On-device lead sequestration for perovskite solar cells

Air-Processed Efficient Perovskite Solar Cells With Full Lifecycle Management

Despite the outstanding power conversion efficiency of perovskite solar cells (PSCs) realized over the years, the entire lifecycle from preparation and operation to discarding of PSCs still needs to be carefully considered when it faces the upcoming large-scale production and deployment. In this study, bio-derived chitin-based polymers are employed to realize the full lifecycle regulation of air-processed PSCs by forming multiple coordinated and hydrogen bonds to stabilize the lead iodide and organic salt precursor inks, accelerating the solid-liquid reaction and crystallization of two-step deposition process, then achieving the high crystalline and oriented perovskites with less notorious charge defects in the open air. The air-prepared PSCs exhibit a decent efficiency of 25.18% with high preparation reproducibility and improved operational stability toward the harsh environment and mechanical stress stimuli. The modified PSCs display negligible fatigue behavior with keeping 92% of its initial efficiency after operating for 32 diurnal cycles (ISOS-LC-1 protocol). Meanwhile, closed-loop lead management of end-of-life PSCs including suppression of lead leakage, toxicity evaluation of broken devices, and recycling of lead iodide components are comprehensively investigated. This work sheds light on a promising avenue to realize the entire lifecycle regulation of air-processed efficient and stable PSCs.

The Promise and Challenges of Inverted Perovskite Solar Cells

Recently, there has been an extensive focus on inverted perovskite solar cells (PSCs) with a p-i-n architecture due to their attractive advantages, such as exceptional stability, high efficiency, low cost, low-temperature processing, and compatibility with tandem architectures, leading to a surge in their development. Single-junction and perovskite-silicon tandem solar cells (TSCs) with an inverted architecture have achieved certified PCEs of 26.15% and 33.9% respectively, showing great promise for commercial applications. To expedite real-world applications, it is crucial to investigate the key challenges for further performance enhancement. We first introduce representative methods, such as composition engineering, additive engineering, solvent engineering, processing engineering, innovation of charge transporting layers, and interface engineering, for fabricating high-efficiency and stable inverted PSCs. We then delve into the reasons behind the excellent stability of inverted PSCs. Subsequently, we review recent advances in TSCs with inverted PSCs, including perovskite-Si TSCs, all-perovskite TSCs, and perovskite-organic TSCs. To achieve final commercial deployment, we present efforts related to scaling up, harvesting indoor light, economic assessment, and reducing environmental impacts. Lastly, we discuss the potential and challenges of inverted PSCs in the future.

Single Layer of Crown Ether Enables Efficient, Stable, and Pb Leakage-Free Inverted Perovskite Solar Cells

Significant challenges in ensuring long-term stability, addressing environmental safety issues, and improving efficiency have hindered the commercialization of inverted Pb-based halide perovskite solar cells (PeSCs). One reasonable approach to addressing these issues is to place an effective buffer layer between the perovskite active layer and the electrode. In this study, we demonstrate the use of crown ether, di-tert-butyl dibenzo-18-crown-6, as a single buffer layer to improve the efficiency, long-term stability, and environmental safety of PeSCs for the first time. The crown ether buffer layer suppressed Ag diffusion from the Ag metal electrodes, thereby improving the performance and lifetime of the device. In addition, it effectively captures Pb ions that may leak into the environment during the whole lifetime of devices, thereby enhancing the environmental safety of PeSCs. Furthermore, PeSCs incorporating crown ethers as buffer layers demonstrated enhanced stability in a nitrogen atmosphere and achieved a high power conversion efficiency of 22.8%. Consequently, this crown ether buffer layer offers an effective and straightforward strategy capable of achieving efficient, stable, and environmentally safe PeSCs.

Achievements, challenges, and future prospects for industrialization of perovskite solar cells

In just over a decade, certified single-junction perovskite solar cells (PSCs) boast an impressive power conversion efficiency (PCE) of 26.1%. Such outstanding performance makes it highly viable for further development. Here, we have meticulously outlined challenges that arose during the industrialization of PSCs and proposed their corresponding solutions based on extensive research. We discussed the main challenges in this field including technological limitations, multi-scenario applications, sustainable development, etc. Mature photovoltaic solutions provide the perovskite community with invaluable insights for overcoming the challenges of industrialization. In the upcoming stages of PSCs advancement, it has become evident that addressing the challenges concerning long-term stability and sustainability is paramount. In this manner, we can facilitate a more effective integration of PSCs into our daily lives.

Fusing Science with Industry: Perovskite Photovoltaics Moving Rapidly into Industrialization

The organic-inorganic lead halide per materials have emerged as highly promising contenders in the field of photovoltaic technology, offering exceptional efficiency and cost-effectiveness. The commercialization of perovskite photovoltaics hinges on successfully transitioning from lab-scale perovskite solar cells to large-scale perovskite solar modules (PSMs). However, the efficiency of PSMs significantly diminishes with increasing device area, impeding commercial viability. Central to achieving high-efficiency PSMs is fabricating uniform functional films and optimizing interfaces to minimize energy loss. This review sheds light on the path toward large-scale PSMs, emphasizing the pivotal role of integrating cutting-edge scientific research with industrial technology. By exploring scalable deposition techniques and optimization strategies, the advancements and challenges in fabricating large-area perovskite films are revealed. Subsequently, the architecture and contact materials of PSMs are delved while addressing pertinent interface issues. Crucially, efficiency loss during scale-up and stability risks encountered by PSMs is analyzed. Furthermore, the advancements in industrial efforts toward perovskite commercialization are highlighted, emphasizing the perspective of PSMs in revolutionizing renewable energy. By highlighting the scientific and technical challenges in developing PSMs, the importance of combining science and industry to drive their industrialization and pave the way for future advancements is stressed.

Lead-rivet strategy of growing perovskite nanocrystals for excellent toxicity inhibition and spinning application

Lead halide perovskite has demonstrated remarkable potential in the wearable field due to its exceptional photoelectric conversion capability. However, its lead toxicity issue has consistently been subject to criticism, significantly impeding its practical application. To address this challenge, an innovative approach called lead-rivet was proposed for the in-situ growth of perovskite crystalline structures. Through the formation of S-Pb bonds, each Pb2+ ion was firmly immobilized on the surface of the silica matrix, enabling in situ growth of perovskite nanocrystals via ion coordination between Cs+ and halide species. The robust S-Pb bonding effectively restricted the mobility of lead ions and stabilized the perovskite structure without relying on surface ligands, thereby not only preventing toxicity leakage but also providing a favorable interface for depositing protective shells. The obtained perovskites exhibit intense and narrow-band fluorescence with full-width at half-maximum less than 23 nm and show excellent stability to high temperature (above 202 °C) and high humidity (water immersion over 27 days), thus making it possible to be used in varies textile technologies including melt spinning and wet spinning. The lead leakage rate of particles is only 4.15 % demonstrating excellent toxicity inhibition performance. The prepared fibers maintained good extensibility and flexibility which could be used for 3D-printing and textiles weaving. Most importantly, the detected Pb2+ leaching was negligible as low as to 0.732 ppb which meet the standard of World Health Organization (WHO) for drinking water (<10 ppb), and the cell survival rate remained 99.196 % for PLA fluorescent filament after 24 h cultivation which showing excellent safety to human body and environment. This study establishes a controllable and highly adaptable synthesis method, thereby providing a promising avenue for the safe utilization of perovskite materials.

Lead Isolation and Capture in Perovskite Photovoltaics toward Eco-Friendly Commercialization

Perovskite solar cells (PSCs) are developed rapidly in efficiency and stability in recent years, which can compete with silicon solar cells. However, an important obstacle to the commercialization of PSCs is the toxicity of lead ions (Pb2+) from water-soluble perovskites. The entry of free Pb2+ into organisms can cause severe harm to humans, such as blood lead poisoning, organ failure, etc. Therefore, this work reports a "lead isolation-capture" dual detoxification strategy with calcium disodium edetate (EDTA Na-Ca), which can inhibit lead leakage from PSCs under extreme conditions. More importantly, leaked lead exists in a nontoxic aggregation state chelated by EDTA. For the first time, in vivo experiments are conducted in mice to systematically prove that this material has a significant inhibitory effect on the toxicity of perovskites. In addition, this strategy can further enhance device performance, enabling the optimized devices to achieve an impressive power conversion efficiency (PCE) of 25.19%. This innovative strategy is a major breakthrough in the research on the prevention of lead toxicity in PSCs.

Stable and Lead-Safe Polyphenol-Encapsulated Perovskite Solar Cells

Lead (Pb) halide perovskite solar cells (PSCs) exhibit impressive power conversion efficiencies close to those of their silicon counterparts. However, they suffer from moisture instability and Pb safety concerns. Previous studies have endeavoured to address these issues independently, yielding minimal advancements. Here, a general nanoencapsulation platform using natural polyphenols is reported for Pb-halide PSCs that simultaneously addresses both challenges. The polyphenol-based encapsulant is solution-processable, inexpensive (≈1.6 USD m-2), and requires only 5 min for the entire process, highlighting its potential scalability. The encapsulated devices with a power conversion efficiency of 20.7% retained up to 80% of their peak performance for 2000 h and up to 70% for 7000 h. Under simulated rainfall conditions, the encapsulant rich in catechol groups captures the Pb ions released from the degraded perovskites via coordination, keeping the Pb levels within the safe drinking water threshold of 15 ppb.

Ultrafast Photoexcitation Induced Passivation for Quasi-2D Perovskite Photodetectors

Quasi-2D perovskites exhibit great potential in photodetectors due to their exceptional optoelectronic responsivity and stability, compared to their 3D counterparts. However, the defects are detrimental to the responsivity, response speed, and stability of perovskite photodetectors. Herein, an ultrafast photoexcitation-induced passivation technique is proposed to synergistically reduce the dimensionality at the surface and induce oxygen doping in the bulk, via tuning the photoexcitation intensity. At the optimal photoexcitation level, the excited electrons and holes generate stretching force on the Pb─I bonds at the interlayered [PbI6]-, resulting in low dimensional perovskite formation, and the absorptive oxygen is combined with I vacancies at the same time. These two induced processes synergistically boost the carrier transport and interface contact performance. The most outstanding device exhibits a fast response speed with rise/decay time of 201/627 ns, with a peak responsivity/detectivity of 163 mA W-1/4.52 × 1010 Jones at 325 nm and the enhanced cycling stability. This work suggests the possibility of a new passivation technique for high performance 2D perovskite optoelectronics.

Sustainability pathways for perovskite photovoltaics

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.

Triple Cross-Linking Engineering Strategies for Efficient and Stable Inverted Flexible Perovskite Solar Cells

Inverted flexible perovskite solar cells (fPSCs) are promising for commercialization due to their low cost, lightweight, and excellent stability. However, enhancing fPSCs' power conversion efficiency and stability remains challenging. Here, an unprecedented triple cross-linking engineering strategy is innovatively exhibit for efficient and stable inverted fPSCs. First, a carefully designed cross-linker, 4-fluorophenyl 5-(1,2-dithiolan-3-yl) pentanoate (FB-TA), is added to the perovskite precursor solution. During the perovskite film's crystallization at a low temperature, the cross-linking product of FB-TA can passivate the grain boundaries and reduce the film's residual strain and Young's module. Then, FB-TA is also introduced for the bottom- and top-interface modification of the perovskite film. The interfacial treating strategy protects the perovskite from water invasion and strengthens the interfaces. The combination of triple strategies affords highly efficient inverted fPSCs with a champion efficiency of 21.42% among the state-of-the-art inverted fPSCs based on nickel oxides. More importantly, the flexible devices also exhibit superior stabilities with T90 >4000 bending cycles, photostability with T90 >568 h, and ambient stability with T90 >2000 h, especially the stability with T80 >1120 h under harsh damp-heat conditions (i.e., 85 °C and 85% RH). The strategy provides new insights into the industrialization of high-performance and stable fPSCs.

Navigating challenges and solutions for metal-halide and carbon-based electrodes in perovskite solar cells (NCS-MCEPSC): An environmental approach

The urgent need to shift to renewable energy is highlighted by rising global energy use and environmental issues like global warming from fossil fuel dependency. Perovskite solar cells (PSCs) stand out as a promising option, providing high efficiency and potential for cost-effective production. This study delves into the environmental concerns and viable solutions linked with metal-halide PSCs (M-PSCs) and carbon-based electrode PCSs (C-PSCs). It showcases the swift progress in PSC technology, highlighting its potential to deliver efficient and economical renewable energy options. Yet, the environmental implications of these technologies, especially the utilization of toxic lead (Pb) in M-PSCs and the issues of stability and degradation in C-PSCs, represent considerable hurdles for their broad application and sustainability. The paper details the recent advances in PSCs, focusing on enhancements in device efficiency and stability through innovative material combinations and device designs. Nonetheless, the environmental hazards linked to the dispersal of toxic substances from compromised or deteriorating PSCs into the ecosystem raise significant concerns. In particular, the risk of Pb from M-PSCs contaminating soil and aquatic ecosystems is a pressing issue for human and environmental health, spurring investigations into alternative materials and methods to diminish these impacts. The authors examine several strategies, including the introduction of Pb-free perovskites, encapsulation methods to block the escape of hazardous substances, and the recycling of PSC elements. The study stresses the necessity of aligning technological innovations with considerations for the environment and health, calling for ongoing research into PSC technologies that are sustainable and safe. This review highlights the need for detailed assessments of PSC technologies, focusing on their renewable energy contributions, environmental impacts, and strategies to mitigate these effects. The authors call for a cohesive strategy to develop PSCs that are efficient, cost-effective, eco-friendly, and safe for widespread use.

Preventing lead leakage in perovskite solar cells and modules with a low-cost and stable chemisorption coating

Despite the promising commercial prospects of perovskite solar cells, the issue of lead toxicity continues to hinder their future industrial applications. Here, we report a low-cost and rapidly degraded sulfosuccinic acid-modified polyvinyl alcohol (SMP) coating that prevents lead leakage and enhances device stability without compromising device performance. Even under different strict conditions (simulated heavy rain, acid rain, high temperatures, and competing ions), the coatings effectively prevent lead leakage by over 99%. After 75 days of outdoor exposure, the coating still demonstrates similar lead sequestration efficiency (SQE). In addition, it can be applied to different device structures (n-i-p and p-i-n) and modules, with over 99% SQE, making it a general method for preventing lead leakage.

Remanufacturing Perovskite Solar Cells and Modules-A Holistic Case Study

While perovskite photovoltaic (PV) devices are on the verge of commercialization, promising methods to recycle or remanufacture fully encapsulated perovskite solar cells (PSCs) and modules are still missing. Through a detailed life-cycle assessment shown in this work, we identify that the majority of the greenhouse gas emissions can be reduced by re-using the glass substrate and parts of the PV cells. Based on these analytical findings, we develop a novel thermally assisted mechanochemical approach to remove the encapsulants, the electrode, and the perovskite absorber, allowing reuse of most of the device constituents for remanufacturing PSCs, which recovered nearly 90% of their initial performance. Notably, this is the first experimental demonstration of remanufacturing PSCs with an encapsulant and an edge-seal, which are necessary for commercial perovskite solar modules. This approach distinguishes itself from the "traditional" recycling methods previously demonstrated in perovskite literature by allowing direct reuse of bulk materials with high environmental impact. Thus, such a remanufacturing strategy becomes even more favorable than recycling, and it allows us to save up to 33% of the module's global warming potential. Remarkably, this process most likely can be universally applied to other PSC architectures, particularly n-i-p-based architectures that rely on inorganic metal oxide layers deposited on glass substrates. Finally, we demonstrate that the CO2-footprint of these remanufactured devices can become less than 30 g/kWh, which is the value for state-of-the-art c-Si PV modules, and can even reach 15 g/kWh assuming a similar lifetime.

A prospective ecological risk assessment of high-efficiency III-V/silicon tandem solar cells

III-V/Silicon tandem solar cells offer one of the most promising avenues for high-efficiency, high-stability photovoltaics. However, a key concern is the potential environmental release of group III-V elements, especially arsenic. To inform long-term policies on the energy transition and energy security, we develop and implement a framework that fully integrates future PV demand scenarios with dynamic stock, emission, and fate models in a probabilistic ecological risk assessment. We examine three geographical scales: local (including a floating utility-scale PV and waste treatment), regional (city-wide), and continental (Europe). Our probabilistic assessment considers a wide range of possible values for over one hundred uncertain technical, environmental, and regulatory parameters. We find that III-V/silicon PV integration in energy grids at all scales presents low-to-negligible risks to soil and freshwater organisms. Risks are further abated if recycling of III-V materials is considered at the panels' end-of-life.

Indoor Self-Powered Perovskite Optoelectronics with Ultraflexible Monochromatic Light Source

Self-powered skin optoelectronics fabricated on ultrathin polymer films is emerging as one of the most promising components for the next-generation Internet of Things (IoT) technology. However, a longstanding challenge is the device underperformance owing to the low process temperature of polymer substrates. In addition, broadband electroluminescence (EL) based on organic or polymer semiconductors inevitably suffers from periodic spectral distortion due to Fabry-Pérot (FP) interference upon substrate bending, preventing advanced applications. Here, ultraflexible skin optoelectronics integrating high-performance solar cells and monochromatic light-emitting diodes using solution-processed perovskite semiconductors is presented. n-i-p perovskite solar cells and perovskite nanocrystal light-emitting diodes (PNC-LEDs), with power-conversion and current efficiencies of 18.2% and 15.2 cd A-1 , respectively, are demonstrated on ultrathin polymer substrates with high thermal stability, which is a record-high efficiency for ultraflexible perovskite solar cell. The narrowband EL with a full width at half-maximum of 23 nm successfully eliminates FP interference, yielding bending-insensitive spectra even under 50% of mechanical compression. Photo-plethysmography using the skin optoelectronic device demonstrates a signal selectivity of 98.2% at 87 bpm pulse. The results presented here pave the way to inexpensive and high-performance ultrathin optoelectronics for self-powered applications such as wearable displays and indoor IoT sensors.

Self-Healing Behavior of the Metal Halide Perovskites and Photovoltaics

Perovskite solar cells have achieved rapid progress in the new-generation photovoltaic field, but the commercialization lags behind owing to the device stability issue under operational conditions. Ultimately, the instability issue is attributed to the soft lattice of ionic perovskite crystal. In brief, metal halide perovskite materials are susceptible to structural instability processes, including phase segregation, component loss, lattice distortion, and fatigue failure under harsh external stimuli such as high humidity, strong irradiation, wide thermal cycles, and large stress. Developing self-healing perovskites to further improve the unsatisfactory operational stability of their photoelectric devices under harsh stimuli has become a cutting-edge hotspot in this field. This self-healing behavior needs to be studied more comprehensively. Therefore, the self-healing behavior of the metal halide perovskites and photovoltaics is classified and summarized in this review. By discussing recent advances, underlying mechanisms, strategies, and existing challenges, this review provides perspectives on self-healing of perovskite solar cells in the future.

Unraveling the Degradation Pathway of Inverted Perovskite Solar Cells Based on ISOS-D-1 Protocol

Perovskite solar cells (PSCs) have shown rapid development recently, whereas nonideal stability remains the chief obstacle toward commercialization. Thus, it is of utmost importance to probe the degradation pathway for the entire device. Here, the extrinsic stability of inverted PSCs (IPSCs) is investigated by using standard shelf-life testing based on the International Summit on Organic Photovoltaic Stability protocols (ISOS-D-1). During the long-term assessment of 1700 h, the degraded power conversion efficiency is mainly caused by the fill factor (53% retention) and short-circuit current density (71% retention), while the open-circuit voltage still maintains 97% of the initial values. Further absorbance evolution and density functional theory calculations disclose that the perovskite rear-contact side, in particular for the perovskite/fullerene interface, is the predominant degradation pathway. This study contributes to understanding the aging mechanism and enhancing the durability of IPSCs for future applications.

On the Durability of Tin-Containing Perovskite Solar Cells

Tin (Sn)-containing perovskite solar cells (PSCs) have gained significant attention in the field of perovskite optoelectronics due to lower toxicity than their lead-based counterparts and their potential for tandem applications. However, the lack of stability is a major concern that hampers their development. To achieve the long-term stability of Sn-containing PSCs, it is crucial to have a clear and comprehensive understanding of the degradation mechanisms of Sn-containing perovskites and develop mitigation strategies. This review provides a compendious overview of degradation pathways observed in Sn-containing perovskites, attributing to intrinsic factors related to the materials themselves and environmental factors such as light, heat, moisture, oxygen, and their combined effects. The impact of interface and electrode materials on the stability of Sn-containing PSCs is also discussed. Additionally, various strategies to mitigate the instability issue of Sn-containing PSCs are summarized. Lastly, the challenges and prospects for achieving durable Sn-containing PSCs are presented.

Remarkable performance recovery in highly defective perovskite solar cells by photo-oxidation

Exposure to environmental factors is generally expected to cause degradation in perovskite films and solar cells. Herein, we show that films with certain defect profiles can display the opposite effect, healing upon exposure to oxygen under illumination. We tune the iodine content of methylammonium lead triiodide perovskite from understoichiometric to overstoichiometric and expose them to oxygen and light prior to the addition of the top layers of the device, thereby examining the defect dependence of their photooxidative response in the absence of storage-related chemical processes. The contrast between the photovoltaic properties of the cells with different defects is stark. Understoichiometric samples indeed degrade, demonstrating performance at 33% of their untreated counterparts, while stoichiometric samples maintain their performance levels. Surprisingly, overstoichiometric samples, which show low current density and strong reverse hysteresis when untreated, heal to maximum performance levels (the same as untreated, stoichiometric samples) upon the photooxidative treatment. A similar, albeit smaller-scale, effect is observed for triple cation and methylammonium-free compositions, demonstrating the general application of this treatment to state-of-the-art compositions. We examine the reasons behind this response by a suite of characterization techniques, finding that the performance changes coincide with microstructural decay at the crystal surface, reorientation of the bulk crystal structure for the understoichiometric cells, and a decrease in the iodine-to-lead ratio of all films. These results indicate that defect engineering is a powerful tool to manipulate the stability of perovskite solar cells.

Green solvents, materials, and lead-free semiconductors for sustainable fabrication of perovskite solar cells

Perovskite materials research has received unprecedented recognition due to its applications in photovoltaics, LEDs, and other large area low-cost electronics. The exceptional improvement in the photovoltaic conversion efficiency of Perovskite solar cells (PSCs) achieved over the last decade has prompted efforts to develop and optimize device fabrication technologies for the industrial and commercial space. However, unstable operation in outdoor environments and toxicity of the employed materials and solvents have hindered this proposition. While their optoelectronic properties are extensively studied, the environmental impacts of the materials and manufacturing methods require further attention. This review summarizes and discusses green and environment-friendly methods for fabricating PSCs, particularly non-toxic solvents, and lead-free alternatives. Greener solvent choices are surveyed for all the solar cell films, (i.e. electron and hole transport, semiconductor, and electrode layers) and their impact on thin film quality, morphology and device performance is explored. We also discuss lead content in perovskites, its environmental impact and sequestration routes, and progress in replacing lead with greener alternatives. This review provides an analysis of sustainable green routes in perovskite solar cell fabrication, discussing the impact of each layer in the device stack, via life cycle analysis.

Soil adsorption and transport of lead in the presence of perovskite solar cell-derived organic cations

Perovskite photovoltaics offer a highly efficient and low-cost solar energy harvesting technology. However, the presence of lead (Pb) cations in photovoltaic halide perovskite (HaPs) materials is concerning, and quantifying the environmental hazard of accidental Pb²⁺ leaching into the soil is crucial for assessing the sustainability of this technology. Pb²⁺ from inorganic salts was previously found to remain in the upper soil layers due to adsorption. However, Pb-HaPs contain additional organic and inorganic cations, and competitive cation adsorption may affect Pb²⁺ retention in soils. Therefore, we measured, analyzed by simulations and report the depths to which Pb²⁺ from HaPs penetrates into 3 types of agricultural soil. Most of the HaP-leached Pb²⁺ is found to be retained already in the first cm of the soil columns, and subsequent rain events do not induce Pb²⁺ penetration below the first few cm of soil surface. Surprisingly, organic co-cations from the dissolved HaP are found to enhance the Pb²⁺ adsorption capacity in clay-rich soil, compared to non-HaP-based Pb²⁺ sources. Our results imply that installation over soil types with improved Pb²⁺ adsorption, and removal of only the contaminated topsoil, are sufficient means to prevent ground water contamination by HaP-leached Pb²⁺.

Study on myocardial toxicity induced by lead halide perovskites nanoparticles

Lead halide perovskites (LHPs) are outstanding candidates for next-generation optoelectronic materials, with considerable prospects of use and commercial value. However, knowledge about their toxicity is scarce, which may limit their commercialization. Here, for the first time, we studied the cardiotoxicity and molecular mechanisms of representative CsPbBr3 nanoparticles in LHPs. After their intranasal administration to Institute of Cancer Research (ICR) mice, using advanced synchrotron radiation, mass spectrometry, and ultrasound imaging, we revealed that CsPbBr3 nanoparticles can severely affect cardiac systolic function by accumulating in the myocardial tissue. RNA sequencing and Western blotting demonstrated that CsPbBr3 nanoparticles induced excessive oxidative stress in cardiomyocytes, thereby provoking endoplasmic reticulum stress, disturbing calcium homeostasis, and ultimately leading to apoptosis. Our findings highlight the cardiotoxic effects of LHPs and provide crucial toxicological data for the product.

Regulating Crystallization and Lead Leakage of Perovskite Solar Cell Via Novel Polyoxometalate-Based Metal-Organic Framework

Despite the unprecedented progress in lead-based perovskite solar cells (PSCs), the toxicity and leakage of lead from degraded PSCs triggered by deep-level defects and poor crystallization quality increase environmental risk and become a critical challenge for eco-friendly PSCs. Here, a novel 2D polyoxometalate (POM)-based metal-organic framework (MOF) (C₅ NH₅ )₄ (C₃ N₂ H₅ )₂ Zn₃ (H₈ P₄ Mo₆ O₃₁ )₂ ·2H₂ O (POMOF) is ingeniously devised to address these issues. Note that the integration of POM endows POMOF with great advantages of electrical conductivity and charge mobility. Ordered POMOF induces the crystallization of high-quality perovskite film and eliminates lead-based defects to improve internal stability. The resultant PSCs achieve a superior power conversion efficiency (23.3%) accompanied by improved stability that maintains ≈90% of its original efficiency after 1600 h. Meanwhile, POMOF with phosphate groups effectively prevents lead leakage through in situ chemical anchoring and adsorption methods to reduce environmental risk. This work provides an effective strategy to minimize lead-based defects and leakage in sustainable PSCs through multi-functional POM-based MOF material.

Lead immobilization for environmentally sustainable perovskite solar cells

Lead halide perovskites are promising semiconducting materials for solar energy harvesting. However, the presence of heavy-metal lead ions is problematic when considering potential harmful leakage into the environment from broken cells and also from a public acceptance point of view. Moreover, strict legislation on the use of lead around the world has driven innovation in the development of strategies for recycling end-of-life products by means of environmentally friendly and cost-effective routes. Lead immobilization is a strategy to transform water-soluble lead ions into insoluble, nonbioavailable and nontransportable forms over large pH and temperature ranges and to suppress lead leakage if the devices are damaged. An ideal methodology should ensure sufficient lead-chelating capability without substantially influencing the device performance, production cost and recycling. Here we analyse chemical approaches to immobilize Pb2+ from perovskite solar cells, such as grain isolation, lead complexation, structure integration and adsorption of leaked lead, based on their feasibility to suppress lead leakage to a minimal level. We highlight the need for a standard lead-leakage test and related mathematical model to be established for the reliable evaluation of the potential environmental risk of perovskite optoelectronics.

Fate and Exposure Assessment of Pb Leachate from Hypothetical Breakage Events of Perovskite Photovoltaic Modules

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.

Lead Sequestration in Perovskite Photovoltaic Device Encapsulated with Water-Proof and Adhesive Poly(ionic liquid)

The inevitable usage of toxic lead impedes the commercialization of lead halide perovskite solar cells, especially considering lead ions potentially unseals from the discarded and damaged devices and consequently contaminates the environment. In this work, we proposed a poly(ionic liquid) (PIL) cohered sandwich structure (PCSS) to realize lead sequestration in perovskite solar cells by a water-proof and adhesive poly([1-(3-propionic acid)-3-vinylimidazolium] bis(trifluoromethanesulphonyl)imide (PPVI-TFSI). A transparent ambidextrous protective shield manufactured from PPVI-TFSI was achieved and applied in lead sequestration for perovskite solar cells. PCSS provides robustness and water-resistance, which improves device stability toward water erosion and extreme situations (such as acid, base, salty water, and hot water). PPVI-TFSI exhibited excellent affinity toward lead with adsorption capacity of 516 mg·g^-1, which assisted to prevent lead leakage in abandoned devices as proved in the test of wheat germination vividly. PCSS provides a promising solution for complex lead sequestration and management issues, which contribute to the commercialization of perovskite solar cells.

Organolead Halide-Based Coordination Polymers: Intrinsic Stability and Photophysical Applications

ConspectusOrganolead halide-based photovoltaics are one of the state-of-the-art solar cell systems with efficiencies increasing to 25% over the past decade, ascribed to their high light-absorption coefficient, broad wavelength coverage, tunable band structure, and excellent carrier mobility. Indeed, these optical characteristics are highly demanding in photocatalysis and photoluminescence (PL), which also involve the solar energy utilization and charge transport. However, the vast majority of organolead halides are ionically bonded structures and susceptible to degradation upon high-polarity protic molecules (e.g., water (vapor) and alcohol), which are often inevitable in many photochemical applications. Encapsulation is a commonly used stabilization approach by coating protective layers, avoiding the direct contact between organolead halides and polar molecules. However, this may partially hinder the light penetration to the inner hybrid halide materials, and introduce new interface problems that are important in photocatalysis and luminescent sensing. Therefore, developing intrinsically stable organometal halide hybrids is a major target for their applications in optoelectronic applications.In this Account, recent research progress on the synthesis of organolead halide-based coordination polymers for a variety of photoactive applications is described. Herein, we propose a general strategy to advance the intrinsic stability of organometal halide crystalline materials by using coordinating anionic organic linkers, which occupy the excellent photophysical features analogous to those of perovskites. Unlike the organoammonium cations as for ionically bonded structures, the anionic structure-directing agents (e.g., organocarboxylates) render well-defined metal-carboxylate coordination motifs in extended architectures spanning from low-dimensional (0D, 1D) to high-dimensional cationic inorganic Pb-X-Pb (X = F^-/Cl^-/Br^-/I^-) sublattices. This family of organolead halide coordination polymers can endure chemically reactive environments over a wide range of pH and aqueous boiling condition, which have been systematically investigated by experimental studies and theoretical calculations. Many chloride/bromide-based coordination polymers show air-stable, broadband self-trapped emission with large Stokes shift and high color rendition, exhibiting the absolute quantum yields of 35-72%. Among them, the porous frameworks with low-dimensional (0D, 1D) inorganic blocks are recognized as a rare class of porous metal-organic frameworks (MOFs) constructed by lead halides as secondary building units (SBUs). They not only occupy substantially higher light-harvesting and carrier-transport properties than conventional metal oxide-based MOFs, but also allow for isoreticular modification to regulate the PL characteristics by guest molecules. More importantly, combining the high stability with excellent carrier characteristics, a layered organolead iodide coordination polymer shows the overall photocatalytic water splitting without the use of any sacrificial agent under simulated sunlight illumination. Given the wide choice of structurally diverse organocarboxylate linkers, we hope this Account provides deep insights on the importance of coordination chemistry in the discovery of a wide family of intrinsically stable organolead halides to expand their photophysical applications.

Environmental impact of metal halide perovskite solar cells and potential mitigation strategies: A critical review

Metal halide perovskite solar cells (PSCs) have gained extensive attention in the field of solar photovoltaic technology over the past few years. Despite being a remarkable alternative to fossil fuels, solar cells may have detrimental effects on the environment and human health owing to the use of toxic materials during manufacturing. Although modern metal-halide-based PSCs are stable and have encapsulation to prevent the release of potentially toxic materials into the environment, their destruction due to strong winds, hail, snow, landslides, fires, or waste disposal can result in the exposure of these materials to the environment. This may lead to the contamination of soil and groundwater, and uptake of potentially toxic elements by plants, subsequently affecting humans and other living organisms via food chain contamination. Despite worldwide concern, the environmental and ecotoxicological impacts of metal-halide-based PSCs have not been comprehensively surveyed. This review summarizes and critically evaluates the current status of metal-halide-based PSC production and its impact on environmental sustainability, food security, and human health. Furthermore, safe handling and disposal methods for the waste generated from metal-halide-based PSCs are proposed, with a focus on recycling and reuse. Although some studies have suggested that the amount of lead released from metal halide PSCs is far below the maximum permissible levels in most soils, a clear conclusion cannot be reached until real contamination scenarios are assessed under field conditions. Precautions must be taken to minimize environmental contamination throughout the lifecycle of PSCs until nontoxic and similarly performing alternative solar photovoltaic products are developed.

Halide Chemistry in Tin Perovskite Optoelectronics: Bottlenecks and Opportunities

Tin halide perovskites (Sn HaPs) are the top lead-free choice for perovskite optoelectronics, but the oxidation of perovskite Sn2+ to Sn4+ remains a key challenge. However, the role of inconspicuous chemical processes remains underexplored. Specifically, the halide component in Sn HaPs (typically iodide) has been shown to play a key role in dictating device performance and stability due to its high reactivity. Here we describe the impact of native halide chemistry on Sn HaPs. Specifically, molecular halogen formation in Sn HaPs and its influence on degradation is reviewed, emphasising the benefits of iodide substitution for improving stability. Next, the ecological impact of halide products of Sn HaP degradation and its mitigation are considered. The development of visible Sn HaP emitters via halide tuning is also summarised. Lastly, halide defect management and interfacial engineering for Sn HaP devices are discussed. These insights will inspire efficient and robust Sn HaP optoelectronics.

Synergistic Effect of Surface p-Doping and Passivation Improves the Efficiency, Stability, and Reduces Lead Leakage in All-Inorganic CsPbIBr2 -Based Perovskite Solar Cells

Wide-bandgap inorganic cesium lead halide CsPbIBr₂ is a popular optoelectronic material that researchers are interested in because of the character that balances the power conversion efficiency and stability of solar cells. It also has great potential in semitransparent solar cells, indoor photovoltaics, and as a subcell for tandem solar cells. Although CsPbIBr₂ -based devices have achieved good performance, the open-circuit voltage (V_oc ) of CsPbIBr₂ -based perovskite solar cells (PSCs) is still lower, and it is critical to further reduce large energy losses (E_loss ). Herein, a strategy is proposed for achieving surface p-type doping for CsPbIBr₂ -based perovskite for the first time, using 1,5-Diaminopentane dihydroiodide at the perovskite surface to improve hole extraction efficiency. Meanwhile, the adjusted energy levels reduce E_loss and improve V_oc of the CsPbIBr₂ PSCs. Furthermore, the Cs- and Br-vacancies at the interface are filled, reducing structural disorder and defect states and thus improving the quality of the perovskite film. As a result, the target device achieves a high efficiency of 11.02% with a V_oc of 1.33 V, which is among the best values. In addition to the improved performance, the stability of the target device under various conditions is enhanced, and the lead leakage is effectively suppressed.

Environmental and health risks of perovskite solar modules: Case for better test standards and risk mitigation solutions

Perovskite solar cells (PSCs) promise high efficiencies and low manufacturing costs. Most formulations, however, contain lead, which raises health and environmental concerns. In this review, we use a risk assessment approach to identify and evaluate the technology risks to the environment and human health. We analyze the risks by following the technology from production to transportation to installation to disposal and examine existing environmental and safety regulations in each context. We review published data from leaching and air emissions testing and highlight gaps in current knowledge and a need for more standardization. Methods to avoid lead release through introduction of absorbing materials or use of alternative PSC formulations are reviewed. We conclude with the recommendation to develop recycling programs for PSCs and further standardized testing to understand risks related to leaching and fires.

Remarkable Stability and Optoelectronic Properties of an All-Inorganic CsSn0.5Ge0.5I3 Perovskite Solar Cell

Sn-Ge mixed perovskites have been proposed as promising lead-free candidates in the photovoltaics (PV) field. In this work, we discovered a stable P1 phase Sn-Ge mixed structure (CsSn_0.5Ge_0.5I₃) with an appropriate band gap value of 1.19 eV, which manifests its unique structural stability and physics properties. The thermodynamic stability of this mixed structure under different growth conditions and all possible native defects are depicted in detail. The formation energies and dominant native point defects indicate that P1 phase CsSn_0.5Ge_0.5I₃ exhibits unipolar self-doping behavior (p-type conductivity) and good defect tolerance while the growth condition changes. In addition, the calculation of light absorption confirmed that the P1 phase has a higher light absorption coefficient than that of MAPbI₃ in the visible light range, showing excellent light absorption. Our work not only provides theoretical guidance for unraveling the unusual structural stability of Sn-Ge mixed perovskites, but also offers a useful scheme to modulate the stability and optoelectronic properties of Ge-based perovskites through alloy engineering.

Atomistic Description of the Impact of Spacer Selection on Two-Dimensional (2D) Perovskites: A Case Study of 2D Ruddlesden-Popper CsPbI3 Analogues

Inorganic CsPbI₃ perovskites have become desirable for use in photovoltaic devices due to their excellent optoelectronic properties and increased resilience to thermal degradation compared to organic-inorganic perovskites. An effective strategy for improving both the performance and the phase stability of CsPbI₃-based perovskites is through introducing a diverse set of spacing cations separating inorganic layers in their two-dimensional (2D) analogues. In this work, CsPbI₃-based 2D Ruddlesden-Popper perovskites were investigated using three aromatic spacers, 2-thiophenemethylamine (ThMA), 2-thiopheneformamidine (ThFA), and benzylammonium, fluorinated through para substitution (pFBA). Our findings highlight the importance of the local bonding environment between organic spacers and the PbI₆ octahedra. Additionally, we demonstrated the importance of energetic alignment between electronic states on spacing cations and inorganic layers for optoelectronic applications. Furthermore, thermoelectric performance was investigated revealing a preference for p-type ThFA and n-type ThMA and pFBA configurations.

Enabling water-free PEDOT as hole selective layer in lead-free tin perovskite solar cells

Metal halide perovskites are set to revolutionise photovoltaic energy harvesting owing to an unmatched combination of high efficiency and low fabrication costs. However, to improve the sustainability of this technology, replacing lead with less toxic tin is highly desired. Tin halide perovskites are approaching 15% in power conversion efficiency (PCE), mainly employing PEDOT:PSS as a hole-selective layer. Unfortunately, PEDOT:PSS is processed from an aqueous solution, which is hardly compatible with the strict anoxic requirements for processing tin halide perovskites due to tin's instability to oxidation. Here, we present a water-free PEDOT formulation for developing tin-based lead-free perovskite solar cells. We show that the main difference between the PCE of devices made from aqueous and water-free PEDOT is due to the marked hydrophobicity of the latter, which complicates the perovskite deposition. By modifying the surface of water-free PEDOT with a thin Al2O3 interlayer, we could achieve good perovskite morphology that enabled perovskite solar cells with a PCE of 7.5%.

Lead-binding biogenic polyelectrolyte multilayer coating for lead retention in perovskite solar cells

Perovskite solar cells promise to deliver high efficiencies at low manufacturing costs. Yet on their way towards commercialization, they have to face the associated risk of potential lead leakage into the environment after damage to the cell's encapsulation. Here we present a new approach to generate a lead binding coating, based on a layer-by-layer deposition of biopolymers. A lead-adsorbing functionality was shown after subsequent crosslinking, demonstrating a high binding capacity. The lead binding capabilities could be further enhanced by increasing the thickness of the coatings, analyzed both in the supernatant and on the surface of the coated material. The thin-layered coating had a thickness of less than one micrometer, was stable even under low pH conditions and could successfully be transferred onto different substrates, ranging from silicon, gold and glass substrates to polymeric nonwoven materials with high surface areas, further increasing its lead binding capacity. This newly described coating was applied within perovskite solar cell stacks without impeding the overall efficiency but strongly reducing the amount of lead released after simulated rain tests on devices with damaged encapsulation. Accordingly, incorporation of lead-binding polyelectrolyte multilayers inside the encapsulation of perovskite solar cells shows great potential to limit the perovskite solar cells inherent risk of lead leakage in a sustainable manner.

Improved Energy Transfer in Mn-Doped Cs3Cu2I5 Microcrystals Induced by Localized Lattice Distortion

With nontoxicity and high emission efficiency, luminescent copper(I)-based halides have attracted much attention as alternatives for lead-based perovskites in photoelectric domains. However, extending the emission wavelength by doping with Mn²⁺ in a facile way is still a challenge. In this work, Mn²⁺-doped Cs₃Cu₂I₅ microcrystals were synthesized by a mild solution method, and double emission bands from self-trapped excitons (STEs) and Mn²⁺ peaking at 445 and 560 nm, respectively, were observed. More importantly, further introduction of alkali metal ions (Rb⁺, K⁺, Na⁺) considerably promoted the luminescence performance of the Cs₃Cu₂I₅-Mn microcrystals. The STE → Mn²⁺ energy transfer efficiency of the typical sample doped with Na⁺ increased from ∼0 to 21.30%, and the photoluminescence quantum yield (PLQY) increased from 47.32% to 62.06%. The detailed structural and optical characterizations combined with DFT calculations proved that the doping with alkali metal ions causes lattice distortion and enhances the coupling between [MnI₄] and [CuI₄] tetrahedra, thus promoting the energy transfer efficiency and the PLQY.

D-π-A-Type Pyrazolo[1,5-a]pyrimidine-Based Hole-Transporting Materials for Perovskite Solar Cells: Effect of the Functionalization Position

Donor−acceptor (D−A) small molecules are regarded as promising hole-transporting materials for perovskite solar cells (PSCs) due to their tunable optoelectronic properties. This paper reports the design, synthesis and characterization of three novel isomeric D-π-A small molecules PY1, PY2 and PY3. The chemical structures of the molecules consist of a pyrazolo[1,5-a]pyrimidine acceptor core functionalized with one 3,6-bis(4,4′-dimethoxydiphenylamino)carbazole (3,6-CzDMPA) donor moiety via a phenyl π-spacer at the 3, 5 and 7 positions, respectively. The isolated compounds possess suitable energy levels, sufficient thermal stability (Td > 400 °C), molecular glass behavior with Tg values in the range of 127−136 °C slightly higher than that of the reference material Spiro-OMeTAD (126 °C) and acceptable hydrophobicity. Undoped PY1 demonstrates the highest hole mobility (3 × 10−6 cm2 V−1 s−1) compared to PY2 and PY3 (1.3 × 10−6 cm2 V−1 s−1). The whole isomers were incorporated as doped HTMs in planar n-i-p PSCs based on double cation perovskite FA0.85Cs0.15Pb(I0.85Br0.15)3. The non-optimized device fabricated using PY1 exhibited a power conversion efficiency (PCE) of 12.41%, similar to that obtained using the reference, Spiro-OMeTAD, which demonstrated a maximum PCE of 12.58% under the same conditions. The PY2 and PY3 materials demonstrated slightly lower performance in device configuration, with relatively moderate PCEs of 10.21% and 10.82%, respectively, and slight hysteresis behavior (−0.01 and 0.02). The preliminary stability testing of PSCs is also described. The PY1-based device exhibited better stability than the device using Spiro-OMeTAD, which could be related to its slightly superior hydrophobic character preventing water diffusion into the perovskite layer.

Radix Astragali residue-derived porous amino-laced double-network hydrogel for efficient Pb(II) removal: Performance and modeling

Valorizing solid waste for heavy metal adsorption is highly desirable to avoid global natural resources depletion. In this study, we developed a new protocol to valorize Radix Astragali residue (one of the Chinese medicine residues) into a low-cost, chemically robust, and highly permeable (ca. 90%) amino-laced porous double-network hydrogel (NH₂-CNFs/PAA) for efficient Pb(II) adsorption. The NH₂-CNFs/PAA showed (i) excellent Pb(II) adsorption capacity (i.e., 994.5 mg g^-1, ~4.8 mmol g^-1), (ii) fast adsorption kinetics (k_f = 2.01 ×10^-5 m s^-1), (iii) broad working pH range (2.0-6.0), and (iv) excellent regeneration capability (~15 cycles). (v) excellent performance in various real water matrices on Pb(II) removal. Moreover, its high selectivity (distribution coefficient K_d ~2.4 ×10⁶ mL g^-1) toward Pb(II) was owing to the present of abundant amino groups (-NH₂). Furthermore, the fix-bed column test indicated the NH₂-CNFs/PAA can effectively remove 114.6 bed volumes (influent concentration ~5000 μg L^-1) with an enrichment factor 10.9. The full-scale system modeling (i.e., pore surface diffusion model (PSDM)) has been applied to predict the NH₂-CNFs/PAA performance on Pb(II) removal. Overall, we have provided an alternative "win-win" scenario that can resolve the Chinese medicine residues disposal issue by valorizing it into high performance gel-based adsorbents for efficient heavy metal removal.

Lead Industry Influence in the 21st Century: An Old Playbook for a "Modern Metal"

In recent years, lead poisoning has received increasing attention as lead production continues to grow and the industry shifts the most polluting processes (e.g., smelting ore and recycling batteries) to low- and middle-income countries. The hazards associated with lead exposures have been well known for centuries while the industry actively promoted lead products. Less well known is how the industry continues to promote the "safe and responsible" use of lead and support research to question the underlying science and avoid regulation. Here I explore the historical context for recent actions that the industry has taken to ensure its longevity. Lead industry associations continue to employ some of the same themes that have proven successful in the past. Efforts to forestall regulatory initiatives to reduce emissions and restrict lead applications continue. Large battery manufacturers and recyclers and their associations place blame on informal-sector recycling to draw focus away from their own emissions. They have sought the cooperation of hired scientific experts and have funded United Nations organizations and nongovernmental organizations to deflect attention from their own contributions to global lead poisoning. (Am J Public Health. 2022;112(S7):S723-S729. https://doi.org/10.2105/AJPH.2022.306960).

Lead Sequestration from Halide Perovskite Solar Cells with a Low-Cost Thiol-Containing Encapsulant

Perovskite solar cells (PSCs) are being studied and developed because of the outstanding properties of halide perovskites as photovoltaic materials and high conversion efficiencies achieved with the best PSCs. However, leaching out of lead (Pb) ions into the environment presents potential public health risks. We show that thiol-functionalized nanoparticles provide an economic way of minimizing Pb leaching in the case of PSC module damage and subsequent water exposure (at most, ∼2.5% of today's crystal silicon solar panel production cost per square meter). Using commercial materials and methods, we retain ∼90% of Pb without degrading the photovoltaic performance of the cells, compared with nonencapsulated devices, yielding a worst-case scenario of top-soil pollution below natural Pb levels and well below the U.S. Environmental Protection Agency limits.

Avoiding Structural Collapse to Reduce Lead Leakage in Perovskite Photovoltaics

Perovskite solar cells (PSCs) have become a promising candidate for the next-generation photovoltaic technologies. As an essential element for high-efficiency PSCs however, the heavy metal Pb is soluble in water, causing a serious threat to the environment and human health. Due to the weak ionic bonding in three-dimensional (3D) perovskites, drastic structure decomposition occurs when immersing the perovskite film in water, which accelerates the Pb leakage. By introducing the chemically stable Dion-Jacobson (DJ) 2D perovskite at the 3D perovskite surface, the film dissolution is significantly slowed down, which retards lead leakage. As a result, the Pb contamination is dramatically reduced under various extreme conditions. In addition, the PSCs device deliver a power conversion efficiency (PCE) of 23.6 % and retain over 95 % of their initial PCE after the maximum power point tracking for over 1100 h.

Halide Perovskite Solar Cells for Building Integrated Photovoltaics: Transforming Building Façades into Power Generators

The rapid emergence of organic-inorganic lead halide perovskites for low-cost and high-efficiency photovoltaics promises to impact new photovoltaic concepts. Their high power conversion efficiencies, ability to coat perovskite layers on glass via various scalable deposition techniques, excellent optoelectronic properties, and synthetic versatility for modulating transparency and color allow perovskite solar cells (PSCs) to be an ideal solution for building-integrated photovoltaics (BIPVs), which transforms windows or façades into electric power generators. In this review, the unique features and properties of PSCs for BIPV application are accessed. Device engineering and optical management strategies of active layers, interlayers, and electrodes for semitransparent, bifacial, and colorful PSCs are also discussed. The performance of PSCs under conditions that are relevant for BIPV such as different operational temperature, light intensity, and light incident angle are also reviewed. Recent outdoor stability testing of PSCs in different countries and other demonstration of scalability and deployment of PSCs are also spotlighted. Finally, the current challenges and future opportunities for realizing perovskite-based BIPV are discussed.

Degradation and Self-Healing in Perovskite Solar Cells

Organic-inorganic halide perovskites are well-known for their unique self-healing ability. In the presence of strong external stimuli, such as light, temperature, and moisture, high-energy defects are created which can be healed by removing the perovskite from the degradation source. This self-healing ability has been showcased in devices with recoverable performance and day-and-night cycling operation to dramatically extend the device lifetime and even mechanical durability. However, to date, the mechanistic details and theory around this captivating trait are sparse and convoluted by the complex nature of perovskites. With a clear understanding of the intrinsic self-healing property, perovskite solar cells with extended lifetimes and durability can be designed to realize the large-scale commercialization of perovskite solar cells. Here, we spotlight the relevant degradation and self-healing literature and then propose design strategies to help conceptualize future research.

Friction-Dominated Carrier Excitation and Transport Mechanism for GaN-Based Direct-Current Triboelectric Nanogenerators

The semiconductor triboelectric nanogenerator (TENG) based on the tribovoltaic effect has the characteristics of direct current and high current density, but the energy transfer and conversion mechanism is not completely clear. Here, a series of gallium nitride (GaN)-based semiconductor direct-current TENGs (SDC-TENGs) are investigated for clarifying the carrier excitation and transport mechanism. During the friction process, the external output current always flows from GaN to silicon or aluminum, regardless of the direction of the built-in electric field, because of the semiconductor types. These results reveal that the carrier transport direction is dominated by the interfacial electric field formed by triboelectrification, which is also verified under different bias voltages. Moreover, the characteristics dependent on the frictional force have been systematically investigated under different normal forces and frictional modes. The open-circuit voltage and short-circuit current of SDC-TENG are both increased with a larger frictional force, which shows that the more severe friction results in both a larger interface electric field and more excited carriers. The maximum voltage can reach 25 V for lighting up a series of LEDs, which is enhanced by four times compared to the cutting-edge reported SDC-TENGs. This work has clarified the friction-dominated carrier excitation and transport mechanism for the tribovoltaic effect, which demonstrates the great potential of semiconductor materials for frictional energy recovery and utilization.

Quantifying Efficiency Limitations in All-Inorganic Halide Perovskite Solar Cells

While halide perovskites have excellent optoelectronic properties, their poor stability is a major obstacle toward commercialization. There is a strong interest to move away from organic A-site cations such as methylammonium and formamidinium toward Cs with the aim of improving thermal stability of the perovskite layers. While the optoelectronic properties and the device performance of Cs-based all-inorganic lead-halide perovskites are very good, they are still trailing behind those of perovskites that use organic cations. Here, the state-of-the-art of all-inorganic perovskites for photovoltaic applications is reviewed by performing detailed meta-analyses of key performance parameters on the cell and material level. Key material properties such as carrier mobilities, external photoluminescence quantum efficiency, and photoluminescence lifetime are discussed and what is known about defect tolerance in all-inorganic is compared relative to hybrid (organic-inorganic) perovskites. Subsequently, a unified approach is adopted for analyzing performance losses in perovskite solar cells based on breaking down the losses into several figures of merit representing recombination losses, resistive losses, and optical losses. Based on this detailed loss analysis, guidelines are eventually developed for future performance improvement of all-inorganic perovskite solar cells.

Potential lead toxicity and leakage issues on lead halide perovskite photovoltaics

Recently, lead halide perovskite solar cells have become a promising next-generation photovoltaics candidate for large-scale application to realize low-cost renewable electricity generation. Although perovskite solar cells have tremendous advantages such as high photovoltaic performance, low cost and facile solution-based fabrication, the issues involving lead could be one of the main obstacles for its commercialization and large-scale applications. Lead has been widely used in photovoltaics industry, yielding its environmental and health issues of vital importance because of the widespread application of photovoltaics. When the solar cell panels especially perovskite solar cells are damaged, lead would possibly leak into the surrounding environment, causing air, soil and groundwater contamination. Therefore, lots of research efforts have been put into evaluating the lead toxicity and potential leakage issues, as well as studying the encapsulation of lead to deal with leakage issue during fire hazard and precipitation in photovoltaics. In this review, we summarize the latest progress on investigating the lead safety issue on photovoltaics, especially lead halide perovskite solar cells, and the corresponding solutions. We also outlook the future development towards solving the lead safety issues from different aspects.

Dual Functions of Performance Improvement and Lead Leakage Mitigation of Perovskite Solar Cells Enabled by Phenylbenzimidazole Sulfonic Acid

With the continuous improvement of performance of lead-based perovskite solar cells (PSCs), the potential harm of water-soluble lead ion (Pb²⁺ ) to environment and public health is emerging as a major obstacle to their commercialization. Herein, an amphoteric phenylbenzimidazole sulfonic acid (PBSA) that is almost insoluble in water is added to the perovskite precursor to simultaneously regulate crystallization growth, passivate defects, and mitigate lead leakage of high-performance PSCs. Through systematic research, it is found that PBSA can not only regulate the crystallization of perovskite grains to form the film, but also passivate the defects of annealed films mainly due to the strong interaction between the functional groups in PBSA and Pb²⁺ , which greatly improves the crystallinity and stability of perovskite films. Consequently, the highest power conversion efficiency of 23.27% is achieved in 0.09 cm² devices and 15.31% is obtained for large-area modules with an aperture area of 19.32 cm² , along with negligible hysteresis and improved stability. Moreover, the leakage of lead ions from unpackaged devices is effectively prevented owing to the strong coupling between PBSA molecules and water-soluble Pb²⁺ to form insoluble complexes in water, which is of great significance to promote the application of optoelectronic devices based on lead-based perovskite materials.