Efficiencies of lead halide perovskite photovoltaics (LHP PVs) have increased to over 26%, and over 30% for tandems, and potential for low manufacturing costs puts them on track for near-future commercialization.  While most efforts to date have focused on stability and scalability of LHP PVs, the environmental impact of their manufacturing should be considered, and concern regarding the toxicity of lead (Pb) remains a major challenge to large-scale commercialization. This invited talk will describe two recent studies related to (1) life cycle assessment of cation precursors, and (2) fate of toxic Pb leachate from hypothetical breakage of fielded module arrays.

Devices exhibiting the best combination of high efficiency and long operational lifetimes have used mixed cation perovskite absorber layers such as cesium / methylammonium / formamidinium lead iodide (Cs_x­MA_yFA_1-x-yPbI₃). However, the associated environmental burdens of the supply chains of perovskite precursors should also be considered when selecting compositions for commercialization.  Prior literature based on laboratory-scale data reported a particularly high environmental burden for FA and warned against using these highest-performing film compositions.  Here we used updated data sources, process scale-up concepts, and sensitivity analysis to build commercial-scale life cycle inventory (LCI) models for perovskite precursors. Our life cycle assessment results indicate that the environmental burdens of CsI, MAI, and FAI are similar to each other. This conclusion reveals that the composition can be selected based on PV efficiency and operational stability, without additional constraints of environmental impact. The current cesium supply appears sufficient for near-future perovskite deployment. Our commercial-scale LCI models for perovskite films aid in more transparent and robust environmental analysis that can contribute to industrial manufacturing choices.

Second, we will 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 US 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.

The shift to renewable energy sources is essential for achieving global sustainability and reducing carbon emissions. Solar energy, alongside wind power, plays a central role in this transition, with annual photovoltaic production projected to exceed 1 terawatt peak (TWP) by 2025. However, the exponential growth in solar panel deployment brings critical challenges regarding end-of-life management. Sustainable recycling strategies are urgently needed to minimize environmental impact and ensure the efficient recovery of valuable materials. Embracing a circular recycling model not only mitigates the risks of landfilling but also supports resource conservation and the long-term sustainability of solar technologies.

Perovskite solar cells (PSCs), a next-generation photovoltaic technology, offer tremendous potential due to their high efficiency, low material costs, and scalability. Yet, the sustainability of PSCs depends on overcoming significant recycling and environmental hurdles, particularly the safe recovery and reuse of lead halides. Our research addresses these challenges by focusing on the circular recovery of materials, developing scalable processes that minimize waste and enable the reintegration of critical resources into the production cycle.

In the context of closed-loop recycling, we demonstrated a novel solvent-based layer-by-layer extraction process that enables the recovery of MAPbI₃ perovskite solar cells with a 99.97% mass recovery rate. Essential components such as ITO glass, SnO₂, MAPbI₃, and spiro-OMeTAD were successfully purified and reused. Solar devices fabricated using recycled materials retained performance comparable to those produced with virgin components, achieving efficiencies of 19%. A techno-economic analysis revealed that adopting this recycling strategy could reduce material costs by 63.7% at the laboratory scale, highlighting its cost-effectiveness and potential for broader adoption.

To address the environmental concerns associated with lead waste, we developed an innovative recycling process to convert contaminated lead into high-purity lead iodide (PbI₂). This method achieves near-complete conversion with a Faradaic efficiency close to unity. Single-crystal growth purification resulted in PbI₂ of 35% purity, with residual materials fed back into the recycling loop. The process demonstrated a scalable output of approximately 1g per hour, with clear pathways for industrial upscaling. Fabricating perovskite solar cells from the recovered PbI₂ resulted in efficiencies exceeding 20%, confirming the viability of repurposing lead waste for sustainable photovoltaic production.

By transforming legacy lead waste from industrial and household sources into high-value materials for new solar cells, our work provides a scalable and environmentally responsible solution to lead recycling. This approach not only eliminates ecological hazards but also advances a circular economy, where resource efficiency and waste minimization drive the sustainability of perovskite solar technologies.

Tackling the global energy crisis demands the seamless integration of energy harvesting, conversion, and storage systems into a unified module. Such systems mitigate the inconsistencies of renewable energy sources, making them ideal for portable optoelectronic devices operating in both outdoor and indoor lighting conditions. [1-2] In this study, we present an innovative approach by integrating a carbon perovskite solar cell (CPSC) with an MXene-based in-plane microsupercapacitor (MSC) on a single substrate. The three-terminal device, constructed on a glass/indium tin oxide (glass/ITO) substrate, features a shared terminal between the MSC and the solar cell, alongside two dedicated terminals for individual components. The MXene-based MSC was developed using blade-coating of water-processed Ti₃C₂Tₓ MXene ink onto the substrate, followed by laser scribing to form an interdigitated in-plane structure. This MSC achieved a capacitance of 16 mF/cm² at a current density of 0.08 mA/cm² and exhibited impressive durability, retaining 86% of its capacitance and delivering a coulombic efficiency of 96% after 6,000 charge-discharge cycles. The photovoltaic component demonstrated a conversion efficiency of 7.11% under standard sunlight conditions (1 sun) and 22.6% under indoor lighting at 1000 lx. The integrated device showcased exceptional performance across varying light environments, achieving an overall efficiency of 3.8% and a storage efficiency of 59.1%. This breakthrough photosupercapacitor represents a significant step forward for portable optoelectronic devices, paving the way for advanced solutions in energy storage and conversion technologies.

Halide perovskites have gained a lot of attention in energy storage applications due to their high electrical and ionic conductivity, large diffusion coefficients and ease of structural dimensions. However, the use of toxic solvents and lead in the synthesis processes has limited their potential for commercial development [1]. To overcome these challenges, we developed the mechanosynthesis of lead-free 2D and 3D perovskite powders for supercapacitor applications. Using this scalable and solvent-free ball-milling technique, we have synthesized methylammonium copper bromide (MA₂CuBr₄), cesium bismuth chloride (Cs₂Bi₃Cl₉) perovskites, and MA₂CuBr₄-graphite composite powders which were composed of aggregates of nanograins. After mechanosynthesis, MA₂CuBr₄ powders were washed and centrifuged in methyl acetate several times to obtain the orthorhombic crystal structure (with Pbca space group) and confirmed by the x-ray diffraction analysis [2]. MA₂CuBr₄ was first studied as an electrode material for supercapacitor and we have tested two electrolytes/working electrode systems. In the optimized LiPF₆ electrolyte/Ti electrode system, MA₂CuBr₄ showed stable and high average specific capacitance of 205 Fards/gram (Fg^-1) for 20 cycles as a working electrode thanks to the 2D layered morphology suitable for lithium intercalation. To the best of our knowledge, the performance of MA₂CuBr₄ perovskite was not studied for supercapacitor electrode application but is comparable to the recently reported lead-free bismuth-based perovskite (Cs₃Bi₂I₉) supercapacitor with a specific capacitance of ~242 Fg^-1 [3]. A maximum current of up to 20 miliamperes (mA) was observed at voltage of 1.72 V during the large operating voltage range of 0.3 V to 3.2 V. Witnessing the high performance of MA₂CuBr₄ as a supercapacitor, perovskite-graphite composites were synthesized using one-pot and two-pot schemes. In graphite-based composite powders, the graphite few layers were observed to distribute homogeneously within powders, indicating strong graphite-perovskite interaction. The effect of graphite addition was also studied for improving the electrochemical performance. These results demonstrated at first the great potential of mechanosynthesis, which is a green and easy-scalable powder synthesis technique to develop electrode materials for supercapacitors. This was confirmed by further experiments with another mechanosynthesized perovskite, Cs₂Bi₃Cl₉. The cyclovoltametric and charge/discharge experiments with Cs₂Bi₃Cl_9, MA₂CuBr_4, and MA₂CuBr₄-graphite composite have allowed for better evidencing the interest of such layered materials. Thus, mechanosynthesis shows a promise for creating eco-friendly, high-efficiency lead-free hybrid perovskite devices for sustainable energy storage applications.

Keywords : lead-free perovskites, green chemistry, solvent-free mechanosynthesis, electrode materials, supercapacitors, energy storage

Halide perovskite solar cells (PSCs) have rapidly approached the efficiency levels of traditional silicon photovoltaics, marking a significant breakthrough in solar technology. However, their commercial viability is compromised by their limited long-term stability. This presentation focuses on the recent strides made in enhancing the stability of PSCs through innovative interface engineering. By examining the primary factors influencing PSC stability and the mechanisms of device degradation, we have explorde how interface manipulation serves both as a corrective measure for surface defects and a defensive mechanism against environmental degradation. Special emphasis will be placed on the latest advancements in interface modification agents, interfacial regulation strategies, and the design of novel charge transport and capping layers. We aim to provide a comprehensive overview of the current challenges, recent technological advances, and future directions in the sustainability of halide perovskite photovoltaics, emphasizing the pivotal role of interface engineering in the evolution of this promising technology.

Thanks to their high absorption coefficient and ideal band-gap [1], lead halide perovskite materials are strong candidates for the next generation of solar cells, achieving certified power conversion efficiencies of over 26%. However, the development of perovskite-based solar cells is impeded by obstacles such as degradation of the perovskite layer by light, oxygen, and moisture. Addressing these challenges while advancing sustainability is critical for their widespread adoption.

Photoluminescence (PL) is a valuable tool for studying photoexcited carrier processes in solar cells. However, measuring the steady-state and time-resolved PL of perovskite thin films reveals the complex and sometimes surprising behaviors of these materials [2–4]. Here, we discuss the use of PL studies to understand the stability and performance of perovskite materials, particularly in evaluating alterations to manufacture and materials to improve sustainability. This includes the use of sustainable solvent systems and material substitutions, such as carbon electrodes as alternatives to gold. These studies are complemented by XRD and SEM analyses to investigate the effects of material and process changes on morphology, uniformity, and photovoltaic device performance.

Here, we discuss the work of the Applied Photochemistry Group at the SPECIFIC Innovation and Knowledge Centre, Swansea University, towards advancing the understanding of photostability and photochemistry of perovskite solar cells. By addressing sustainability challenges, particularly through solvent and material innovations, this research supports the transition from lab-scale to production-scale manufacture of environmentally responsible perovskite PV.

The huge expansion of nanotechnology calls for searching processes that can reduce the environmental impact of the syntheses employed to obtain nanocrystals (NCs).

In this contribution, we present the preparation of lead halide perovskites (CsPbX_3, X = Cl, Br, I) in limonene, a molecule extracted from natural sources and considered a green solvent. [1] The synthesized NCs resemble the same structural, optical and morphological properties of the homologues prepared in the common solvents, i.e. 1-octadecene. In particular, the NCs resemble cubic morphologies and possess a considerable photoluminescence quantum yield (> 80% for CsPbBr₃). Exploiting the relatively high volatility of the limonene, we verified that it can be quantitatively removed from the NCs just by vacuum pumping and demonstrated the possibility of recovering from the waste of the reactions the pure solvent that can be reused for subsequent syntheses. In addition, the substitution of 1-octadecene with limonene as the reaction solvent was analyzed by examining the consequences of the environmental impact of the entire synthesis process through a Life Cycle Assessment (LCA).

Metal-halide perovskites (MHP) are highly promising optoelectronic materials due to their exceptional properties and versatile fabrication methods [1]. These materials are crucial for solar cells and optoelectronics devices to quantum emitters.
Thermal evaporation has emerged as a pivotal method to enable precise control over film thickness, composition tuning, stress-free deposition, surface modification capabilities, and large-area [2] devices—key factors in the advancement of perovskite optoelectronics.
In this talk I will present how overcoming the challenges of scalability and reproducibility in perovskite solar cell (PSC) production, critical for their sustanaible viability. We have demonstrated the possibility of achieving a sixfold increase in speed while maintaining film quality and high-power conversion efficiencies. This accelerated co-evaporation process demonstrates the potential for large-scale, cost-effective PSC production without needing post-annealing, further simplifying the manufacturing process [3].
Moreover, leveraging on the possibility of fabricating high-quality films with high thickness control by thermal evaporation we have explored the promising field of thermally evaporated perovskite-based Multiple Quantum Wells (MQWs) [4]. MQWs structures can enhance the optoelectronic properties of nanoscale thin films, through control over electronic energy levels and quantum mechanical phenomena, and opening up avenues for unconventional optoelectronic functionalities.
We demonstrated how both thermally evaporated MAPbI3-based MQWs offer significant advancements in light-emitting and photodetection technologies, expanding their sensitivity into the near-infrared range and enhancing photoluminescence and charge separation efficiency.[5].
These recent works not only address critical challenges in scaling perovskite solar cell production but also open new avenues for optoelectronic device design, highlighting the versatility and promise of thermally evaporated perovskite materials for next-generation energy solutions.

References
1) Min, H., et al., Nature, 2021. 598, 444.; Yoo, J.J., et al., Nature, 2021. 590 587.
2) J. Li et al., Joule 2020, 4, 1035; H.A. Dewi et al., Adv. Funct. Mater. 2021, 11, 2100557; J. Li et al., Adv. Funct. Mater. 2021, 11, 2103252;
3) Dewi et al. ACS Energy Lett. 2024, 9, 4319−4322
4) Advanced Materials 2021, 33, 2005166; L. White et al. ACS Energy Lett. 2024, 9, 83;
5) L. White, ACS Energy Lett. 2024, 9, 4450.

Climate change is a race against time, and the need for more efficient and cheaper solar energy is a high priority. Perovskite-silicon tandem solar cells are among the most promising options that can significantly contribute to the decarbonization of the global energy system through their increased power output. Two main sustainability considerations for any renewable technology that dictate whether it can fulfil its promises are efficiency and lifetime.

Perovskite-silicon tandem solar cells have made unprecedented strides in the field of photovoltaics (PV) regarding efficiency. At Oxford PV, we have demonstrated world-record efficiencies at both small-scale and full wafer scale. Last year, we revealed a 26.9% 60-cell module, which remains a record for a residential-size photovoltaic module. Nevertheless, long-term stability remains a major concern across the research community. Established PV technologies such as silicon (c-Si) and cadmium telluride (CdTe) have set the long-term stability benchmark at a 0.25-0.5% relative loss per year, with an expected lifetime of up to 25-30 years.

We are confident that perovskite PV can maintain high performance over multiple decades. In this talk, we will discuss the major R&D approaches we are following to achieve this goal. Unlike incumbent PV technologies, where outdoor performance data and knowledge of real-world degradation modes and their characteristics are available, it is imperative to deploy perovskite PV in the field before having performed outdoor testing for decades to demonstrate the reliability of the solar panels. Accelerated stress testing is designed to expose PV cells and modules to a variety of stressors that can mimic expected real-world conditions – the combined light and heat exposure test is a common route to evaluate the cumulative affect of these stressors in the field, and typically elevated temperatures are chosen to compress ‘years of operation’ into week-to-month long experiments. In this way, relevant degradation modes can be triggered and rapid iteration of technology can be made, However, it is crucial to both: a) choose the relevant parameter ranges that activate the degradation processes prominent under field-deployment conditions whilst avoiding the triggering of degradation artifacts unique to the stress conditions; and b) have consideration as to the means in which cell parameters are determined, either during, or following, stress tests.

By selecting the right stressing conditions and employing suitable models, we can calculate an acceleration factor and estimate real-world operation lifetime, which can be validated by comparing with corresponding outdoor performance data, providing reliable lifetime predictions. We will present activity at Oxford PV for each of these stages. The range of degradation modes in perovskites are well known, and have been reviewed extensively in the literature. A key consideration for enhancing cell performance longevity however, is to  identify the critical degradation modes, those that dominate the measured power output. dAt Oxford PV, we focus on identifying the link between material properties and changes with device losses for the critical degradation modes, aim to introduce mitigating routes, and move to the next critical mode. Representative examples of optimized device performance and stability will be discussed, Lastly, looking towards scalability, being able to repeatedly obtain high-efficiency and stable devices is of paramount importance. By continuously tracking our device stability, we gain more insights into the correlation of process capability and reproducibility. This allows us to identify process windows and parameters affecting performance and stability, informing the design of scalable processes that can be transferred from R&D to high-throughput manufacturing.