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Fate and Exposure Assessment of Pb Leachate from Hypothetical Breakage Events of Perovskite Photovoltaic Modules
Abstract
Emerging lead halide perovskite (LHP) photovoltaics are undergoing intense research and development due to their outstanding efficiency and potential for low manufacturing costs that render them competitive with existing photovoltaic (PV) technologies. While today's efforts are focused on stability and scalability of LHPs, the toxicity of lead (Pb) remains a major challenge to their large-scale commercialization. Here, we present a screening-level, EPA-compliant model of fate and transport of Pb leachate in groundwater, soil, and air, following hypothetical catastrophic breakage of LHP PV modules in conceptual utility-scale sites. We estimated exposure point concentrations of Pb in each medium and found that most of the Pb is sequestered in soil. Exposure point concentrations of Pb from the perovskite film fell well below EPA maximum permissible limits in groundwater and air even upon catastrophic release from PV modules at large scales. Background Pb levels in soil can influence soil regulatory compliance, but the highest observed concentrations of perovskite-derived Pb would not exceed EPA limits under our assumptions. Nonetheless, regulatory limits are not definitive thresholds of safety, and the potential for increased bioavailability of perovskite-derived Pb may warrant additional toxicity assessment to further characterize public health risks.
... Food security for the perovskite agrivoltaics should be systematically evaluated due to the Pb-related risks. Certainly, the concern of Pb leaching from perovskite solar cells in the case of encapsulation failure introduces a specific challenge to the application of perovskite agrivoltaics, 176,177 particularly as crops are grown directly beneath the panels. It is crucial to implement effective safeguards to monitor and prevent the inadvertent release of lead leachate, ensuring the protection of agricultural productivity and environmental health. ...
Halide perovskite photovoltaics (PVs) are poised to become a critical high-efficiency renewable energy technology in the fight against climate change. This perspective aims to ensure the viability of perovskite PV...
... Preliminary work has found potential risks from lead, cadmium, or selenium from singlejunction CdTe or perovskite modules during disposal were below U.S. regulatory thresholds at the estimated worst-case risk. 158,159 Similar work has shown that fire and potential impacts to soil and groundwater are below risk-based screening levels and maximum contaminate levels. 160 Given the energy benefits these thin-film PV technologies promise to deliver, there is an argument to be made about responsibly packaging and disposing of modules but not letting concerns preclude deployment of these technologies. ...
... Lead leakage from the module and the use of hazardous solvents in manufacturing are the two major concerns for perovskite-based tandem PVs (99), but they might be mitigated by module inspection and replacement before catastrophic failure. Moreover, recent studies have argued that in the case of catastrophic module failure, the environmental impact will only be moderate (100,101). For solution-processed perovskites, toxicity concerns arising from the solvents [such as dimethylformamide (DMF) and dimethyl sulphoxide (DMSO)] should be mitigated through waste management and purification and recycling processes (102). ...
Perovskite/silicon tandem solar cells offer a promising route to increase the power conversion efficiency of crystalline silicon (c-Si) solar cells beyond the theoretical single-junction limitations at an affordable cost. In the past decade, progress has been made toward the fabrication of highly efficient laboratory-scale tandems through a range of vacuum- and solution-based perovskite processing technologies onto various types of c-Si bottom cells. However, to become a commercial reality, the transition from laboratory to industrial fabrication will require appropriate, scalable input materials and manufacturing processes. In addition, perovskite/silicon tandem research needs to increasingly focus on stability, reliability, throughput of cell production and characterization, cell-to-module integration, and accurate field-performance prediction and evaluation. This Review discusses these aspects in view of contemporary solar cell manufacturing, offers insights into the possible pathways toward commercial perovskite/silicon tandem photovoltaics, and highlights research opportunities to realize this goal.
Background
Lead-based perovskite nanoparticles (Pb-PNPs) are widely utilized in the photovoltaic industry. However, due to their poor stability and high water solubility, lead often gets released into the environment, which can negatively impact the development of the central nervous system (CNS). As an extension of the CNS, the effects and mechanisms of Pb-PNPs on human retinal development have remained elusive.
Objectives
We aimed to investigate the effects of Pb-PNPs on human retinal development.
Methods
Human embryonic stem cell-derived three-dimensional floating retinal organoids (hEROs) were established to simulate early retinal development. Using immunofluorescence staining, biological-transmission electron microscopy analysis, inductively coupled plasma-mass spectrometry, two-dimensional element distribution detection, and RNA sequencing, we evaluated and compared the toxicity of CsPbBr3 nanoparticles (a representative substance of Pb-PNPs) and Pb(AC)2 and investigated the toxicity-reducing effects of SiO2 encapsulation.
Results
Our findings revealed that CsPbBr3 nanoparticles exposure resulted in a concentration-dependent decrease in the area and thickness of the neural retina in hEROs. Additionally, CsPbBr3 nanoparticles exposure hindered cell proliferation and promoted cell apoptosis while suppressing the retinal ganglion cell differentiation, an alteration that further led to the disruption of retinal structure. By contrast, CsPbBr3 nanoparticles exposure to hEROs was slightly less toxic than Pb(AC)2. Mechanistically, CsPbBr3 nanoparticles exposure activated endoplasmic reticulum stress, which promoted apoptosis by up-regulating Caspase-3 and inhibited retinal ganglion cell development by down-regulating Pax6. Interestingly, after coating CsPbBr3 nanoparticles with silica, it exhibited lower toxicities to hEROs by alleviating endoplasmic reticulum stress.
Conclusion
Overall, our study provides evidence of Pb-PNPs-induced developmental toxicity in the human retina, explores the potential mechanisms of CsPbBr3 nanoparticles’ developmental toxicity, and suggests a feasible strategy to reduce toxicity.
Graphical abstract
Emerging lead-based perovskite photovoltaics (PPVs) have attracted rigorous attention as their power-conversion efficiency reached record efficiencies through solution processing of abundant materials. Given that PPVs are also compatible with high volume manufacturing techniques (such as roll-to-roll production), they could be suitable for terawatt production, accelerating a green energy transition, if sustainably commercialized. However, the toxicity of lead causes concern about its use at large scales. In this article, life-cycle analysis (LCA) is used to provide insights into the human and eco-toxicity impact potential of lead-based perovskite solar cells, considering various, material, and process alternatives, with contribution analysis elucidating the most impactful contributors. It was found that silver and indium, not lead, are the major PPV toxicity potential impact contributors. However, a comparison of the “cradle-to-gate” PPV life-cycle impacts per square meter of panel, with those of commercial silicon and thin-film PV, shows that the former have lower potential toxicity impacts than the currently commercial PV.
Solar energy is the fastest-growing source of electricity generation globally. As deployment increases, photovoltaic (PV) panels need to be produced sustainably. Therefore, the resource utilization rate and the rate at which those resources become available in the environment must be in equilibrium while maintaining the well-being of people and nature. Metal halide perovskite (MHP) semiconductors could revolutionize PV technology due to high efficiency, readily available/accessible materials and low-cost production. Here we outline how MHP-PV panels could scale a sustainable supply chain while appreciably contributing to a global renewable energy transition. We evaluate the critical material concerns, embodied energy, carbon impacts and circular supply chain processes of MHP-PVs. The research community is in an influential position to prioritize research efforts in reliability, recycling and remanufacturing to make MHP-PVs one of the most sustainable energy sources on the market.
Perovskite solar cells (PSCs) represent new-generation solar technology, demonstrating attractive properties of low material cost and simple fabrication. Beneficial from remarkable conversion efficiency and improved stability, PSC exhibits high potential...
Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2022 are reviewed. An appendix describing temporary electrical contacting of large‐area solar cells approaches and terminology is also included.
Efficient and stable perovskite solar cells rely on the use of Pb species potentially challenging the technologies’ commercialisation. In this study, the fate of Pb derived from two common perovskite precursors is compared to cationic lead in soil-water microcosm experiments under various biogeochemical conditions. The rapid and efficient removal of Pb from the aqueous phase is demonstrated by inductively coupled plasma mass spectrometry. Sequential soil extraction results reveal that a substantial amount of Pb is associated with immobile fractions, whereas a minor proportion of Pb may become available again in the long term, when oxygen is depleted (e.g. during water logging). X-ray absorption spectroscopy results reveal that the sorption of Pb on mineral phases represents the most likely sequestration mechanism. The obtained results suggest that the availability of leached Pb from perovskite solar cells is naturally limited in soils and that its adverse effects on soil biota are possibly negligible in oxic soils. All three Pb sources used behaved very similar in the experiments, wherefore we conclude that perovskite derived Pb will have a similar fate compared to cationic Pb, so that established risk assessment considerations for Pb remain legitimate.
Solar photovoltaics (PV) are the fastest growing renewable energy technologies for clean, cheap, and sustainable electricity generation. To prepare for rapid scale‐up, the PV industry needs to project material requirements to build out all aspects of the supply chain appropriately and plan to handle large volumes of module waste. Impacts of deploying different material circularity strategies to reduce waste and conserve primary resources need to be quantified to inform sustainable material management. Here, we introduce the photovoltaic dynamic material flow analysis (PV DMFA) model based on PV electricity generation. The model quantifies material flows and stocks in the cradle‐to‐cradle life cycles of utility‐scale c‐Si PV systems in the United States through 2100. We present case studies for solar flat glass and aluminum frame materials under various scenarios to project the impacts of PV performance, reliability, and processing parameters, material circularity strategies, and module design shifts. In the absence of circularity measures, ~100 million MT of flat glass and ~12 million MT of aluminum would be needed for PV installations by 2100 to meet projected growth in domestic utility PV demand to nearly 1000 TWh in 2100. With optimistic but feasible improvements in efficiency, reliability, and circularity, material intensity and waste could be reduced by nearly 50%. Efficient module collection, minimally intrusive recycling, and careful scrap handling and cleaning could improve material circularity in the PV value chain. This model serves as a sustainability data support tool that may aid in the circular economy transition for PV systems.
Photovoltaics (PV), or solar electricity generation, has become the cheapest form of energy in many locations worldwide and, combined with energy storage, has the potential to satisfy most of our electricity needs. PV has grown at an annual compounded growth rate of approximately 30% in the last three decades. Solar energy systems will continue their impressive growth in distributed energy, microgrids, and utility scale, as efforts are made for dependable electricity in an age with increasing extreme weather. However, within this remarkable success lies a new challenge. The growth curve, combined with rapid product innovation and scale up, means that the majority of PV systems are new, without the three years of performance data that have been required in the past to estimate product lifetime. PV reliability has to address this challenge. In this review we present a brief summary of PV reliability starting with brief historical synopsis, detailing some of the technological challenges and present a framework required for long lifetime.
Lead (Pb) is one of the most toxic elements in existence and has been used by humans for thousands of years. With only a few exceptions, each widespread application of lead has been banned systematically due to dramatic environmental and health consequences. However, we are now at the dawn of the perovskite era, potentially requiring yet again the widespread application of lead.
Identifying the distribution of soil lead (Pb) in urban areas can serve to quantify the location and magnitude of health risks, and thereby inform urban land use and Pb mitigation policies. We evaluated total soil Pb distribution across the third largest metropolitan region of the United States (U.S.), Chicago, a city with multiple historical sources of Pb deposition and previous reports of soil total Pb that exceeds geogenic concentrations by orders of magnitude. Total Pb was quantified in Chicago soils obtained by grid sampling (n = 995) parkways and residential properties (n = 156). As anthropogenic modification of soils that entail Pb accumulation may also alter other properties, soil pH, clay content, and Olsen P were also measured. Median and mean total Pb was 220 and 282 mg kg⁻¹ for parkway soils, and 146 and 352 mg kg⁻¹ for residential soils. For parkway soils, 93% of the city area exceeded the conservative CA EPA threshold of 80 mg kg⁻¹ but 94% of the area was below the U.S. EPA threshold of 400 mg kg⁻¹. Hotspots of soil Pb exceeding the U.S. EPA inhalation risk threshold of 400 mg kg⁻¹ occurred for an estimated area of ≈ 38 km², representing ≈ 6% of the total area of 606 km². Soil Pb distributions based on parkway sampling were higher by 100 mg kg⁻¹ or more for ≈ 23% of the city compared to residential sampling. Soil properties of Olsen P, pH, clay, sand, and silt were not found to be related to total Pb concentrations, though a significant negative linear relationship between Olsen P and soil pH was found for 13% of combined soil sampling locations. Across Chicago, the majority of soils in parkways and residential properties appear to be enriched in total Pb concentrations, indicating widespread but non-severe contamination.
Highly-efficient solar cells containing lead halide perovskites are expected to revolutionize sustainable energy production in the coming years. Perovskites are generally assumed to be toxic because of the lead (Pb), but experimental evidence to support this prediction is scarce. We tested the toxicity of the perovskite MAPbI3 (MA = CH3NH3) and several precursors in Arabidopsis thaliana plants. Both MAPbI3 and the precursor MAI hamper plant growth at concentrations above 5 μM. Lead-based precursors without iodide are only toxic above 500 μM. Iodine accumulation in Arabidopsis correlates with growth inhibition at much lower concentrations than lead. This reveals that perovskite toxicity at low concentrations is caused by iodide ions specifically, instead of lead. We calculate that toxicity thresholds for iodide, but not lead, are likely to be reached in soils upon perovskite leakage. This work stresses the importance to further understand and predict harmful effects of iodide-containing perovskites in the environment.
Rapid, terawatt-scale deployment of photovoltaic (PV) modules is required to decarbonize the energy sector. Despite efficiency and manufacturing improvements, material demand will increase, eventually resulting in waste as deployed modules reach end of life. Circular choices for decommissioned modules could reduce waste and offset virgin materials. We present PV ICE, an open-source python framework using modern reliability data which tracks module material flows throughout PV lifecycles. We provide dynamic baselines capturing PV module and material evolution. PV ICE includes multimodal end of life, circular pathways, and manufacturing losses. We present a validation of the framework and a sensitivity analysis. Results show that manufacturing efficiencies strongly affect material demand, representing >20% of the 9 million tonnes of waste cumulatively expected by 2050. Reliability and circular pathways represent the best opportunities to reduce waste by 56% while maintaining installed capacity. Shorter-lived modules generate 81% more waste and reduce 2050 capacity by 6%.
Perovskite photovoltaics are gaining increasing common ground to partner with or compete with silicon photovoltaics to reduce cost of solar energy. However, a cost-effective waste management for toxic lead (Pb), which might determine the fate of this technology, has not been developed yet. Here, we report an end-of-life material management for perovskite solar modules to recycle toxic lead and valuable transparent conductors to protect the environment and create dramatic economic benefits from recycled materials. Lead is separated from decommissioned modules by weakly acidic cation exchange resin, which could be released as soluble Pb(NO3)2 followed by precipitation as PbI2 for reuse, with a recycling efficiency of 99.2%. Thermal delamination disassembles the encapsulated modules with intact transparent conductors and cover glasses. The refabricated devices based on recycled lead iodide and recycled transparent conductors show comparable performance as devices based on fresh raw materials. Cost analysis shows this recycling technology is economically attractive.
Perovskite photovoltaics reached record efficiencies in the laboratory, and if sustainably commercialized, they would accelerate a green energy transition. This article presents the development of life cycle inventory material and energy databases of four most promising single‐junction and three tandem scalable perovskite systems with assumptions regarding scalable production validated by industry experts. We conducted comprehensive “ex ante” life cycle analysis (LCA) and net energy analysis, analyzing their cumulative energy demand, global warming potential profiles, energy payback times, and energy return on investment (EROI). LCA contribution analysis elucidates the most impactful material and process choices. It shows that solution‐based perovskite manufacturing would have lower environmental impact than vapor‐based methods, and that roll‐to‐roll (RtR) printing offers the lowest impact. Among material choices, MoOx/Al has lower impact than Ag, and fluorine‐tin‐oxide lower than indium‐tin‐oxide. Furthermore, we compare perovskites with commercial crystalline‐silicon and thin‐film PV, accounting for the most recent developments in crystalline‐Si wafer production and differences in life expectancies and efficiencies. It is shown that perovskite systems produced with RtR manufacturing could reach in only 12 years of life, the same EROI as that of single‐crystalline‐Si PV lasting 30 years. This work lays a foundation for sustainability investigations of perovskite large‐scale deployment.
Effective recycling of spent perovskite solar modules will further reduce the energy requirements and environmental consequences of their production and deployment, thus facilitating their sustainable development. Here, through ‘cradle-to-grave’ life cycle assessments of a variety of perovskite solar cell architectures, we report that substrates with conducting oxides and energy-intensive heating processes are the largest contributors to primary energy consumption, global warming potential and other types of impact. We therefore focus on these materials and processes when expanding to ‘cradle-to-cradle’ analyses with recycling as the end-of-life scenario. Our results reveal that recycling strategies can lead to a decrease of up to 72.6% in energy payback time and a reduction of 71.2% in greenhouse gas emission factor. The best recycled module architecture can exhibit an extremely small energy payback time of 0.09 years and a greenhouse gas emission factor as low as 13.4 g CO2 equivalent per kWh; it therefore outcompetes all other rivals, including the market-leading silicon at 1.3–2.4 years and 22.1–38.1 g CO2 equivalent per kWh. Finally, we use sensitivity analyses to highlight the importance of prolonging device lifetime and to quantify the effects of uncertainty induced by the still immature manufacturing processes, changing operating conditions and individual differences for each module. Effective recycling of worn-out perovskite photovoltaic modules could improve their energy and environmental sustainability. The authors perform holistic life cycle assessments of selected solar cell architectures and provide guidelines for their future design.
The derivation of ecological soil quality standards for lead (Pb) that account for soil Pb bioavailability has not yet been performed. Here, such standards are derived based on specific studies on long‐term bioavailability and toxicity of Pb to soil organisms and compilation of field data on bioaccumulation of Pb in earthworms. Toxicity thresholds of Pb to plants, invertebrates or micro‐organisms vary over more than 2 orders of magnitude and the lowest values overlap with the range in natural Pb background concentrations in soil. Soils freshly spiked with Pb2+ salts exhibit higher Pb bioavailability and lower toxic thresholds than long‐term aged and leached equivalents. Comparative toxicity tests on leaching and ageing effects suggest using a factor 4.0 higher soil Pb threshold to correct thresholds of freshly spiked soils. Toxicity for plants, earthworms, and microbial N‐transformation and bioaccumulation of Pb in earthworms increase with decreasing effective cation exchange capacity (eCEC) of the soil and models were derived to normalize data for variation of the eCEC among soils. Suggested ecological quality standards for soil expressed as total soil Pb concentration are lower for Pb toxicity to wildlife via secondary poisoning compared to direct Pb toxicity to soil organisms. Standards for both type of receptors vary by factors of about 4 depending on soil eCEC. The data and models collated in this paper can be used for setting ecological soil quality criteria for Pb in different regulatory frameworks. This article is protected by copyright. All rights reserved.
A promising route to widespread deployment of photovoltaics is to harness inexpensive, highly-efficient tandems. We perform holistic life cycle assessments on the energy payback time, carbon footprint, and environmental impact scores for perovskite-silicon and perovskite-perovskite tandems benchmarked against state-of-the-art commercial silicon cells. The scalability of processing steps and materials in the manufacture and operation of tandems is considered. The resulting energy payback time and greenhouse gas emission factor of the all-perovskite tandem configuration are 0.35 years and 10.7 g CO 2 -eq/kWh, respectively, compared to 1.52 years and 24.6 g CO 2 -eq/kWh for the silicon benchmark. Prolonging the lifetime provides a strong technological lever for reducing the carbon footprint such that the perovskite-silicon tandem can outcompete the current benchmark on energy and environmental performance. Perovskite-perovskite tandems with flexible and lightweight form factors further improve the energy and environmental performance by around 6% and thus enhance the potential for large-scale, sustainable deployment.
Perovskite solar cells (PSCs) have increased in power conversion efficiency in the last 10 years, from ≈3% to now over 25%. While the best perovskite photovoltaics have remarkable efficiencies, the Pb‐based absorber is likely problematic for commercialization due to environmental concerns. To address this inevitable issue, a porous metal–organic framework (MOF) polymer composite is applied, known as FeBTC/PDA that is used in “safe‐by‐design” perovskite solar panels. The material is based on a porous MOF scaffold containing a polymeric metal binding agent. Herein, the activity of this material to sequester lead from several solutions is demonstrated, including simulated perovskite solutions, solutions containing decomposed perovskite thin films, and real‐world solutions obtained from damaged solar cell devices in a range of temperatures and conditions, and contaminated water derived from damaged PSCs is brought below the drinkable standards set by the Environmental Protection Agency (EPA).
Toxicants like Pb in lead-based perovskite solar cells (PSCs) may become available to humans through leaching and transport through water, air, and soil. Here, we summarize the potential toxicity of different substances in PSCs and determine the leaching concentration of typical heavy metals used in PSCs through dynamic leaching tests (DLTs). Extraction fluids for the standard toxicity characteristic leaching procedure, synthetic precipitation leaching procedure, and deionized water were used as the DLT leaching solutions. Results indicated that the leaching concentration of Pb exceeded the hazardous waste limit of 5 mg/L. In addition, Pb was found to continuously leach out in the leaching cycles of water extraction. The findings confirmed that discarded PSCs may release Pb when subjected to water, rain, and landfill leachate. Total organic carbon and chemical oxygen demand analyses indicated that discarded PSCs could increase the oxygen consumption and may release CO2 into the environment.
Perovskite solar cells, as an emerging high-efficiency and low-cost photovoltaic technology1–6, face obstacles on their way towards commercialization. Substantial improvements have been made to device stability7–10, but potential issues with lead toxicity and leaching from devices remain relatively unexplored11–16. The potential for lead leakage could be perceived as an environmental and public health risk when using perovskite solar cells in building-integrated photovoltaics17–23. Here we present a chemical approach for on-device sequestration of more than 96 per cent of lead leakage caused by severe device damage. A coating of lead-absorbing material is applied to the front and back sides of the device stack. On the glass side of the front transparent conducting electrode, we use a transparent lead-absorbing molecular film containing phosphonic acid groups that bind strongly to lead. On the back (metal) electrode side, we place a polymer film blended with lead-chelating agents between the metal electrode and a standard photovoltaic packing film. The lead-absorbing films on both sides swell to absorb the lead, rather than dissolve, when subjected to water soaking, thus retaining structural integrity for easy collection of lead after damage. Using lead-absorbing materials to coat the front and back of perovskite solar cells can prevent lead leaching from damaged devices, without affecting the device performance or long-term operation stability.
Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis. Reliability of stability data for perovskite solar cells is undermined by a lack of consistency in the test conditions and reporting. This Consensus Statement outlines practices for testing and reporting stability tailoring ISOS protocols for perovskite devices.
Regulations currently in force enable to claim that the lead content in perovskite solar cells is low enough to be safe, or no more dangerous, than other electronics also containing lead. However, the actual environmental impact of lead from perovskite is unknown. Here we show that the lead from perovskite leaking into the ground can enter plants, and consequently the food cycle, ten times more effectively than other lead contaminants already present as the result of the human activities. We further demonstrate that replacing lead with tin represents an environmentally-safer option. Our data suggest that we need to treat the lead from perovskite with exceptional care. In particular, we point out that the safety level for lead content in perovskite-based needs to be lower than other lead-containing electronics. We encourage replacing lead completely with more inert metals to deliver safe perovskite technologies. Halide perovskites are promising for next generation photovoltaic technology but their environmental impact has not been fully evaluated. Here Li et al. show that the lead from perovskites is ten times more dangerous than lead-containing electronics while tin perovskites are much less bioavailable.
In recent years, the major factors that determine commercialization of perovskite photovoltaic technology have been shifting from solar cell performance to stability, reproducibility, device upscaling and the prevention of lead (Pb) leakage from the module over the device service life. Here we simulate a realistic scenario in which perovskite modules with different encapsulation methods are mechanically damaged by a hail impact (modified FM 44787 standard) and quantitatively measure the Pb leakage rates under a variety of weather conditions. We demonstrate that the encapsulation method based on an epoxy resin reduces the Pb leakage rate by a factor of 375 compared with the encapsulation method based on a glass cover with an ultraviolet-cured resin at the module edges. The greater Pb leakage reduction of the epoxy resin encapsulation is associated with its optimal self-healing characteristics under the operating conditions and with its increased mechanical strength. These findings strongly suggest that perovskite photovoltaic products can be deployed with minimal Pb leakage if appropriate encapsulation is employed.
The perovskite solar cell (PSC) is a rapidly advancing solar technology with high efficiencies and low production costs. However, as the PSC contains methylammonium lead iodide (CH3NH3PbI3, MAPbI3) in the light-harvesting active layer, addressing the safety issue of PSCs is an important prerequisite for its commercialization. In this study, the potential hazards of the PSC were investigated with consideration of Pb species released from PSC using an ecotoxicity, cytotoxicity, chronic toxicity, and genotoxicity battery assay. PSC and its degradation products can cause significant toxicity, with PSC being more toxic than the individual degradation products. The order of ecotoxicity and cytotoxicity was found to be Pb2+ > PSC > PbI2 = PbO. Aquatic toxicity of PSC and its degradation products was suggested by Daphnia magna acute, chronic, and genotoxicity results. The current study highlights the non-negligible hazard potentialities of the PSC and its degradation products, as evidenced by our ecotoxicity and cytotoxicity battery assay. Our study indicates that great caution should be taken in the mass production of PSCs and could facilitate proper risk assessment. Based on our study, some considerations on the implementation of the “safe-by-design (SbD)” approach for the sustainable development of PSC technology can be formulated.
Most research on perovskite solar cells has focused on improving power-conversion efficiency and stability. However, if one could refurbish perovskite solar cells, their stability might not be a critical issue. From the perspective of cost effectiveness, if failed, perovskite solar cells could be collected and recycled; reuse of their gold electrodes and transparent conducting glasses could reduce the price per watt of perovskite photovoltaic modules. Herein, we present a simple and effective method for removing the perovskite layer and reusing the mesoporous TiO2 -coated transparent conducting glass substrate via selective dissolution. We find that the perovskite layer can be easily decomposed in polar aprotic solvents because of the reaction between polar aprotic solvents and Pb 2+ cations. After 10 cycles of recycling, a mesoporous TiO2 -coated transparent conducting glass substrate-based perovskite solar cell still shows a constant power-conversion efficiency, thereby demonstrating the possibility of recycling perovskite solar cells.
Methylammonium lead iodide (MAPbI3) perovskite based solar cells have recently emerged as a serious competitor for large scale and low-cost photovoltaic technologies. However, since these solar cells contain toxic lead, a sustainable procedure for handling the cells after their operational lifetime is required to prevent exposure of the environment to lead and to comply with international electronic waste disposal regulations. Herein, we report a procedure to remove every layer of the solar cells separately, giving the possibility to selectively isolate the different materials. Besides isolating the toxic lead iodide, we show that the PbI2 can be reused for the preparation of new solar cells with comparable performance and in this way avoid lead waste. Furthermore, we show that the most expensive part of the solar cell, the conductive glass (FTO), can be reused several times without any reduction in the performance of the devices. With our simple recycling procedure, we address both the risk of contamination and the waste disposal of perovskite based solar cells, while further reducing the cost of the system. This brings perovskite solar cells one step closer to their introduction into commercial systems.
In the last few years, the advent of metal halide perovskite solar cells has revolutionized the prospects of next-generation photovoltaics. As this technology is maturing at an exceptional rate, research on its environmental impact is becoming increasingly relevant.
Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to 1/416% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization.
The bioavailability of organic chemicals in soil and sediment is an important area of scientific investigation by environmental scientists, but it is still poorly understood by regulators and industry working in the environmental sector. Regulators are starting to consider bioavailability within retrospective risk assessment frameworks for organic chemicals: by doing this, realistic decision-making on polluted environments is achievable, rather than relying on the traditional approach of using total extractable concentrations. However, implementation is not straightforward because the developments of bioavailability science have not always been translated into ready-to-use approaches for regulators. Similarly, bioavailability still remains largely unexplored within prospective regulatory frameworks dealing with approval and regulation of organic chemicals. This article discusses bioavailability concepts and methods, as well as possible pathways for the implementation of bioavailability into risk assessment and regulation, and it offers a simple, pragmatic and justifiable approach within retrospective and prospective fields.
Wigle and Lanphear argue that for many toxins widely dispersed in the environment, even very low levels pose health risks.
Efficiency from hole-selective contacts
Perovskite/silicon tandem solar cells must stabilize a perovskite material with a wide bandgap and also maintain efficient charge carrier transport. Al-Ashouri et al. stabilized a perovskite with a 1.68–electron volt bandgap with a self-assembled monolayer that acted as an efficient hole-selective contact that minimizes nonradiative carrier recombination. In air without encapsulation, a tandem silicon cell retained 95% of its initial power conversion efficiency of 29% after 300 hours of operation.
Science , this issue p. 1300
Despite their many advantages, solar photovoltaic (PV) cells used for electricity generation can have negative environmental impacts. The chemicals necessary for their fabrication can be released into the environment during their disposal or following damage, such as that from natural disasters. The principle objective of this study was to assess the leaching potential of chemical species, primarily heavy metals, from perovskite solar cells (PSC), monocrystalline (MoSC) silicon solar cells, and polycrystalline (PoSC) silicon solar cells under worst-case natural scenarios. In all cases, real solar cells were used as opposed to the pure component. The toxicity characteristic leaching procedure (TCLP) was used to analyze the leachates from PSCs to determine the concentrations of major component species. The results showed that broken PSCs released Si, Pb, Al, As, and Ni under TCLP conditions; lead, a major component of PSCs, was released at around 1.0 mg/L at a pH of 4.93, from both broken and unbroken PSCs. However, the concentrations of these elements in the leachate were within the toxicity characteristic (TC) limits. Encapsulation of the PSCs inhibited the release of hazardous substances, but did not completely eliminate the release of metals. TCLP results from broken MoSCs revealed that metals leached at relatively high levels: Al: 182 mg/L, Ni: 7.7 mg/L, and Cu: 3.6 mg/L. The results from broken PoSCs indicated the release of 43.9 mg/L of Cu and 6.6 mg/L of Pb, which are higher than the TC limits. These high levels may be attributed to the welding materials used on the rear side of crystalline-Si (c-Si) solar cells. This study identifies the importance of encapsulating PSCs and the welding materials on the rear side of c-Si solar cells to minimize the release of toxic substances into the environment.
Recently, perovskite solar cells (PSCs) have attracted much attention owing to their high power conversion efficiency (25.2%) and low fabrication cost. However, the short lifetime under operation is the major obstacle for their commercialization. With efforts from the entire PSC research community, significant advances have been witnessed to improve the device operational stability, and a timely summary on the progress is urgently needed. In this review, we first clarify the definition of operational stability and its significance in the context of practical use. By analyzing the mechanisms in established approaches for operational stability improvement, we summarize several effective strategies to extend device lifetime in a layer-by-layer sequence across the entire PSC. These mechanisms are discussed in the contexts of chemical reactions, photo-physical management, technological modification, etc., which may inspire future R&D for stable PSCs. Finally, emerging operational stability standards with respect to testing and reporting device operational stability are summarized and discussed, which may help reliable device stability data circulate in the research community. The main target of this review is gaining insight into the operational stability of PSCs, as well as providing useful guidance to further improve their operational lifetime by rational materials processing and device fabrication, which would finally promote the commercialization of perovskite solar cells.
Nicole Moody, Samuel Sesena, Dane W. deQuilettes, Benjia Dak Dou, Richard Swartwout, Anna Johnson, Udochukwu Eze, Roberto Brenes, Matthew Johnston, Vladimir Bulović, and Moungi G. Bawendi are members of Tata-MIT GridEdge Solar, an interdisciplinary research program at the Massachusetts Institute of Technology working toward scalable design and manufacturing of lightweight, flexible solar cells.
Joseph T. Buchman and Christy L. Haynes are part of the Center for Sustainable Nanotechnology, a multi-institutional partnership aimed at understanding the fundamental chemical and physical processes that govern the transformations and interactions of nanoparticles in the environment.
B.C. is a postdoctoral fellow of the Research Fund Flanders (FWO). A.B. is a Ph.D. fellow of FWO.
Although power conversion efficiency of perovskite solar cells has exceeded 23%, the poor ambient stability of organic-inorganic halide perovskites poses a challenge for their commercialization. Comprehensive understanding of the underlying degradation mechanisms is a crucial step to seek for approaches which can effectively suppress the degradation of perovskites. Herein, on the basis of extensive first-principles calculations, a three-step photo-oxidative degradation mechanism of MAPbI3 at atomic level is revealed. We find that, in dry ambient, the photo-generated superoxide anions (O2-) firstly lead to fast surface oxidation. While further oxidation of perovskite interior is hindered by the solid oxidation product. the fresh water produced in surface oxidation leads to the inner hydration and eventual breakage of MAPbI3 lattice. We devise a practical strategy for protecting MAPbI3 from photo-induced decomposition by anchoring hydrophobic 2-(4-Fluorophenyl)propan-2-amine on the surface of MAPbI3. The surface modification significantly retards the photo-induced decomposition.
In this research, environmental fate modeling (EFM) was studied to evaluate exposed lead-containing compounds in PSCs and their impact on the environment and on humans. Two major accidental situations involving the environment and exposure to compounds were considered plausible scenarios: fire (PbO) and flooding (PbI2). As a result, water systems were deemed the most vulnerable to the toxicity of exposure to lead compounds. In conclusion, the effect of various environmental and human factors should be assessed and safety standards should be established using the most conservative range among various environmental evaluation results.
Lead halide perovskites (LHP) are an emerging class of photovoltaic (PV) materials that have drawn intense interest due to their power conversion efficiencies above 23% and their potential for low-cost fabrication. However, the toxicity of lead causes concern about its use in LHP-PV at large scales. Here, we quantified lead intensity and toxicity potential of LHP-PV in potential commercial production. Lead intensity in LHP-PV life cycles can be 4 times lower and potential toxic emissions can be 20 times lower than those in representative U.S. electricity mixes, assuming that PV operational lifetimes reach 20 years. We introduce the metric “toxicity potential payback time” accounting for toxic emissions in the life cycle of energy cycles, and showed that it is < 2 years for perovskite PVs produced by and displacing the same grid mix. The toxicity potential associated with the energy of manufacturing a PV system dominates that associated with release of embodied lead. Therefore, the use of lead should not preclude commercialization of LHP-PVs. Instead, effort should focus on development of low-energy manufacturing processes and long service lifetimes. Additional detailed investigations are needed to quantify the full life cycle of commercial production of perovskites and to minimize potential emissions.
To determine if there are potential concerns related to the environmental end-of-life impacts of photovoltaic (PV) or quantum-dot display (QD) technologies, the goal of this study was to assess the magnitude of heavy metal leaching using simulated landfill methodologies from devices in an attempt to forecast the lifecycle environmental impacts of subsequent generations QD-enabled PV technologies. The underlying hypotheses are (H1) existing PV and QD thin-film technologies do not release heavy metals at concentrations exceeding RCRA or State of California regulatory limits; and (H2) the disposal of PV and QD thin-film technologies does not exceed Land Disposal Restrictions (LDR). Three task-oriented objectives were completed: (O1) five representative PV panels and two representative thin-film displays with QD technology were obtained from commercial sources; (O2) RCRA Toxicity Characteristics Leaching Procedure (TCLP) tests and California Waste Extraction Tests (WET) were conducted in addition to microwave-assisted nitric acid digestion; and (O3) results were compared to the existing regulatory limits to examine the potential environmental end-of-life concerns. The heavy metal concentrations obtained from PV panels and QD thin-film displays when exposed to simulated landfill environments and extreme case leaching scenarios were generally several orders of magnitude lower than the promulgated standards and probably not of major concerns related to end-of-life safe disposal of these commercially available products. With exception to the findings for lead under the RCRA rules, the results confirmed that PV and QD thin-film technologies do not release heavy metals at concentrations exceeding RCRA or State of California characteristic hazardous waste regulatory limits. However, lead, mercury, and potentially other heavy metal releases have to be monitored to ensure that the disposal of this type of waste is in compliance with RCRA’s LDR requirements and universal treatment standards because the second underlying hypothesis could not be completely supported for the leaching of these heavy metals. It could be anticipated that newer and more sophisticated soldering materials and approaches in the next generation of PV panels would significantly reduce the use of RCRA heavy metals or nanomaterials. However, although the generated data is limited to these representative PV and QD technologies and as such should not be considered applicable to the entire gamete of present-day technologies, these findings suggest that their release from future PV QD technologies would likely be greater from non-end-of-life processes, than from traditional land disposal routes.
Protecting organohalide perovskite thin films from water and ambient humidity represents a paramount challenge for the commercial uptake of perovskite solar cells and, in general, of related optoelectronic devices. Therefore, understanding the perovskite/water interface is of crucial importance. As a step in this direction, here we present ab initio molecular dynamics simulations aimed at unraveling the atomistic details of the interaction between the methylammonium lead iodide (MAPbI3) perovskite surfaces and a liquid water environment. According to our calculations, MAI-terminated surfaces undergo a rapid solvation process, driven by the interaction of water molecules with Pb atoms, which prompts the release of I atoms. PbI2-terminated surfaces, instead, seem to be more robust to degradation, by virtue of the stronger (shorter) Pb–I bonds formed on these facets. We also observe the incorporation of a water molecule into the PbI2-terminated slab, which could represent the first step in the formation of an intermediate hydrated phase. Interestingly, PbI2 defects on the PbI2-terminated surface promote the rapid dissolution of the exposed facet. Surface hydration, which is spontaneous for both MAI- and PbI2-terminated slabs, does not modify the electronic landscape of the former, while the local band gap of the PbI2-exposing model widens by ∼0.3 eV in the interfacial region. Finally, we show that water incorporation into bulk MAPbI3 produces almost no changes in the tetragonal structure of the perovskite crystal (∼1% volume expansion) but slightly opens the band gap. We believe that this work, unraveling some of the atomistic details of the perovskite/water interface, may inspire new interfacial modifications and device architectures with increased stabilities, which could in turn assist the commercial uptake of perovskite solar cells and optoelectronic devices.
The past few years have witnessed a rapid evolution of perovskite solar cells, an unprecedented photovoltaic (PV) technology with both relatively low cost and high power conversion efficiency. In this paper, we perform a life cycle assessment for two types of solution-processed perovskite solar modules to shed light on the environmental performance of this promising class of PVs. One module is equipped with FTO glass, gold cathode, and mesoporous TiO2 scaffold; the other is equipped with ITO glass, silver cathode, and ZnO thin film. We develop comprehensive life cycle inventories (LCI) for all components used in the modules. Based on the LCI results, we conduct life cycle impact assessment for 16 common life cycle impact indicators, Eco-indicator 99, and two sustainable indicators: energy payback time (EPBT) and CO2 emission factor. We compare the results of Eco-indicator 99, EPBT, and CO2 emission factor among existing PV technologies, and further perform uncertain analysis and sensitivity analysis for the two modules. The results demonstrate that perovskite solar modules possess the shortest EPBT, and future research should be directed to improving system performance ratio and device lifetime, and reducing precious metal consumption and energy-intensive operations in order to lower the CO2 emission factor.
The great promise of hybrid organic-inorganic lead halide perovskite (HOIP)-based solar cells is being challenged by its Pb content, and its sensitivity to water. Here, the impact of rain on methyl ammonium lead iodide perovskite films was investigated by exposing such films to water of varying pH values, simulating exposure of the films to rain. The amount of Pb loss is determined, using both gravimetric and Inductively Coupled Plasma Mass Spectrometry measurements. Using our results, the extent of Pb loss to the environment, in case of catastrophic module failure, was evaluated. Although very dependent on module siting, even total destruction of a large solar electrical power generating plant, based on HOIPs, while obviously highly undesirable, is estimated to be far from catastrophic for the environment.
Fires in residential and commercial properties are not uncommon. If such fires involve the roof, photovoltaic arrays mounted on the roof will be exposed to the flames. The amount of cadmium that can be released in fires involving CdTe PV and the magnitude of associated health risks has been debated. The current study aims in delineating this issue. Previous thermogravimetric studies of CdTe, involved pure CdTe and single-glass PV modules. The current study is based on glass–glass CdTe PV modules which are the only ones in the market. Pieces of commercial CdTe photovoltaic (PV) modules, sizes 25×3 cm, were heated to temperatures up to 1100°C to simulate exposure to residential and commercial building fires. The temperature rate and duration in these experiments were defined according to standard protocols. Four different types of analysis were performed to investigate emissions and redistribution of elements in the matrix of heated CdTe PV modules: (1) measurements of sample weight loss as a function of temperature; (2) analyses of Cd and Te in the gaseous emissions; (3) Cd distribution in the heated glass using synchrotron X-ray fluorescence microprobe analysis; and (4) chemical analysis for Cd and Te in the acid-digested glass. These experiments showed that almost all (i.e., 99·5%) of the cadmium content of CdTe PV modules was encapsulated in the molten glass matrix; a small amount of Cd escaped from the perimeter of the samples before the two sheets of glass melted together. Adjusting for this loss in full-size modules, results in 99·96% retention of Cd. Multiplying this with the probability of occurrence for residential fires in wood-frame houses in the US (e.g., 10−4), results in emissions of 0·06 mg/GWh; the probability of sustained fires and subsequent emissions in adequately designed and maintained utility systems appears to be zero. Published in 2005 by John Wiley & Sons, Ltd.
A multimedia partitioning model, implemented on a microcomputer, describes sequentially the environmntal distribution of, animal and human exposure to, and bioconcentration potential of, relatively persistent organic chemicals in southern Ontario. The model depicts the complete pathways of a chemical after release, including distribution in various environmental media of air, water, sediment, soil and food, the chemical availability to herbivores and humans with consequent estimation of exposure, and its bioconcentration potential in human adipose tissue. The calculated exposures can be compared to those which are judged to have toxic or other effects, and a corresponding safety factor can be estimated. The concepts of estimating critical or multiple exposure routes and the effect of regulating environmental emissions are illustrated. In order to treat this complex issue, the model contains a number of simplifying assumptions (which are discussed); thus it gives no better than order-of-magnitude accuracy. Its principal benefit is its quantification and illustration of the entire process of environmental partitioning, exposure and uptake, and comparison with toxicological and other criteria.
Clear adverse effects of blood lead levels >or=10 microg/dL have been documented in children. Given that the majority of US children have levels below 10 microg/dL, clarification of adverse effects below this cutoff value is needed. Our study evaluated the associations between blood lead levels <10 microg/dL and a broad spectrum of children's cognitive abilities. Data were analyzed from 534 children aged 6-10, enrolled in the New England Children's Amalgam Trial (NECAT) from the urban area of Boston, Massachusetts and rural Farmington, Maine. Adjusting for covariates (age, race, socioeconomic status, and primary caregiver IQ), children with 5-10 microg/dL had 5.0 (S.D. 2.3) points lower IQ scores compared to children with blood lead levels of 1-2 microg/dL (p=0.03). Verbal IQ was more negatively affected than performance IQ, with the most prominent decrement occurring in children's vocabulary. Wechsler Individual Achievement Test scores were strongly negatively associated with blood lead levels of 5-10 microg/dL. In adjusted analyses, children with levels of 5-10 microg/dL scored 7.8 (S.D. 2.4) and 6.9 (S.D. 2.2) points lower on reading and math composite scores, respectively, compared to children with levels of 1-2 microg/dL (p<0.01). Finally, levels of 5-10 microg/dL were associated with decreased attention and working memory. Other than associations of lead exposure with achievement, which even persisted after adjustment for child IQ, the most pronounced deficits were in the areas of spatial attention and executive function. Overall, our analyses support prior research that children's blood levels <10 microg/dL are related to compromised cognition and highlight that these may especially be related to academic achievement.
- P Sinha
- G Heath
- A Wade
- K Komoto