface cleaning were 0.8, 1.6, 1.4, and 1.2%/year, respectively, because of optical losses due to dust particles. However, the inherent annual degradation rates of the PV strings after surface cleaning were 0.1, 0.6, 0.0, and 0.3%/year, respectively. These low degradation rates indicate that the PV systems composed of the recent c‐Si PV technologies all offered reasonably stable performance that was reduced by 3.6%, 5.5%, 7.3%, and 4.8%, respectively because of the effects of surface soiling, although the surfaces of the PV arrays had been washed by plentiful rainfall under their humid subtropical climatic operating conditions.

Suppressing The Blistering of Silicon Nitride in PERC Solar Cells for High Industrial Yield

Passivated emitter and rear contact (PERC) solar cells possess the highest photovoltaic market share at present. In industrial production, blistering of the rear silicon nitride (SiNx) passivation layer significantly affects the yield. In order to solve this problem, the relevant processes for manufacturing the PERC solar cells have been carefully studied. It was found that polishing of the silicon wafer rear surface, aluminum (AlOx) thickness, and the deposition process of the SiNx layer will affect the blistering ratio. By optimizing the manufacturing process mentioned above, the blistering ratio of the PERC solar cells has been effectively suppressed. This work not only provides reliable technical support for the yield improvement of the PERC solar cells but also provides some useful reference for the tunnel oxide passivated contact (TOPcon) and back contact (BC) solar cell industrial manufacture.

Analysis of nickel oxide as a counter electrode for dye-sensitized solar cells using OghmaNano software

Dye-sensitized solar cells (DSSCs), a promising green technology, convert solar energy into electricity more cost-effectively than traditional solar cells. While platinum (Pt) is commonly used in DSSCs, its high cost and toxicity limit practical applications. Recent research aims to develop low-cost counter electrodes with high efficiency. Nickel oxide (NiO), a p-type semiconductor with a wide bandgap, good transmittance, and suitable work function, emerges as a potential alternative for counter electrode of DSSCs. In this work, DSSCs with NiO of thicknesses varying from 100 nm to 1000 nm were simulated to determine its influence on photovoltaic performance using OghmaNano software. The structure of simulated solar cells consists of NiO as counter electrode, zinc oxide (ZnO) as photoanode, N719 as dyes, electrolyte as charge carrier transport, and fluorine-doped tin oxide (FTO) as a contact layer. There are five data of NiO used as an active layer. From the simulation results, NiO-doped gold exhibits the highest power conversion efficiency (PCE) of 15.95% at a thickness of 700 nm, while pure NiO shows the lowest PCE with 4.53% at a thickness of 600 nm. These results have demonstrated that NiO can replace Pt as a counter electrode for DSSCs and doping plays a vital role in increasing efficiency.

Scrutinizing transport phenomena and recombination mechanisms in thin film Sb2S3 solar cells

The Schockley–Quisser (SQ) limit of 28.64% is distant from the Sb2S3 solar cells’ record power conversion efficiency (PCE), which is 8.00%. Such poor efficiency is mostly owing to substantial interface-induced recombination losses caused by defects at the interfaces and misaligned energy levels. The endeavor of this study is to investigate an efficient Sb2S3 solar cell structure via accurate analytical modeling. The proposed model considers different recombination mechanisms such as non-radiative recombination, Sb2S3/CdS interface recombination, Auger, SRH, tunneling-enhanced recombination, and their combined impact on solar cell performance. This model is verified against experimental work (Glass/ITO/CdS/Sb2S3/Au) where a good coincidence is achieved. Several parameters effects such as thickness, doping, electronic affinity, and bandgap are scrutinized. The effect of both bulk traps located in CdS and Sb2S3 on the electrical outputs of the solar cell is analyzed thoroughly. Besides, a deep insight into the effect of interfacial traps on solar cell figures of merits is gained through shedding light into their relation with carriers’ minority lifetime, diffusion length, and surface recombination velocity. Our research findings illuminate that the primary contributors to Sb2S3 degradation are interfacial traps and series resistance. Furthermore, achieving optimal band alignment by fine-tuning the electron affinity of CdS to create a Spike-like conformation is crucial for enhancing the immunity of the device versus the interfacial traps. In our study, the optimized solar cell configuration (Glass/ITO/CdS/Sb2S3/Au) demonstrates remarkable performance, including a high short-circuit current (JSC) of 47.9 mA/cm2, an open-circuit voltage (VOC) of 1.16 V, a fill factor (FF) of 54%, and a notable improvement in conversion efficiency by approximately 30% compared to conventional solar cells. Beyond its superior performance, the optimized Sb2S3 solar cell also exhibits enhanced reliability in mitigating interfacial traps at the CdS/Sb2S3 junction. This improved reliability can be attributed to our precise control of band alignment and the fine-tuning of influencing parameters.

Interfacial host-guest complexation for inverted perovskite solar cells.

Perovskite solar cells have demonstrated exceptional development over the past decade, but their stability remains a challenge toward the application of this technology. Several strategies have been used to address this, and the use of host-guest complexation has recently attracted more interest. However, this approach has primarily been exploited in conventional perovskite solar cells based on n-i-p architectures, while its use in inverted p-i-n devices remains unexplored. Herein, we employ representative crown ether, dibenzo-24-crown-8, for interfacial host-guest complexation in inverted perovskite solar cells based on methylammonium and methylammonium-free formamidinium-cesium halide perovskite compositions. Upon post-treatment of the perovskite films, we observed nanostructures on the surface that were associated with the reduced amount of trap states at the interface with the electron transport layer. As a result, we demonstrate improved efficiencies and operational stabilities following ISOS-D-2I and ISOS-L-2I protocols, demonstrating the viability of this approach to advance device stability.

Silver Recovery from Crystalline Silicon Photovoltaic Solar Cells using Continuous Stirred-Tank Reactors.

Silver can be recycled from the end-of-life (EoL) crystalline silicon (c-Si) photovoltaic (PV), yet the recycling and its technology scale-up are still at an early stage especially in continuously stirred tank reactors (CSTR). In this work, the silver recovery from the solar cells is technically understood and optimised in the CSTR system from the point of view of silver recovery efficiency, through integrating experimental and numerical investigations. Specifically, based on the experiments, a kinetics model is developed and SEM surface morphology is characterised; and a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) particle-scale model is integrated with the kinetics model and validated against the fluid-flow pattern and silver leaching performance results from lab measurements. The validated CFD-DEM model is then applied to understand the particle-scale behaviour of silver leaching in the CSTR system in terms of hydrodynamics and AgNO3 distribution under different impeller speeds. The simulation results show that the silver leaching performance is improved in an improved CSTR design with a lower impeller position and doubled impeller layers. This work reveals the effectiveness and underlying hydrodynamics of silver leaching in CSTR systems and lays a foundation for improving silver recovery in PV recycling. This article is protected by copyright. All rights reserved.

High efficiency solar-grade silicon producing by directional solidification through controlling diffusion of impurity

The precise distribution of impurity of the whole silicon ingot is investigated through a theoretical model and the experiments. This model solves the problem of inaccurate prediction of impurity distribution in the final solidification region. The model was used to calculate the distribution of iron impurity in polycrystalline silicon ingots after directional solidification and compared with experiments. The calculation accuracy was significantly improved compared to the traditional Scheil equation. This paper investigates the influence of cooling rate, silicon ingot height and solidification rate on the yield of purified products after directional solidification. For the experimental equipment and raw materials in this paper, the optimal cooling rate of silicon ingots after directional solidification is 0.33 °C/s, the optimal height of silicon ingots is 0.34 m, and the yield of silicon purification increases with the decrease of directional solidification rate. Based on the research results, a standard for removing the top skin of silicon ingots after directional solidification and a method for improving the purification yield by suppressing impurity diffusion during the cooling stage were obtained. This model can provide theoretical guidance for the development of low-cost and high-efficiency methods for removing impurities from polycrystalline silicon, and is of great significance for the development of the photovoltaic industry. In addition, the theoretical model proposed in this paper can also be applied to the directional solidification purification process of other materials, such as the preparation of high-purity aluminum and high-purity titanium, and can predict the impurity migration behavior and distribution pattern throughout the purification process.

The impact of interface recombination on the external quantum efficiency of silicon solar cells

In various types of organic/inorganic solar cells, optical response enhancement is consistently observed within the external quantum efficiency spectra owing to the improvement in interface passivation and the suppression of carrier recombination. In this study, we focused on crystalline silicon solar cells and systematically investigated the impact of interface recombination on the optical response upon dual-side illumination using numerical simulations. The results shed light on the interesting phenomenon that the surface recombination velocity has a significant impact on the external quantum efficiency, and it changes as the illumination direction changes. Moreover, from a practical perspective, the spectra of external quantum efficiency under dual-side illumination conditions can act as a powerful tool for the quick diagnosis of the passivation quality at the top and bottom interfaces.

Insight of Effect of Silver Powders on Silver‐silicon Contacts of Crystalline Silicon Solar Cells through Analysis of Glass Structural Decay

Optimally designed silver‐silicon (Ag‐Si) contacts based on silver (Ag) paste screen printing and the rapid sintering process, have been widely utilized in mainstream crystalline silicon solar cells, enabling to reduce contact resistance and high photo‐conversion efficiency. Ag powder is the largest conductive component in Ag paste, but its impact on the formation of Ag‐Si contacts lacks in‐depth research and comprehensive understanding. In this work, we demonstrated that the oxygen adsorption capacity of silver powders affected the formation of Ag‐Si contacts by enhancing the reactivity of Ag powders with glass frits, and had a significant effect on the performance of devices. The generation of Ag2O introduced by surface absorbed oxygen promoted the transformation of [TeO4] triangular bipyramidal into [TeO3] triangular pyramid, thus destroying the network structure of the glass frits. This structural decay accelerated the spreading of glass frits in the bulk, causing the glass frits to come into contact with SiNx layers earlier and facilitating the formation of the Ag‐Si contacts. This work not only provides a complete picture of the interaction between Ag powder and glass frits, but also a new direction to optimize the Ag‐Si contacts.This article is protected by copyright. All rights reserved.

Experimental investigation of photoelectrical performance and thermal characteristics of ventilated building-integrated photovoltaic system utilizing lightweight and flexible crystalline silicon module

The existing large-scale of industrial buildings with lightweight insulated roofing structures presents a challenge for traditional glass crystalline silicon photovoltaic (PV) systems due to insufficient load-bearing capacity. Meanwhile, traditional PV rooftop applications also face challenges due to limited rooftop resources. To address these issues, this study proposes a ventilated building-integrated lightweight photovoltaic (VL-BIPV) system. The VL-BIPV system incorporates lightweight and flexible crystalline silicon modules, which increase rooftop load by about 6 kg/m2. Additionally, the system features a ventilation channel design to enhance thermal management performance. To evaluate the PV performance and thermal characteristics of the proposed system, an experimental setup was implemented to compare the performances of the VL-BIPV system with a building-attached lightweight photovoltaic (L-BAPV) system that utilizes color steel sheet base plates. The results demonstrate the exceptional performance of VL-BIPV system, with a 100.56% higher ratio of the product of short-circuit current and open-circuit voltage compared to L-BAPV. Moreover, the VL-BIPV system achieved a 1.77% increase in PV efficiency and a 2.35% enhancement in daily electricity generation. In hot weather, the adoption of VL-BIPV reduced the extreme temperature of PV cells by 9.23 °C below 85 °C, surpassing the 6.29 °C reduction achieved by L-BAPV system. Furthermore, the ventilation channel exhibited a gradual temperature increase with slower changes in the flow direction, while the base plate temperature decreased by 13.41 °C, which indicates that VL-BIPV can effectively reduce solar heat gain in the building envelope and improve the indoor thermal environment. The research findings provide important guidance for promoting and applying VL-BIPV technology in large-scale industrial buildings with low rooftop load-bearing capacity, thereby promoting the production and utilization of clean electricity in industrial parks.

Enhancing photovoltaic module sustainability: Defect analysis on partially repaired modules from Spanish PV plants

Between 2010 and 2022, there has been a significant increase in photovoltaic (PV) solar energy installations, driven by factors such as cost reductions, technological advances, policy support and innovative financing approaches. However, this rapid growth has created a significant challenge in the form of increased PV waste generation, coinciding with global commitments to achieve carbon neutrality by 2050. The potential for reuse of decommissioned PV modules represents an environmentally sustainable way forward that requires a comprehensive assessment of technical, economic, environmental and regulatory considerations. This study focuses on evaluating the impact of defects in partially repaired PV modules from Spanish installations on their power output and efficiency, with the aim of developing strategies to increase reuse and reduce environmental impact. The research focuses on 23 crystalline silicon modules and uses established techniques to evaluate their operational condition, detect defects and assess potential safety risks. Among the defects observed, moisture-induced degradation (MID) emerges as the most prevalent, followed by cracked cells and disconnected areas in cells across different technologies. Notably, despite the presence of defects, approximately 87 % of these modules have a power loss of less than 20 %.

Detailed modeling and numerical analysis of thermo mechanical stresses in the crystalline silicon and thin film PV modules under varying climatic conditions

The present manuscript provides an in-depth analysis of the modeling and simulation of thermo-mechanical stresses in photovoltaic panels using finite element (FEM) analysis. It covers important aspects such as the choice of the model, including governing equations, boundary conditions, and simplifying assumptions. The study mainly focuses on evaluating the impact of environmental conditions on the thermo-mechanical stresses of first-generation c-Si and second-generation thin-film CdTe and a-Si PV panels in five different climatic zones in Algeria. The proposed transient 3D numerical model is validated against experimental measurements by other researchers and the tabulated values of the nominal operating temperature of the cell (NOCT). The obtained results indicate that the first principle stress for the c-Si cell is lower compared to CdTe and a-Si cells; this can be explained by looking at the thickness, as well as the Young modulus of the solar cell. Consequently, in regions or countries with hot climatic conditions or large temperature gradients, it is recommended to use PV panels based on first-generation c-Si cells with glass-glass as the front and back covers.

The influence of temperature on spectral characteristics of silicon photovoltaic cells

The influence of temperature on spectral characteristics of silicon photovoltaic cells

Influence of inverted pyramid texturization on front metallization and performance of crystalline silicon solar cells

The silicon surface texturing is an essential part for the fabrication of crystalline silicon solar cells to increase the conversion efficiency. By adjusting the etching texturing condition, inverted pyramid (IP) and upright pyramid (UP) texturization were prepared on crystalline silicon substrates for fabrication of PERC solar cells. The surface morphology not only affects the light trapping but also impacts electrode shading loss and front electrode contact interface. The IP texturization presents better anti-reflective performance due to more common light paths and narrower silver grids owing to less flow of Ag paste on concave blocked structure, both of which results in the higher short-circuit current density (Jsc). Yet in terms of front Ag/Si contact interface, the IP texturization causes more Ag crystallites and more surface recombination under the present condition suitable for UP texturization because of more edges on the upper part of IP, which leads to the lower open-circuit voltage (Voc). The final conversion efficiency of IP solar cells (23.61 %) is 0.06 % higher than that of UP solar cells (23.55 %). An improvement about 0.07 mA/cm2 of Jsc was achieved with IP samples and Voc has a decrease of 0.3 mV caused by the surface recombination on IP texturization. In summary, the structural characteristics of IP results in lower reflectivity and less electrode shading, while Ag/Si contact interface could be optimized by adjusting the processing condition, ultimately promising the higher efficiency.

Crystalline Silicon Photocathode with Tapered Microwire Arrays Achieving a High Current Density of 41.7 mA cm⁻2

AbstractTo design a high‐efficiency crystalline silicon (c‐Si) photocathode, the photovoltage and photocurrent generated by the device must be maximized because these factors directly affect the hydrogen evolution reaction (HER). In this study, a c‐Si p–n junction is used to enhance the photovoltage of the c‐Si photocathode, and a tapered microwire array structure is introduced to increase the photocurrent. When tapered microwire arrays are employed on the front surface of the c‐Si photocathode, a current density of ≈41.7 mA cm−2 is achieved at 0 VRHE (reversible hydrogen electrode); this current density is the highest among all reported photocathodes including c‐Si, approaching the theoretical maximum value for c‐Si. Furthermore, a Ni foil/Pt catalyst is introduced on the opposite side of the incident light, simultaneously serving as an electrocatalyst to reduce side reactions in the HER and encapsulation layer to prevent c‐Si from contacting the electrolyte. Thus, a stable device is developed using c‐Si photoelectrochemical cells that have an efficiency exceeding 97% for >1000 h.

Theoretical Analysis and Simulation of SiO2 and ZrO2 Based Antireflective Coatings to Improve Crystalline Silicon Solar Cell Efficiency

The Solar cell efficiency is crucial, and optical losses can hinder it significantly. Anti-reflective coatings are effective in minimizing these losses. In our study, we used Fresnel equations to calculate reflectance values for single-layer SiO2, ZrO2, a SiO2-ZrO2 mixture, and a double-layer SiO2/ZrO2 configuration. We then assessed their impact on crystalline silicon solar cells using the SCAPS program. The reflectance values of single-layer SiO2, ZrO2 and 10%SiO2-90%ZrO2 mixture were calculated as 19.17%, 13.09% and 13.01%, respectively. Notably, the double-layer SiO2/ZrO2 coating showed a low reflectance of 7.58%, a significant improvement compared to uncoated silicon at 37.45%. Efficiency values for crystalline silicon solar cells were calculated for single layer as 18,95% (SiO2), 20.39% (ZrO2), 20,40% (mixed coating) respectively and 21.68% for the double-layer SiO2/ZrO2 configuration.

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.

Polarization and kinetics of optical emission during laser induced periodic surface structure formation on crystalline silicon

Polarization and kinetics of secondary optical emission, which occurs during the formation of laser-induced periodic surface structures (LIPSSs) on crystalline silicon by a femtosecond laser beam in air, were analyzed. It was found that the emission lines of ablated Si atoms and formed in plasma SiN molecules are unpolarized, and they decay on the nanosecond scale. The second harmonic generation (SHG) is enhanced by laser-induced surface plasmons, and the SHG polarization basically repeats the polarization of the laser. The results can be used for optical monitoring of LIPSS formation in real time, which is especially important for laser processing of large non-planar surfaces.

Anisotropy of the conductivity of silicon nanowires

ABSTRACT This study reports the findings from an investigation into charge carrier transport within a silicon nanowire layer. The samples were prepared using the metal-assisted chemical etching method applied to crystalline silicon wafers with a resistance of 10–20 Ω·cm. The resulting silicon nanowires had a diameter of about 100 nm with a resistance of approximately 15 kΩ·cm. Electrical conductivity measurements were performed in both planar and sandwich configurations, revealing analogous conductivity mechanisms across different geometries. Frequency-dependent conductivity studies unveiled the presence of hopping conductivity. A hypothesis is proposed regarding the existence of a potential barrier at the interface between the nanowire layer and the substrate.

High performance GaAs ultrathin film solar cell based on optimized antireflection coating and dielectric nano-cylinders

This study presents an ultrathin crystalline GaAs solar cell consists of titanium dioxide (TiO2) nano-cylinders partially embedded in the GaAs film and covered by a proper antireflection coating. For light trapping over the solar spectrum and consequently, enhancing the optical and electrical characteristics of the cell, the thickness and refractive index (RI) of the antireflection coating and the embedding depth of the nano-cylinders in the GaAs film have been optimized. Also, aluminum (Al) metallic layer is applied at the backside of the cell to obtain a higher absorption at longer wavelengths due to photon reflection into the GaAs film. In the suggested solar cell, improvements of 70.65 % and 78.12 % in the short current density (JSC) and the power conversion efficiency are obtained, respectively compared to the conventional GaAs solar cell (Case 1).