Avoiding Structural Collapse to Reduce Lead Leakage in Perovskite Photovoltaics

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.

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.

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.

Exploiting halide perovskites for heavy metal ion detection

Heavy metal ions such as mercury (Hg), copper (Cu), and cadmium (Cd) pose significant threats to ecosystems and human health due to their toxicity and bioaccumulation potential. With growing environmental concerns over heavy metal ion pollution, there is an urgent need to develop efficient detection methods for safeguarding public health and the environment. Various materials, including polymers, nanomaterials, and porous substances, have been used for heavy metal ion detection and have shown promising performance for different scenarios. However, each of these materials has certain limitations as probes. Metal halide perovskites (MHPs), known for their exceptional optoelectronic properties and high structural and chemical tunability, have gained great attention in applications such as photovoltaics and LEDs. Yet, their potential as metal ion probes remains rarely explored. This review assesses MHPs as prospective materials for heavy metal ion detection, taking their structure, chemical properties, and responses to external stimuli into consideration. Three key detection mechanisms-cation exchange (CE), electron transfer (ET), and fluorescence resonance energy transfer (FRET), are explored to understand how metal ions trigger fluorescence changes on perovskites, enabling their detection. Finally, current avenues of developing perovskite probes are discussed, which include exploration of lead-free perovskites to mitigate environmental concerns arising from lead leakage and the pursuit of achieving high-sensitivity and stable detection in aqueous media, summarizing the existing and promising strategies in this field.

Cesium Cyclopropane Acid-Aided Crystal Growth Enables Efficient Inorganic Perovskite Solar Cells with a High Moisture Tolerance

While all-inorganic halide perovskites (iHPs) are promising photovoltaic materials, the associated water sensitivity of iHPs calls for stringent humidity control to reach satisfactory photovoltaic efficiencies. Herein, we report a moisture-insensitive perovskite formation route under ambient air for CsPbI2 Br-based iHPs via cesium cyclopropane acids (C3 ) as a compound introducer. With this approach, appreciably enhanced crystallization quality and moisture tolerance of CsPbI2 Br are attained. The improvements are attributed to the modified evaporation enthalpy of the volatile side product of DMA-acid initiated by Cs-acids. As such, the water-involving reaction is directed toward the DMA-acids, leaving the target CsPbI2 Br perovskites insensitive to ambient humidity. We highlight that by controlling the C3 concentration, the dependence of power conversion efficiency (PCE) in CsPbI2 Br devices on the humidity level during perovskite film formation becomes favorably weakened, with the PCEs remaining relatively high (>15 %) associated with improved device stability for RH levels changed from 25 % to 65 %. The champion solar cells yield an impressive PCE exceeding 17 %, showing small degradations (<10 %) for 2000 hours of shell storage and 300 hours of 85/85 (temperature/humidity) tests. The demonstrated C3 -based strategy provides an enabler for improving the long-sought moisture-stability of iHPs toward high photovoltaic device performance.

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.

Mixed Cations Enabled Combined Bulk and Interfacial Passivation for Efficient and Stable Perovskite Solar Cells

Here, we report a mixed GAI and MAI (MGM) treatment method by forming a 2D alternating-cation-interlayer (ACI) phase (n = 2) perovskite layer on the 3D perovskite, modulating the bulk and interfacial defects in the perovskite films simultaneously, leading to the suppressed nonradiative recombination, longer lifetime, higher mobility, and reduced trap density. Consequently, the devices' performance is enhanced to 24.5% and 18.7% for 0.12 and 64 cm2, respectively. In addition, the MGM treatment can be applied to a wide range of perovskite compositions, including MA-, FA-, MAFA-, and CsFAMA-based lead halide perovskites, making it a general method for preparing efficient perovskite solar cells. Without encapsulation, the treated devices show improved stabilities.

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.