In recent years, remarkable progress has been made in the field of perovskite solar cells, resulting in power conversion efficiencies (PCE) surpassing 26%. The vast majority of research efforts are dedicated to the processing of perovskites from solution, often from highly toxic solvents.[1] While this is manageable for lab-scale fabrication, the use of such solvents raises considerable concerns regarding the possibility to fabricate perovskite devices on the mass scale. In this talk, I will present a strategy towards the selection of more sustainable solvent alternatives for the deposition of perovskite layers. The strategy is based on the utilization of Hansen solubility parameter space for the prediction of suitable solvents and solvent-antisolvent systems.[2] I will also present alternative deposition methods which are solvent free, and can be more easily scaled up in a sustainable manner.[3]

[1] “Sustainability in Perovskite Solar Cells”, K. P. Goetz, A. D. Taylor, Y. J. Hofstetter and Y. Vaynzof,

ACS Appl. Mater. Interfaces 13, 1, 1 (2021).

[2] “Solvent–antisolvent interactions in metal halide perovskites”, J. R. Bautista-Quijano, O. Telschow, F. Paulus, Y. Vaynzof, Chem. Comm. 59 (71), 10588-10603 (2023).

[3] “The Future of Perovskite Photovoltaics – Thermal Evaporation or Solution Processing?”, Y. Vaynzof,

Adv. Energy Mater. 10, 48, 2003073 (2020).

Recently, flexible Perovskite Solar Cells (f-PSC) have been a growing niche within the research on PSC with the aim of broadening its range of applications toward light-weight Building Integrated Photovoltaics (BIPV), Internet of Things (IoT), portable electronics and even space applications. [1] This is mainly related to the higher power-to-weight (PWR) ratio of flexible devices compared to glass-based counterparts. [2] However, to unlock f-PSC full potential, research must focus on boosting the sustainability of the cell, besides its performance and stability. Sustainability concerns mainly deal with the use of organic Hole Transport Materials, whose synthesis has a huge impact on the overall score of the final device, especially when polymeric HTMs are considered.

Indeed, state of the art polymeric HTMs, such as poly(triarylamine) (PTAA), are still processed with toxic solvents such as chlorobenzene (CB), dichlorobenzene (DCB) or toluene, [3] which pose an obvious barrier to the upscaling of this technology. As the literature in green-solvent-deposition charge transport layers is still scarce, we present a new set of HTMs processed using Tetrahydrofuran (THF) that is a non-aromatic, non-halogenated, cheap low environmental risk solvent and has low human health toxicity. [4] We find that the choice of green solvent processable HTM’s is a defining parameter for polymers when compared to small molecules, due to their limited solubility resulting from prioritising extended 𝜋-𝜋 conjugation frameworks, [5] yielding this study even more promising to the sustainable upscaling of f-PSCs.

Throughout this work, the four newly synthetized HTMs incorporate additional scaffolds to modify the conventional triphenylamine moiety characterizing the PTAA, with the scope of improving their solubility in THF. Aiming at this, the phenothiazine moiety was opted due to its good solubility in common organic solvents, high chemical stability, high tunability, high hole mobilities and extremely low cost. [6] The methyl substitution of the TPA phenyl unit was also altered to evaluate the trade-off effect on solubility and polymeric chain packing. As an alternative to PTZ-PTAA polymers, we also considered the benzothiadiazole unit due to its electron deficient system, [7] giving rise to the ability to tune the electronic properties of the final HTM. To the best of our knowledge, the coupling of these three scaffolds in a polymeric system has never been reported.

The novel polymers P1-4 were successfully synthesized using specially optimized protocols, adhering to Green Chemistry Principles, [8] and thoroughly characterized in terms of structural, optoelectronic, and thermal properties. All the polymers have appropriate band gaps and a HOMO energy levels aligned with the valence band of the active layer, assuring fast and efficient charge extraction. Additionally, they are thermally stable well above operating standard temperatures and could withstand high annealing temperatures.

After their characterization, P1-4 were implemented as HTMs on flexible n-i-p devices using PTAA as the reference. Results reveal that P1-4 can achieve competitive efficiencies compared to PTAA when the latter is processed with toluene, and even outperform the reference processed with THF.

This work will serve as a baseline for the pursuit of increasing environmentally friendly, solution processable materials (e.g BioRenewable sources, 2-MeTHF), paving the way toward highly efficient, stable, and sustainable f-PSCs to enter the market.            

Perovskite solar cells (PSC) have experienced a dramatic improvement of power conversion efficiency (PCE) in just one decade, from ~10% to the current 26.1% [1]. The high efficiency and the device manufacturing based on low-cost solution processing, which spares high temperature and vacuum, have attracted the interest of academia and industry and substantial funding from governments and supranational institutions.Generally fabricated on rigid glass, PSC can be also made on flexible foils, achieving record PCE of 24.6%  on small area and opening up to a wide range of applications, where heavy and fragile rigid glass would be less suitable: IoT sensors, retrofitting of existing buildings, i.e. building-applied PV, space. Flexible perovskite solar cells (f-PSCs) have been demonstrated on large area substrates, reaching up to 15.5% PCE on 100 cm² modules [3], with the perovskite layer only deposited via blade coating and the remaining layers by spin coating.</p> <p>To demonstrate f-PSC on large scale and make the technology appealing to industry, reliable and sustainable fabrication routes, compatible with high throughput roll-to-roll manufacture, must be developed. Thus far, most studies of f-PSCs are focusing on small-scale methods and hazardous solvents such as DMF, NMP, and 2-ME. Here, we present f-PSC with device architecture of PET/ITO/SnO 0.1 FA 0.9Pb(I 0.94 Br 0.06 ) 3 / PTAA/Au, in which both the electron transport layer and the absorber are deposited by air-flow assisted blade coating method on 5&times;7 cm2  flexible substrates. Notably, the perovskite layer is deposited in ambient air via a double-step method, starting from our previous work[4] and changing solvent system, using a DMF-free solvent system, i.e. DMSO only. By fine-tuning the coating parameters, we obtained promising results in terms of PCE reaching 12.7% for 2.5&times;2.5 cm 2 cells obtained from cutting large-area substrates. In addition, to demonstrate the scalability of this double-step perovskite deposition method, we successfully deposited films on flexible substrates up to 10&times;10 cm

Perovskite solar technology has rapidly demonstrated its commercial potential within just over ten years of intense research efforts worldwide. Its remarkable attributes, including high specific power, cost-effective production, and superior performance in low-light conditions, have significantly enhanced its value across various applications, distinguishing it from other photovoltaic technologies. Hybrid organic-inorganic perovskites merge the benefits from both realms: the ease of solution processing inherent in organic small molecules or polymeric semiconductors, as seen in organic polymer solar cells, and the exceptional physical characteristics of high-performance (poly or single)-crystalline inorganic semiconductors. This fusion creates a single material class that encompasses the advantages of both.

Sustainable, safe and industry compatible processing routes are paramount to enable large scale production of perovskite photovoltaics. Green and sustainable perovskite photovoltaics are not only enabled by the choice of processing, but sustainability starts already at the material level!

Sustainable perovskite precursor synthesis is enabled by novel and innovative green halide chemistry developed by Solaveni in Germany.[1] In this talk, the advantages of the novel synthesis routes for organic alkylammonium halides as well as metal halides (PbX₂, SnX₂; X= halide) are highlighted and benchmarked from an LCA perspective against the conventional production routes. The LCA analysis delves into the specific environmental impacts of these precursor materials, assessing factors such as resource consumption, energy use, and emissions, offering critical insights into their sustainability profiles and contributing to the overall understanding of the ecological footprint associated with such materials.

Furthermore, we present the latest developments in lead-free tin halide perovskite solar modules obtained via industry compatible coating techniques using Solaveni’s custom made SnI₂ inks.[2]

Organic-inorganic Pb halide perovskite (HaP)-based solar cells have shown great promise as a sustainable and economic way of electricity generation as its power conversion efficiencies skyrocketed to over 25% [1] within a decade of its introduction. To date, all the best-performing HaPs contain Pb and are fairly soluble in water.  Pb is considered a hazardous heavy metal with major health concerns affirmed by various international organizations with recommended restricted levels of Pb in potable water (10-15 µg/L) [2]. One of the challenges of this technology is its potential environmental hazard of accidental Pb leached from broken cells/modules due to failure of encapsulation/packaging, vandalism, hail, storm, and subsequent rain. Quantifying the environmental hazard of accidental Pb²⁺ leaching, i.e., the reactivity and mobility of Pb²⁺ leached from HaP-based solar cells into the soil and from there to groundwater, was the goal of this research. Pb²⁺ originated 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. We measured, analyzed and simulated the penetration depth profile of Pb²⁺ from HaPs and non-HaP sources into 3 types of agricultural soil under typical rain conditions, and its adsorption mechanism to the soil was described [2]. Most of the leached Pb²⁺ was 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 irrespective of its sources and types of soil [3]. At conditions relevant to outdoor damage to HaP-based solar cells, it was found that the Pb²⁺ content retained by the topsoil is at least 100 times smaller than that of their maximum adsorption capacity. Surprisingly, organic co-cations from the dissolved HaP are found to enhance the Pb²⁺ adsorption capacity, compared to non-HaP-based Pb²⁺ sources. Our findings suggest that Pb²⁺ from damaged HaP-based solar cells is unlikely to contaminate groundwater, hence mass-scale utilization does not imply an environmental hazard. Panel installation over soil types with improved Pb²⁺ adsorption, regular inspection and removal of only the contaminated topsoil, are sufficient means to make the technology innocuous.

Although tin-based perovskite solar cells (PSCs) are regarded as a good replacement for lead-based PSCs due to their environmental friendliness and a suitable band gap, tin-based PSCs still have stability and efficiency issues to overcome related to their fabrication process. Specifically, it is well known that DMSO, the most popular solvent used in the fabrication of hybrid perovskites, triggers the oxidation of Sn²⁺ to Sn⁴⁺. Additionally, tin-based perovskite materials suffer from uncontrolled crystallization, leading to a high density of defect states and non-radiative recombination sites. Here, we explore solvent alternatives to DMSO with the aim of  preventing Sn²⁺ oxidation and reducing the density of defect states and unnecessary non-radiative recombination sites. Moreover, we test the photovoltaic performance and stability of the devices, as compared to those prepared with a DMSO-containing solvent system and correlate it to the optoelectronic and charge carrier dynamics properties of the tin-based perovskite materials.

Keywords: tin-based PSCs, solvent engineering, DMSO-free.

Tin halide perovskites are the main candidate for developing successful non-toxic alternatives to Pb-based materials, with great potential for a variety of applications. However, tin perovskites face serious challenges that originate from their intrinsic chemical characteristics. Apart from the oxidation of Sn(II) component, these materials are known to have limited processability: Their thin films are of lower quality, have a lower defect tolerance, and on top of that their fabrication conditions are strongly restricted to a few substrates and solvents. These aspects are accountable for the stagnation of the efficiency values around 15% in the particular case of tin perovskite solar cells. However, the fundamental properties determining their fast and ineffective crystallization remain essentially unexplored.

In this work, we have defined the factors influencing tin perovskite precursor solution properties the extent of their impact in crystallization. We carried out a comprehensive characterization of solutions in a wide range of solvents, concentrations and compositions, using a novel combination of solution and film characterization techniques, with particular interest on nuclear magnetic resonance and synchrotron-based small-angle X-ray scattering. This study does not only provide detailed instructions for the efficient preparation and processing of tin perovskite solutions, but also introduces critical fundamental information applicable to other metal halide perovskite materials, including other Pb-free ones.

Sn-based perovskite solar cells (Sn-based PVK-PV) are attracting attentions, because these bandgaps (1.2 -1.4 eV) are narrower than that of Pb-PVK-PV (wider than 1.55 eV). All-perovskite tandem cells are composed of the top cell having 1.6-1.8 eV band gap (Pb-PVK-PV) and the bottom cell having 1.1-1.3 eV band gap (Sn-based PVK-PV). 28.2 % has been reported as the highest efficiency of the tandem cell [1]. To improve the tandem solar cell efficiency, optimization of the Pb-PVK-PV for the top cell, the Sn-based PVK-PV for the bottom cell, and the interconnecting layer are needed. We have reported Pb-free Sn-PVK-PV with 14.6% efficiency [2,3] and SnPb-PVK-PV with 23.3% efficiency [4]. In this presentation, recent progresses of these two Sn-based PVK-PVs in our Lab and those of all-perovskite solar cells are reported. PEDOT-PSS is commonly employed as the hole transport layer (HTL) for the Sn-based PVK-PV. However, it has been reported that low stability is caused by the PEDOT-PSS. This prompted us to develop PEDPT-PSS-free Sn-based PVK-PV. Recently, we found that SnOx was effective for the HTL of the Sn-PVK-PV, even though SnO2 family is well-known as the electron transport layer. The basic structure is FTO glass/SnOx/Sn-PVK/C60/BCP/Ag. Efficiency over 14% and the carrier dynamics are reported. The direct Sn metal deposition on the perovskite to reduce Sn4+ concentration is included in the presentation[2,3]. As for SnPb-perovskite solar cells, the relationship between the high temperature stability and the cell structures are discussed. The stable SnPb-PVK-PV at 85 ℃ is reported. Finally, All-perovskite tandem solar cells (26-27 % efficiency) consisting of Pb-PVK PV (top cell) and PbSn-PVK PV (bottom cells) are reported [5].

Metal halide perovskites constitute a very attractive class of materials for optoelectronic applications, including solar cells, light-emitting diodes, lasers, and photodetectors. Most notably, solid-state photovoltaic devices have reached a power conversion efficiency (PCE) of 26% within only a decade of academic research.

In my talk I will discuss the special case of perovskite PV technology, focusing on devices made on flexible substrates, outlining industrial opportunities of this technology, with new value propositions and market versatility. One of the exceptional features of metal halide perovskites is bandgap tunability in a broad spectral range, which enables the facile fabrication of multijunction all-perovskite PV systems. I will address the topic of all-perovskite tandems, discussing the challenges of scalable production.

Moreover, I will provide insight into physical processes occurring during solar cell operation, especially at the interfaces with charge selective contacts, where most of the performance losses take place. Importantly, these non-optimal operations have a major influence on the long-term device reliability. Systematic interfacial engineering, combined with spectroscopic characterization of recombination losses, can lead to significant improvements in performance and stability. I will demonstrate flexible perovskite solar cells successfully passing IEC-based accelerated aging tests, where device engineering was complemented with robust flexible packaging.

Perovskite solar cell (PSC) technology [1] [2] is very promising for the generation of solar energy. However, the main impediment toward the large-scale commercial utilization of PSCs lies in their sensitivity to moisture, with the metal top electrode being one of the primary sources of degradation [3]. As a result, the development of effective solutions to prevent metal-electrode-induced degradation is critical to enable the full potential of PSCs. To prevent device degradation, several methods are being used, including optimizing the hole transporting layer (HTL), which is crucial in device operation since it acts as a protective layer for the perovskite absorber layer against environmental influences such as humidity [4].[MB1] To address the problem, this work explores a low-temperature n-i-p device architecture on flexible substrate in which a hydrophobic carbon-based electrode deposited by blade coating replaces the conventional thermally evaporated gold top electrode. Carbon electrodes are considered as a greener alternative compared to gold counterparts, due to the low-cost of the starting material that can be easily processed using simple fabrication techniques. Moreover, they could be derived from natural sources or wastes enabling a circular route [5]. Additionally, the low-temperature carbon-based PSC devices show numerous advantages, such as the ability to integrate a planar hole transport layer (HTL), a better control over perovskite crystallization, and a good compatibility with flexible substrates, roll-to-roll fabrication by using scalable deposition techniques (e.g. screen printing, inkjet printing and doctor blade coating). However, the power conversion efficiency of carbon-based PSCs still lower than that of conventional gold-based counterparts due to the inefficient charge transport and collection and poor perovskite/carbon interfacial contact.

Throughout this work, a screening of the different hole transporting materials (HTM) is carried out aiming at finding the most promising candidate to improve the performance and stability of the Carbon-based PSCs. In doing this, copper(I) thiocyanate (CuSCN), was employed as HTL since it combines intrinsic hole-transport (p-type) characteristics with wide band gaps larger than 3.5 eV [6]. At the optimized concentration, and without using any dopants, a power conversion efficiency (PCE) of 8.4% was achieved on a 1 cm² active area device. The obtained results were compared with the performance of both HTL-free devices (as internal reference) and of gold-based devices using PTAA as HTM (as state-of-art reference).

The optimization of the HTL, allowed for the demonstration of a significant improvement in the performance of the device, which could pave the way for the large-scale commercialization of PSCs with low environmental impact and promising cost-effectiveness.

Perovskite Solar cells are skyrocketing in the scientific PV scenario recently exceeding a power conversion efficiency of 26% in single junction configuration and approaching 34% in tandem configuration under standard AM1.5G illumination. Despite the high efficiencies reached to date, to close the performances gap with Silicon PV, an efficient upscaling process need to be demonstrated at industrial level, whilst long-term stability (>20 years lifetime) under outdoor conditions still needs to be proven. On the other side, Perovskite technology recently attracted attention as the most suited marketable solution for low power PV, working in diffused or low-light condition (indoor) for which the theoretical PCE limit is larger than 50%. Innovative low-power applications, such as IoT, low-power electronics, sensors, domotics and various devices working indoor, have a lifetime reduced to few years, thus representing a ready solution as launching pad of this technology. The combination of sustainable and low-cost fabrication routes for high-efficient devices to power low-energy consumption devices is a key for a first stage commercialization. Here we present possible approaches to fabricate efficient and low-cost devices avoiding the utilization of expensive benchmark materials, such as organic HTMs and metallic electrodes (i.e. Ag or Au), substituted with printed Low-Temperature carbon electrode. The combination of interface engineering and the integration of commercial low-Temperature Carbon pastes will lead to efficient HTM-free large area single cells and minimodules capable to power small electronics under indoor illumination conditions. We demonstrated to achieve efficiency above 23% and 20% respectively for low-cost single cells and minimodules. In addition, the full low-temperature processes pave the way to large scale flexible perovskite PV achieving high power-per-weight innovative application and devices.

If Earth’s economical systems continue to rely on linearity, by 2060 we will need at least two planets to meet the current materials demand. This renders the circular design of new technologies a crucial strategy to achieve sustainable production and consumption, as required by the 12^th Sustainable Development Goal of the Agenda 2030.

Within the photovoltaic field, perovskite solar cells (PSCs) have become promising alternatives to more energy-demanding, mainstream technologies, due to their low levelized cost of electricity and carbon footprint.[1,2] With the aim of approaching circularity in the emerging photovoltaic industry, it is compelling to forsee a recycling strategy for PSCs.

In this work, we perform the recycling of all critical components of n-i-p PSCs, i.e. indium tin oxide/tin oxide (ITO/SnO₂) substrate, lead iodide (PbI₂) and N²,N²,N²′,N²′,N⁷,N⁷,N⁷′,N⁷′-octakis(4-methoxyphenyl)−9,9′-spirobi[9H-fluorene]−2,2′,7,7′-tetramine (SpiroOMeTAD). Our approach involves the sequential and selective dissolution of the hole-transporting material (SpiroOMeTAD) and active material (perovskite) with green solvents, such as ethyl acetate and distilled water. Then, the collected materials are purified: SpiroOMeTAD is washed and extracted with distilled water, while PbI₂ is separated from the organic components of the perovskite and re-crystallized employing ethanol. Finally, the as-obtained SnO₂/ITO substrates are cleaned with water, acetone and isopropyl alcohol and re-used, together with refurbished PbI₂ and SpiroOMeTAD, to fabricate recycled PSCs. Since our aim is to establish a sustainable and circular method, we recover the employed solvents by distillation and we reuse them.

By analyzing the purity of recovered materials and by comparing the photovoltaic performances of PSCs fabricated with fresh and recycled materials, we demonstrate the efficacy of our recycling protocol.

Photovoltaic (PV) module production in the multi-TW scale is required for cost-efficient climate change mitigation. In the coming decades, a substantial fraction of this market may be provided by perovskite solar cells (PSC) and perovskite-based tandem concepts. Although the thin-film perovskite PV concepts require minute layer thicknesses, the huge required annual PV production rates of thousands square kilometers imply material demands in the range of kilotons. This raises the questions which materials and processes chemicals are sufficiently abundant, what is the impact of the CO2e emissions, and how the accumulating waste streams can be recycled.

First, we discuss the CO2e emissions of state-of-the art silicon as well as perovskite PV technologies. We show that, although the carbon footprint of silicon PV technologies is much lower than that of fossil fuel-based energy technologies, even with continued technological learning, the CO2e emissions of the PV industry may require 4 to 11% of the remaining carbon budget to limit global warming to 1.5°C. With perovskite PV technologies, the CO2e emissions can be further reduced to the lower boundary represented by the glass substrate.

Moreover, we present a comprehensive quantitative assessment of the material demand for multi-TW scale perovskite PV production. The supply criticality is assessed by comparing inorganic and synthetic material demands with current production rates and by estimating the scalability of material production. We find that scaling perovskite PV production is feasible from a material perspective and that the it is valid to claim that PSC are “made from abundant materials”. However, a range of materials which are commonly applied in highest-efficient PSC have been identified as critical in supply: Indium and gold used in transparent and opaque electrodes and interconnection layers must be replaced. Current cesium mining is several orders of magnitudes below the required production. This finding is especially critical for the research on stable high-bandgap inorganic perovskites. Furthermore, with the exception of PEDOT:PSS, the synthesis routes of the organic hole transport materials are currently incompatible with industrial upscaling. In contrast, the industrial production of most synthetic nanoparticulate materials has sufficient maturity. The supply of organic solvents is also not critical.

Finally, the foreseeable massive material waste streams mandate that researchers adapt a design-for-recycling thinking already in early stages of technology development. Possibilities to realize this are demonstrated by an approach to remanufacture fully encapsulated perovskite solar mini-modules.

Overall, we show that besides the improvement of efficiency and stability, the perovskite PV research community should also focus on the various aspects of long-term sustainability considerations.

In last decades halide perovskites have emerged as strong candidates for widespread applications in the field of optoelectronics and solar cells [1]. Due to the significant progresses obtained in photoconversion yield during last years [2], metal halide perovskite-based devices have enabled competitive technical performance compared with that of commercialized rivals. In the context of the technological lab and semi-industrial development of an emerging technology, such innovative materials might greatly benefit from environmental sustainability assessment in an eco-design perspective. The use of inorganic-based sensitizers, the consumption of organic solvents during the synthesis of perovskite, the use of critical raw materials and the energy and resources efficiencies of processes used during the manufacturing of cells and modules are some of the main issues that need to be considered to have an exhaustive evaluation of the environmental profile of these innovative devices [3]. Stemming from the research output on sustainability of halide perovskite solar cells [4-7], in this work we present the advantages and insightful perspectives that life cycle assessment can provide to support the eco-design of innovative devices.

Future societies must rely on clean energy sources based on sustainable technologies, and any sustainable technology must: a) generate enough power with reduced space usage (efficiency); b) be cost-effective and c) not be detrimental to the environment or society. In addition, if the goal of that technology is generating green energy to fight climate change, d) durability is to be added to these main requirements. In the global scenario of technological implementation of renewable energies, metal halide perovskites (HaP) have the potential to fulfill these criteria. However, they require a radically new approach, diverging from the roadmap followed by previous technologies. The stability of HaP devices still trails standard silicon solar cells. Long-term stability appears to be restrained by the soft nature of HaPs.

To address the present instability issues and ensure long-term effectiveness, new approaches based on remanufacturing are imperative. Remanufacturing aims to recover value from used perovskite modules by reusing glass and other components, restoring the module to a like-new condition. Additionally, recycling lead and electrodes is crucial to avoiding environmental burdens.

Remanufacturing leverages the low cost of new photovoltaic materials, their minimal environmental impacts, and the innovative design possibilities offered by new encapsulation systems. In this context, the sustainability assessment of remanufacturing is more influenced by life cycle costs than environmental impacts. Compared with a passivated emitter rear cell (PERC) module with the same photoconversion efficiency (PCE), even after 10 remanufactures, the carbon footprint and energy payback time of HaP are lower than those of PERC. However, economic studies indicate that up to three remanufactures within a 25-year lifespan, with a 5% discount rate and an average PCE of 15%, are feasible to match the same levelized cost of electricity (LCOE) as silicon crystalline modules.

The feasibility of remanufactures is influenced by various parameters, introducing uncertainty at this early technology readiness level. Some parameters are inherent to HaP, such as PCE for large areas, the cost of delamination, and the final minimum sustainable price. However, certain economic parameters, such as the economic discount rate or the price of PERC, are external to HaP.

We find ourselves at a pivotal juncture, wherein we possess the opportunity to steer the trajectory of solar energy's future toward enhanced sustainability through the strategic application of design principles aimed at facilitating recycling. This endeavor involves drawing valuable lessons from past experiences with silicon, acknowledging its challenges in the realm of recycling.