As annual photovoltaics (PV) deployment accelerates toward the terawatt scale, the industry faces three linked challenges: material constraints, cost competitiveness, and environmental performance. Conventional frameworks tend to treat these as competing objectives, where gains in one area incur losses in another. Here, we apply a "smart sustainability" framework to demonstrate how targeted design and material strategies can advance multiple objectives simultaneously. We present updated material learning curves and analyse how material intensity, embodied emissions, and energy return on investment (EROI) co-evolve with deployment scale. Silicon and silver demonstrate that sustained reductions in specific consumption can simultaneously lower cost, ease supply pressure, and - particularly in the case of silicon - cut emissions. Advanced metallisation innovations offer promising pathways to sustain this trend, while next-generation cells can introduce new material dependencies. The different frame materials and mounting configurations are also critical factors in optimising PV sustainability. In recent technological advancements, the EROI of PV is expected to further improve to global-average values of >25, far exceeding the minimum EROI threshold required to sustain modern societies. Together, these findings demonstrate that performance and sustainability are not inherently competing objectives - and that system-level optimisation can unlock pathways where all three advance together.

The photovoltaic (PV) industry is transitioning from Passivated Emitter and Rear Contact (PERC) technology to Tunnel Oxide Passivated Contact (TOPCon) solar cells, which offer higher efficiency but require significantly more silver for screen-printed metallisation. This increased silver demand presents challenges for both manufacturing costs and resource sustainability, particularly as PV production scales towards the terawatt level. To address this, we present a silver-lean screen-printing metallisation technology that substantially reduces silver consumption in industrial TOPCon solar cells while maintaining their excellent efficiencies. Our approach utilises a two-step printing process, where a small amount of silver paste is printed as dashes to form contacts with the silicon surface, followed by the printing of floating fingers and busbars with alternative silver-lean pastes. Using this approach, we achieved an 85 % reduction in rear-side silver usage in 25 %-efficient TOPCon cells, with only a marginal efficiency gap (similar to 0.1 %) compared to TOPCon cells with industrial standard metallisation design. We also demonstrated an ultra-low silver consumption of 2 mg/W by implementing our design on both sides of TOPCon cells. With further optimisations in dash pattern design and printing processes, we expect these cells to reach efficiencies comparable to industrial TOPCon cells with standard metallisation designs. Additionally, we identified a negative interaction between Ag dashes and Al fingers during co-firing, highlighting the need for paste development to take full advantage of this metallisation approach. This work demonstrates a practical and industry-relevant approach to reducing silver consumption in screen-printed metallisation, paving the way for more sustainable and cost-effective manufacturing of TOPCon solar cells.

As the photovoltaics industry approaches the terawatt (TW) manufacturing scale, the consumption of silver in screen‐printed contacts must be significantly reduced for all cell architectures to avoid risks of depleting the global silver supply and substantial cost inflations. With alternative metallization techniques (e.g., plating) facing their own challenges for mass production, advancements in the mainstream screen‐printing technology to accelerate the pace of silver reductions are urgently needed. This work presents a silver‐lean screen‐printed contact scheme, providing scope for substantial reductions in silver consumption based on existing industrial screen‐printing capabilities. The initial testing of such a design leads to the fabrication of 24.04% efficient large‐area TOPCon solar cells with 9 mg W −1 silver consumption compatible with existing soldering‐based interconnection technologies, corresponding to a 25% rel reduction in silver usage compared to standard industrial screen‐printed TOPCon solar cells. Upon further optimization in pattern designs and fabrication processes, this silver‐lean design offers a promising pathway toward ultra‐low silver consumption of less than 2 mg W −1 for screen‐printed TOPCon solar cells without sacrificing efficiency.

In recent years, some water electrolysis experiments with high-resolution measurement techniques indicated that a thin liquid microlayer formed beneath a growing hydrogen bubble on the electrode surface. However, a deep understanding of the mass transfer behavior induced by this microlayer also called the direct injection mass transfer and its quantitative contribution to the hydrogen bubble growth were still not elucidated, although some previously qualitative theory studies have always been frequently mentioned. To clarify the mass transfer characteristics, especially the contribution of the direct injection mass transfer, a volume of fluid (VOF) method based algorithm has been developed to simulate mass transfer mechanisms and a single bubble growth behavior. The influence of the applied current and electrode radius was examined. The proposed numerical method was validated with experimental data in open literature. Based on the numerical results, it is found that the structural features of the initial supersaturated concentration layer with necessary supersaturations S, the distributions and evolutions of the current density and the dissolved hydrogen component concentration caused by the fluid convection and diffusion are important factors affecting both the diffusion mass transfer though the bubble interface and the direct injection mass transfer through the microlayer. The relative contributions of the two different mass transfer behaviors to the single hydrogen bubble growth, the dominant mass transfer mechanism as well as the gas evolution efficiency are demonstrated and discussed at various applied current conditions and electrode radius.

An assessment of the bulk material quality of industrial Czochralski (Cz) grown phosphorus‐doped n‐type silicon (Si) wafers along an ingot is reported. The minority charge carrier lifetimes of the Cz‐Si wafer bulk before and after phosphorous (POCl 3 ) diffusion gettering are assessed, by applying room‐temperature superacid surface passivation to avoid any additional gettering or hydrogenation effect. A substantial increase in the bulk lifetime of all of the n‐type Cz‐Si wafers along the ingot is observed, indicating the effectiveness of a gettering step for such wafers and the presence of getterable metallic impurities in these wafers. By experimentally monitoring the lifetime changes upon a gettering anneal and simulating the gettering kinetics based on different metal diffusivities, iron is identified to be a limiting defect, at least for the wafers from the tail part of the ingot. A dissolved iron concentration of is estimated from the bulk lifetimes of the tail wafers. This lifetime kinetics approach is also a demonstration of a new method to identify iron, or other getterable metals with moderate diffusivities such as chromium, in n‐type silicon wafers.

As PV manufacturing heads towards the multi-TW scale, it is required to carefully evaluate a wide range of concepts including not only efficiency and cost but also material consumption to ensure sustainable manufacturing of PV technologies. The rapid growth of PV could significantly increase the demand for several materials required in solar cells such as silver, aluminium, copper and even silicon, thereby causing dramatic price fluctuations. Furthermore, the PV manufacturing capacity would be at risk of being limited by the supply of some scarce metals, e.g. with current industrial implementations - screen printing (SP) metallization, the capacities of PERC and TOPCon could be capped at 377 GW and 227 GW with 20% of global silver supply available to the PV industry. In addition, PV systems have similar to 25-30 years lifespan to ensure low LCOE and emissions. Recycling alone will not provide an immediate solution to overcome the limitation of material consumption in the exponentially growing PV market. It is expected that the Ag usage needs to be reduced to no more than 5 mg/W or even 2 mg/W for all solar cell technologies to allow a multi-TW manufacturing scale without depleting the global silver supply. Therefore, further advancements in metallization technologies are critically and urgently required to significantly reduce the silver consumption of current screen-printed contacts in industrial silicon solar cells. This paper firstly presents a roadmap towards the 5 mg/W and 2 mg/W silver consumption targets with various metallization technologies and screen-printing designs. Subsequently, a hybrid plating on screen-printed metallization design was proposed to improve the performance and reduce the silver consumption of screen-printed contacts. The experimental results have demonstrated up to 1.08%(abs) improvements in fill factor and 0.3%(abs) gains in cell efficiency. In addition, up to 40%(rel) reductions in finger silver consumption have been achieved without any sacrifices in the electrical conductivity of such hybrid screen-printed and plated fingers. This work proposes not only a roadmap but also a promising approach to significantly reduce the Ag demand and benefit sustainable production of industrial screen-printed silicon solar cells in the TW era.

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The post-processing and recycling of silicon cutting scraps in PV industry is of great importance both in environmental remediation and from an economic perspective. In this work, a novel organic-inorganic composite was synthesized by three-step surface modification of nanoporous silicon (NPSi) powder that was etched with Agassisted chemically of kerf loss silicon waste, which showed high-effective extraction of PbII in industrial effluents. The factors that have a decisive influence on its absorption performance, such as original pH value, absorption saturation time, and original concentration of PbII, are studied in detail. The produced adsorbent has a maximum adsorption capacity of 253.3 mg/g for PbII at the ideal circumstances of pH = 6, t = 10 min, and C0 = 300 mg/L. Both the Langmuir isotherm and the pseudo-second-order model exhibit favorable agreement with the adsorption process. In addition, the adsorption mechanism is dominated by chemical chelation and ion exchange reactions between silanol groups and PbII. The EDA-CC-APTES-NPSi still held fantabulous adsorption capacity even after undergoing a consecutive regeneration round. Hence, this study is about contributing to a new recycling idea of silicon cutting waste, as well as providing a potential adsorbent for efficient PbII removal.

The silicon solar cell market is currently dominated by p-type wafers, due to the popularity of the PERC architecture. However, it is predicted that the market share of silicon solar cells fabricated using n-type wafers will increase rapidly in the following ten years. It is common for p-type silicon solar cells to incorporate post-cell hydrogenation processes, either via illuminated annealing or direct current injection, to increase both the efficiency and stability of the cell. In this work, we investigate the effectiveness of illuminated annealing treatments for improving the efficiency of industrial n-type passivated emitter and rear totally diffused (n-PERT) solar cells. The application of a 30 s process at 200 degrees C led to a 50% increase in the effective lifetime of n-PERT samples, which was caused by an improvement in the surface passivation. This translated to an improvement in cell efficiency of about 0.3%abs, primarily due to an increase open-circuit voltage (Voc), of up to 7 mV. Equivalent dark annealing at 200 degrees C displayed similar efficiency enhancements. Interestingly, n-type cells that were impacted by ring defects caused by oxygen precipitates responded more positively to the illuminated annealing when compared to cells that weren't impacted by ring defects. An efficiency enhancement as high as 0.51%abs was observed for an n-PERT solar cell heavily impacted by recombination induced by ring defects. This suggests that illuminated or dark annealing may be a viable route to reduce the impact of ring defects in high efficiency n-type silicon solar cells such as n-PERT and tunnelling oxide passivating contact (TOPCon) solar cells.

Tunnelling oxide passivated contact (TOPCon) solar cells are gaining significant commercial interest, due to the potential for high efficiency. Industrially, this passivated contact scheme is typically coupled with an n-type Czochralski (Cz) wafer. JinkoSolar Holding Co., Ltd. is one of the leading manufacturers that are producing n-type TOPCon solar cells (referred to as 'HOT' cells) on a commercial scale. In this work, the influence of a post-cell hydrogenation step, using illumination from an LED light source, on the performance and stability of n-type TOPCon solar cells is investigated. The incorporation of this additional hydrogenation treatment led to an average efficiency enhancement of 0.64%(abs) on a batch of 50 cells made in an industrial environment. This significant improvement was caused by a 6.9 mV and 1.04%(abs) increase in open-circuit voltage (V-OC) and fill factor (FF), respectively. We also assessed the stability and found almost no light- and elevated temperature-induced degradation (LeTID) in hydrogenated n-type TOPCon cells. Testing at 70 +/- 5 degrees C under 1-sun illumination revealed that the maximum degradation is limited to 0.06%(rel). Following further stability testing, the efficiency increased beyond the initial value, up to 0.4%(rel) increase after 120 h. By incorporating this hydrogenation process into the production, an average line efficiency of 24.08% and V-OC of 707.5 mV was achieved. The champion cell from the batch displayed an efficiency of 24.58%, as certified by measurement at the Chinese Academy of Sciences.

Chapter Contents: 6.1 Hydrogen complexes with other species 6.1.1 Carbon-hydrogen (CH) complexes in silicon 6.1.2 Oxygen-hydrogen (OH) complexes in silicon 6.1.3 Carbon-oxygen-hydrogen (COH) complexes in silicon 6.1.4 Transition metal-hydrogen complexes in silicon 6.1.5 Vacancy-hydrogen complexes in silicon 6.2 Light- and elevated temperature-induced degradation 6.2.1 The impact of LeTID – cells, modules and systems 6.2.2 The key behaviours of LeTID 6.2.2.1 Dependence on firing on degradation extent 6.2.2.2 A universal defect in silicon 6.2.2.3 LeTID dependence on dielectrics 6.2.2.4 LeTID characterisation 6.2.3 The search for the root cause of LeTID 6.2.3.1 Metallic impurities 6.2.3.2 Hydrogen: a growing consensus 6.2.4 The role of hydrogen in LeTID 6.2.4.1 The impact of hydrogenated dielectric films 6.2.4.2 Direct correlation between hydrogen and LeTID 6.2.4.3 Analysis using DLTS 6.2.5 LeTID mitigation 6.2.6 Models for LeTID 6.2.7 LeTID in p-type silicon heterojunction solar cells 6.3 Negative effects due to hydrogen behaviour 6.3.1 Hydrogen-induced contact resistance 6.3.2 Neutralisation of charge and dopants 6.3.3 Formation of hydrogen-induced platelets 6.4 Summary Acknowledgement References

In this article, a significant degradation of the surface passivation was observed in Czochralski silicon (Cz-Si) lifetime samples using effective lifetime measurements during 1 sun illuminated treatment at 130 degrees C-175 degrees C. The samples are passivated by plasma-enhanced chemical vapor deposited silicon nitride (SiNx) and thermally grown silicon oxide (SiO2). Samples showed strong variations in the kinetics of the surface passivation degradation depending on the passivation stacks, phosphorus diffusion, and bulk doping. Recovery of the surface passivation was only observed on samples passivated by a single silicon nitride layer. To further investigate the observed behavior, corona charging capacitance-voltage measurements were performed. It is shown that surface degradation arises from a combination of changes in interface defect density (D-it) and fixed charge density (Q(f)). We show that two separate degradation channels contribute to the degradation in surface passivation, where the fixed charge density continuously declines, while the interface defect density increases to a maximum and subsequently decreases. The decrease in interface defect density leads to a recovery of surface passivation.

In this study, amino group surface-functionalized porous silicon adsorbent was successfully prepared for the first time using diamond wire saw silicon powder (DWSSP) as raw material through copper-assisted chemical etching (Cu-ACE) and organic functional group grafting. Amino-functionalized porous silicon adsorbent (TEPA-GTS-NPSi) can be used for removing As(V) from water. The properties and mechanism of the new adsorbent were characterized by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (FE-SEM), Brunauer–Emmett–Teller analysis (BET), and thermogravimetric analysis (TGA). The concentration of metal ions in the solution was determined by inductively coupled plasma spectrometry. Meanwhile, the effects of initial pH, adsorption time, initial concentration and adsorbent dosage on the removal of As(V) in an aqueous solution were studied by intermittent adsorption experiments. The results showed that the adsorption equilibrium could be reached rapidly after 30 min soaking. Under the optimized pH of 7, the maximum adsorption capacity was 13.2 mg/g, and the minimum adsorption limit was 3 mg/L. The adsorbent shows good adsorption performance after five successive regenerated cycles. Based on the density functional theory (DFT) analysis results, the adsorption mechanism is attributed to hydrogen bond interaction between the NH2 group and As(V) ions.

In this study, the mechanism of enhancing Fe removal from metallurgical grade silicon (MG-Si) by the novel metal-assisted chemical leaching (MACL) purification methods have been investigated. The typical impurity phase Si2Fe was selected to study interface reactions between the impurity phase and lixiviant. Based on density functional theory (DFT), the interactions of HF leaching, CuACL and AgACL on Si2Fe were revealed through studying the evolution behaviors of atom geometric structure, density of states and bond population, which showed that the stability of Si2Fe structure weakened with the orders of AgACL > CuACL > HF leaching. It was found that the lengths of Si-Fe bonds and metallicity of Si2Fe were successively increased when Si2Fe interacted with HF leaching, CuACL and AgACL, respectively. Compared with HF leaching, MACL weakened Si-Fe bond populations and increased H-Fe bond populations, further destroyed the stability of Si2Fe structure. The experimental results showed that the impurity Fe removal rates were 94.30% for HF leaching, 95.75% for CuACL, and 97.27% for AgACL, respectively, which was highly consistent with the theoretical simulation results. The study provides a theoretical basis for enhancing Fe removal from silicon through MACL produces, indicating that MACL methods have a potential application in deep removal of impurity Fe from silicon in the future. (C) 2020 The Author(s). Published by Elsevier B.V.

LONGi Solar Energy Technology Co. Ltd. has achieved 23.83% for a commercial p‐type Cz PERC cell. From a batch of over 40 000 cells, the average line efficiency achieved was 22.5%. R&D studies investigating hydrogenation and degradation show the importance of hydrogenation processes for efficiency improvements and controlling the hydrogen to prevent light‐induced degradation. Such degradation is shown to appear very differently under different illumination and temperature conditions. This degradation impacts VOC, ISC, and especially fill factor. Current injection and thermal anneal can be used to recover the degradation, but the recovery may not be stable. Reducing the hydrogen content within the cell is shown to minimise degradation without sacrificing performance, provided that enough hydrogen is retained to passivate boron‐oxygen defects.

Introduction The phenomena of lightand elevated temperature-induced degradation (LeTID) was first coined by Kersten et al. to describe a degradation mechism observed in multicrystalline silicon passivated emitter and rear cell (PERC) solar cell structures by Ramspeck et al. [1,2]. Although the exact root cause and mechanics behind the degradation is still a topic of heavy debate, there has been increasing evidence to suggest the involvement of hydrogen [3,4]. One peculiar behaviour pertaining to LeTID is that such phenomena was not observed in historical devices such as the aluminium back-surface field (Al-BSF) solar cell. Although it has been postulated that the reason for such degradation in PERC structures is the increase in hydrogen introduced from the additional rear-side aluminium oxide (AlOx:H) and silicon nitride (SiNx:H) films [5], little effort has been put into understanding the impact of the aluminium rearcontact. Aluminium is well known for its ability to getter and segregate defects and bulk impurities [6] and should, in a similar fashion facilitate the removal of interstitial hydrogen from the bulk. Terry et al. in [7] showed a segregation of hydrogen into aluminium crystallized silicon through the use of SIMS measurements. In this work, we investigate the impact of the aluminium rear-contact in PERC structures during metallization fast-firing on subsequent formation of LeTID. We observe a direct correlation between the rear-aluminium contact area, as facilitated through dielectric openings, with the LeTID extent. Samples containing a higher density of PERC contact openings were observed to show reduced LeTID related defect concentrations.

Silicon (Si) has been considered as one of the most promising candidates for the next-generation lithium-ion battery (LIB) anode materials owing to its huge theoretical specific capacity of 4200 mA h g-1. However, the practical application of Si anodes in commercial LIBs is facing challenges because of the lack of scalable and cost-effective methods to prepare Si-based anode materials with proper microstructure and competitive electrochemical performances. Herein, we report a facile and scalable method to produce multidimensional porous silicon embedded with a nanosilver particle (pSi/Ag) composite from commercially available low-cost metallurgical-grade silicon (MG-Si) powder. The unique hybrid structure contributes to fast electronic transport and relieves volume change of silicon during the charge-discharge process. The pSi/Ag composite exhibits a large initial discharge capacity (3095 mA h g-1 at a high current of 1 A g-1), an excellent cycling performance (1930 mA h g-1 at 1 A g-1 after 50 cycles), and outstanding rate capacities (up to 1778 mA h g-1 at a higher current of 2 A g-1). After the samples are modified by reduced graphene oxide, the capacities of the pSi/Ag@RGO composite electrode can still be maintained over 1000 mA h g-1 after 200 cycles. This study provides a simple and effective strategy for production of high-performance anode materials.

The ultra-thin silicon solar devices perform a potential development direction to decrease material usage and thus lowering the expense. The ultra-thin silicon wafer and inverted pyramid structure texturing were completed by one-step Cu-catalyzed chemical etching (CCCE). In this paper, the influence of H2O2 concentration, Cu (NO3)2 concentration, reaction temperature, and etching time on surface geometry, wafer thickness and light trapping were systematically investigated. The conclusion shows that introduce Cu-particles can significantly accelerate the dissolution of the silicon wafer, the thinning rate of 18 μm/min is more 40-times faster than that of conventional KOH thinning system. Inverted pyramid structure covered thin silicon wafer has ultra-low reflectivity of ~0.5% in the spectrum range of 300~1000 nm. The etching and inverted pyramid structure formation mechanism has finally discussed. The current work develops a new approach for thin silicon manufacturing. Which can be precisely managed by adjusting etching parameters that unlock potential applications in the microelectronics and solar cell market.

The surface passivation quality and the bulk lifetime of boron-doped p-type Czochralski silicon wafers were studied in response to dark annealing at 175 degrees C, using in situ effective lifetime measurements. We investigated non-fired and fired silicon nitride (SiNx), aluminum oxide (AlOx) capped with SiNx, and thermally-grown silicon oxide (SiO2). Modulation in surface passivation quality and bulk lifetime was detected only in cases where hydrogen is assumed to be released into the silicon wafer from the dielectric (AlOx/SiNx stack and fired SiNx layer). Interestingly, the degradation of both the surface and the hulk were followed by a recovery. It is also interesting to note that the changes in the surface and the bulk seem to he related, as the surface degradation starts when the initial hulk degradation ends. This study indicates a possible involvement of hydrogen in both the degradation and the recovery processes. The evolution of the effective lifetime as a function of time is similar to that reported for carrier-induced degradation in multicrystalline wafers; however, occurring on a different time scale. Hence, these findings may also be valuable for investigation of other degradation mechanisms in different silicon materials.

Lightand elevated temperature-induced degradation (LeTID) has, in recent years, captured the attention of the global silicon photovoltaics industry. With over 180 publications and countless conference presentations from more than 40 universities, research institutes and manufacturers alike (see Fig. 1), there has been a range of studies conducted to understand the behaviours, kinetics, mitigation strategies and root cause of the defect. In this talk, we will provide a condensed review of the current global progress on LeTID research, highlighting recent theories, models, mitigation strategies and implications on the future of commercial silicon solar cells.