TECHNOLOGY EXPLAINER
Lead and Iodine
— 0.53 g of lead and 0.98 g of iodine per square metre: how to read such small numbers
In a standard perovskite absorber, about a third of the weight is lead and about 60% is iodine. Japan's Ministry of Economy, Trade and Industry (METI) calculates 0.53 g of lead and 0.98 g of iodine per m² of absorber, and notes that Japan is the world's second-largest iodine producer. This article sets out lead toxicity, containment and recovery, EU and Japanese regulation, and iodine supply, using figures from official statistics and primary documents.
- The lead and iodine question, in three points
- How much is in 1 m²
- Our calculation: how much for 1 GW, and for 20 GW?
- Lead toxicity: what public bodies say
- A materials engineer's view (1): small in quantity, but present in a form that moves when it meets water
- Containment and recovery: three directions shown in the literature
- Regulation: the EU's RoHS and WEEE, and Japan's new recycling law
- A materials engineer's view (2): “0.035% of the product” versus “33% of the homogeneous material”
- Iodine: Japan is a producer, and holds the largest reserves
- Strengths, weaknesses and open issues
- Glossary / References / Claim-to-source audit
Sourced = stated in published material or a peer-reviewed paper (link given)
Our calculation = a value this article derived from assumptions it states
Not yet confirmed = a plan or target with no confirmed track record
Structural readings and materials-design interpretations are marked separately as Commentary. How the law applies is decided product by product and case by case; nothing in this article is a legal opinion.
1. The lead and iodine question, in three points
- Lead: METI states that for perovskite solar cells “the lead contained, at around 0.5 g/m², must be properly treated and recovered”Sourced. WHO states that “there is no level of exposure to lead that is known to be without harmful effects”Sourced
- Iodine: METI notes that “for iodine, Japan is the world's second-largest producer (a share of about 30%)”, and presents this as supporting a resilient supply chain that includes raw materialsSourced
- The legal framework: in June 2026 Japan promulgated the Act on Promoting the Recycling of Solar Cell Waste (Act No. 33 of 2026)Sourced. It takes effect on a date to be set by cabinet order within one year and six months of promulgationNot yet confirmed
Judged by quantity alone, both lead and iodine look like small problems. The lead in 20 GW of absorber is about 53 t, about 0.001% of world lead mine productionOur calculation. But the lead is present as an ionic crystal that reacts readily with water, spread thinly near the surface of the product. The problem is not the total amount but the form, the location and the way regulations count it (our commentary).
2. How much is in 1 m²
METI's strategy document calculates the materials needed for 1 m² of perovskite solar cell from the thickness and density of each componentSourced.
| Absorber composition | Element | Content (by weight) | Per m² |
|---|---|---|---|
| CH3NH3PbI3 | Iodine | 61.4% | 0.98 g |
| CH3NH3PbI3 | Lead | 33.4% | 0.53 g |
| CH3NH3SnI3 | Iodine | 71.6% | 1.1 g |
| CH3NH3SnI3 | Tin | 22.3% | 0.34 g |
All Sourced (METI, Next-Generation Solar Cell Strategy, page 53 [Ref. 1]). The same document gives the absorber thickness as 300 to 500 nm (400 nm used in the calculation) and the density as 3.5 to 4.2 g/cm³ (3.9 g/cm³ used).
- Content: the formula weight of CH3NH3PbI3 is 12.011 + 6×1.008 + 14.007 + 207.2 + 3×126.904 = 620.0 g/mol. Lead: 207.2 ÷ 620.0 = 33.4%; iodine: 380.7 ÷ 620.0 = 61.4%Our calculation. These match METI's figures
- Density from another primary source: taking the cubic lattice constant of MAPbI3 reported by Weber (1978), 6.27 Å, with one formula unit per unit cell, the density is 620.0 ÷ (6.022×10²³ × (6.27×10⁻⁸ cm)³) = about 4.18 g/cm³Our calculation
- With this density and a 400 nm film, 1 m² holds 1.67 g of MAPbI3: 0.56 g of lead and 1.03 g of iodineOur calculation. This agrees with METI's values (0.53 g of lead at 3.9 g/cm³) to within about 5%
Assumptions and limits: real high-efficiency cells mostly use mixed compositions containing FA, Cs and Br, and thickness varies from product to product. The amount per m² is a guide set by composition and thickness.
3. Our calculation: how much for 1 GW, and for 20 GW?
- Assumption: module efficiency of 20% (200 W per m² under standard conditions). 1 GW = 10⁹ W ÷ 200 W/m² = 5 million m²
- Assumption: 0.53 g of lead and 0.98 g of iodine per m² (METI's values). Manufacturing losses (such as ink utilisation in coating) are not included
- Per GW: lead 0.53 × 5×10⁶ = about 2.7 t; iodine 0.98 × 5×10⁶ = about 4.9 t
- 20 GW (METI's 2040 deployment target): lead about 53 t; iodine about 98 t
Compared with official statistics:
- 98 t of iodine is about 1.1% of Japan's estimated 2025 iodine production of 9,000 t given by USGS
- 53 t of lead is about 0.001% of estimated 2025 world lead mine production of 4.5 million t given by USGS
All of these are Our calculation. About 20 GW by 2040 is a policy targetNot yet confirmed. Assumptions and limits: this assumes the 20 GW is manufactured once, with no replacements or repowering. Higher efficiency would reduce the area needed, and a different thickness or composition would change the content.
4. Lead toxicity: what public bodies say
The WHO fact sheet describes lead as followsSourced.
- Lead exposure affects multiple body systems and is particularly harmful to young children and women of reproductive age
- Lead is distributed to the brain, liver, kidneys and bones, and accumulates in the teeth and bones
- There is no level of exposure to lead that is known to be without harmful effects
- More than 3.5 million deaths in 2023 were attributed to lead exposure (mainly through cardiovascular effects; IHME estimate)
- Most of the world's lead consumption goes into making lead-acid batteries for motor vehicles
USGS likewise states that about 67% of apparent US lead consumption (2025 estimate) goes into lead-acid batteriesSourced. In other words, the lead used in perovskites is a tiny fraction of society's overall lead flows. It still matters because of the form it takes and where it sits, discussed in the next section (our commentary).
5. A materials engineer's view (1): small in quantity, but present in a form that moves when it meets water
The lead in a perovskite is not locked into a metal or a glass; it is an ionic crystal (a lead halide) spread as a sheet a few hundred nanometres thick (our commentary). As discussed in our explainer on ion migration and degradation, Leguy and colleagues reported that exposure to liquid water decomposes MAPbI3 irreversibly into PbI2Sourced.
Lead leakage is therefore a problem that arises when two conditions coincide: the product breaks, and it meets water. Jiang and colleagues (Okinawa Institute of Science and Technology, OIST) measured exactly this: lead leakage from modules damaged by mechanical impactSourced. Li and colleagues (Nature) also evaluated severely damaged devices immersed in waterSourced.
From this the design variables for countermeasures become clear (our commentary).
- Hold together when broken: the mechanical strength of the encapsulant, and its ability to close cracks by itself
- Capture whatever gets out: build functional groups that bind lead strongly (phosphonic acids, chelating agents) into the encapsulation
- Recover at the end: dissolve the perovskite after use and get the lead and iodine back
This is an area where makers of encapsulants, adhesives and coatings can contribute directly.
6. Containment and recovery: three directions shown in the literature
(1) Hold together when broken: self-healing epoxy encapsulation (Jiang et al., 2019)
Jiang and colleagues damaged modules with different encapsulation methods by mechanical impact based on a modified FM 44787 standard and measured the rate of lead leakage. They report that epoxy resin encapsulation reduced the lead leakage rate by a factor of 375 compared with glass-cover encapsulation sealed at the module edges with UV-cured resinSourced. They attribute this to the self-healing behaviour and higher mechanical strength of the epoxy resinSourced.
(2) Capture whatever gets out: on-device lead sequestration (Li et al., 2020)
Li and colleagues demonstrated a chemical approach that sequesters more than 96% of the lead leakage caused by severe damage on the device itselfSourced. On the front, a transparent molecular film bearing phosphonic acid groups that bind lead strongly is applied to the glass side of the transparent-electrode glass; on the back, a polymer film mixed with a lead-chelating agent is placed between the metal electrode and a standard solar encapsulation filmSourced. When immersed in water, these films swell rather than dissolve, absorbing lead while keeping their shape, which also makes it easy to recover lead after damageSourced.
(3) Recover at the end: water-based recycling (Xiao et al., 2025)
Xiao and colleagues reported a method that recovers all valuable components from perovskite solar cell waste using low-cost, water-based solventsSourced. Degraded perovskite can be regenerated, recovery extends to the charge-transport layers, substrates, cover glass and metal electrodes, and even after repeated degradation and regeneration, the refurbished devices matched fresh ones in efficiency and stabilitySourced. Compared with landfill, they estimate reductions of 96.6% in resource depletion and 68.8% in human toxicity (cancer effects)Sourced.
METI's strategy document, on the other hand, says of recycling technology for perovskite solar cells that it is “currently at the development stage; implementation needs to be considered with economics taken into account”Sourced. No primary source showing a working collection and recycling system for mass-produced products could be found within the scope of this articleNot yet confirmed.
7. Regulation: the EU's RoHS and WEEE, and Japan's new recycling law
| Instrument | What the text or published material says | Source |
|---|---|---|
| EU RoHS Directive (2011/65/EU) | Annex II sets the maximum concentration of lead in homogeneous materials at 0.1% by weight. Article 2(4)(i) excludes from scope “photovoltaic panels intended to be used in a system that is designed, assembled and installed by professionals for permanent use at a defined location to produce energy from solar light for public, commercial, industrial and residential applications” | EUR-Lex |
| EU WEEE Directive (2012/19/EU) | The electrical and electronic equipment covered includes photovoltaic panels (Annex I category 4, “Consumer equipment and photovoltaic panels”, among others). Annex IV lists “small equipment with integral photovoltaic panels” among examples of small equipment. Member States are asked to give priority to separate collection of photovoltaic panels, among other items | EUR-Lex |
| Japan: Act on Promoting the Recycling of Solar Cell Waste (Act No. 33 of 2026) | Enacted on 29 May 2026 and promulgated on 5 June. It obliges those intending to dispose of large quantities of commercial solar cells (solar power operators and others) to recycle in line with criteria set by the government, and requires manufacturers and importers to take measures such as environmentally conscious design and providing information on the substances their products contain. It takes effect on a date to be set by cabinet order within one year and six months of promulgation | Ministry of the Environment |
| Japan: FIT/FIP schemes | Mandatory registration of the content of four hazardous substances (lead, arsenic, cadmium and selenium) | METI |
All Sourced (EU RoHS Directive [Ref. 5], EU WEEE Directive [Ref. 6], Ministry of the Environment [Ref. 7], METI [Ref. 1]). FIT and FIP are Japan's feed-in tariff and feed-in premium schemes for renewable electricity. The Ministry of the Environment's summary of the law cites as background the expectation that discarded solar panels will reach up to about 500,000 t a year from the late 2030s onwards. The summary material this article checked contained no provisions specific to perovskite solar cells.
8. A materials engineer's view (2): “0.035% of the product” versus “33% of the homogeneous material”
The RoHS Directive sets the 0.1% lead limit per “homogeneous material”. The Directive defines a homogeneous material as “one material of uniform composition throughout or a material, consisting of a combination of materials, that cannot be disjointed or separated into different materials by mechanical actions such as unscrewing, cutting, crushing, grinding and abrasive processes”Sourced.
Here are two divisionsOur calculation.
- Divided by the whole product: 0.53 g of lead ÷ 1.5 kg/m² for a film-type module (the premise of METI's estimate) = about 0.035%, below 0.1%
- Divided by the absorber alone: lead makes up 33.4% of MAPbI3, about 330 times the 0.1% limit
Depending on how you count, the same product looks like a third of the limit or 330 times the limit. On the RoHS approach, it is the latter that counts (our commentary).
RoHS does, however, exclude photovoltaic panels installed by professionals for permanent use at a defined locationSourced. Lightweight, flexible applications — often cited as a strength of perovskites, such as integration into electronic or IoT devices — do not necessarily fall within the wording of that exclusion. That the WEEE Directive separately lists “small equipment with integral photovoltaic panels” also draws attention to this distinctionSourced. The regulatory treatment can change with the application, and this needs to be kept in mind from the stage of selecting materials and components (our commentary; how the law applies to any particular product is determined by the relevant legislation and the interpretation of the competent authorities).
9. Iodine: Japan is a producer, and holds the largest reserves
According to the USGS Mineral Commodity Summaries 2026, world iodine production is as followsSourced.
| Country | Production 2024 (t) | Production 2025, estimated (t) | Reserves (t) |
|---|---|---|---|
| Chile | 22,000 | 23,000 | 750,000 |
| Japan | 9,300 | 9,000 | 4,900,000 |
| United States | Withheld | Withheld | 250,000 |
| Turkmenistan | 800 | 800 | 70,000 |
| Iran | 700 | 700 | 40,000 |
| Azerbaijan | 210 | 210 | 170,000 |
| World total (excluding the US, rounded) | 33,000 | 34,000 | Over 6.3 million |
All Sourced (USGS, Mineral Commodity Summaries 2026: Iodine [Ref. 3]). Small production in Indonesia and Russia is omitted. China and Uzbekistan also produce iodine, but no official figures exist and USGS says their output cannot be estimated.
- Uses: USGS lists the main uses of iodine and its compounds worldwide, in descending order of consumption, as X-ray contrast media, liquid crystal displays, pharmaceuticals, iodophors (disinfectants), animal feed and fluorochemicalsSourced
- Sources: USGS says most of the world's supply comes from three areas: the nitrate (caliche) mines of Chile, the gas and oil fields of Japan, and brine wells in north-western Oklahoma in the United StatesSourced
- Domestic sources: a document from the Keiyo Natural Gas Council (Japan Natural Gas Association), dated January 2019, states that iodine produced in Chiba Prefecture accounts for about 80% of Japan's output, that brine beneath Chiba contains about 2,000 times the iodine of ordinary seawater, and that Chiba's recoverable reserves are estimated at about 4 million t (about 500 years at current production)Sourced
- Price: USGS gives the average unit value of US iodine imports (cost, insurance and freight) as US$68 per kg in 2025 (estimated)Sourced
- Production share: 9,000 ÷ 34,000 = about 26% (USGS 2025 estimate; world total excludes the US). METI puts it at “about 30%”Sourced. The difference may come from whether undisclosed US production is included in the world total, or from different reference years (our commentary)
- Reserves share: 4.9 million ÷ 6.3 million = about 78% (world reserves are “over 6.3 million t”, so the true share is lower than this)
- Iodine raw-material cost per m²: 0.98 g × US$68/kg = about US$0.07 (import unit value used as a proxy; refining and compounding costs not included)
All of these are Our calculation.
The calculation in Section 3 put the iodine for 20 GW at about 1.1% of Japan's annual outputOur calculation. In terms of quantity, there is little reason to fear that solar cells will squeeze Japan's iodine supply (our commentary).
Japanese iodine, however, is a by-product recovered from brine pumped up together with natural gasSourced (USGS, Keiyo Natural Gas Council). Chiba University's Chiba Iodine Resource Innovation Center (CIRIC) states that the current process extracts about 90% of the iodine from the brine, warns that pumping more brine to meet rising demand could also add to the environmental burden, and names better extraction efficiency as a key challengeSourced.
So the ways to increase iodine supply are not just pumping more, but also raising extraction yields and recovering iodine from end-of-life products (our commentary). The recycling by Xiao and colleagues in Section 6 could serve as a tool for circulating iodine within Japan, not only lead. When METI's strategy document talks of “building a resilient supply chain that includes raw materials”, the substance of that may lie less in mining volumes than in recovery and recycling technology (our commentary).
10. Strengths, weaknesses and open issues
| Aspect | Confirmed in primary sources | Remaining issue |
|---|---|---|
| Amount of lead | About 0.5 g per m² (METI) | Present as an ionic crystal in a thin film. Decomposes on contact with water (Leguy et al.) |
| Containment | Epoxy encapsulation cut the leakage rate by a factor of 375 (Jiang et al.). Capture layers sequester over 96% (Li et al.) | Adoption in mass-produced products and long-term performance not confirmed in this article |
| Recovery | All components recovered in a water-based process; refurbished devices match new ones (Xiao et al.) | METI describes it as “currently at the development stage” |
| Regulation | Japan has promulgated a solar cell waste recycling law (Ministry of the Environment) | Takes effect on a date set by cabinet order. RoHS treatment may vary with the application |
| Iodine | Japan is second in production and first in reserves (USGS). Chiba accounts for about 80% of domestic output (Keiyo Natural Gas Council) | Pumping more brine raises environmental concerns (CIRIC) |
Each item is Sourced (source in brackets). The sorting is this article's own framing.
(1) No comparison with lead-leakage “safety standards”
How much lead released on damage translates into what level of health or environmental risk depends heavily on conditions such as the installation site, rainfall and soil. This article does not assess leakage amounts against any particular safety standard.
(2) How Japan's new law will operate
The criteria under the new law, and the details of how new types of solar cell, including perovskites, will be treated, had not been published as far as this article could confirm at the time of researchNot yet confirmed.
- 0.53 g of lead and 0.98 g of iodine per m² of absorberSourced. A check from the formula weight agreesOur calculation
- Even 20 GW contains only about 53 t of lead and about 98 t of iodine, about 1.1% of Japan's iodine outputOur calculation
- WHO says no level of lead exposure is known to be without harmful effectsSourced
- Hold together when broken, capture whatever gets out, recover at the end — encapsulants and chemistry offer real optionsSourced
- RoHS counts per homogeneous material. About 0.035% of the product is 33.4% of the absorberOur calculation
- Japan is second in iodine production and first in reserves. The key to more supply is extraction yield and recovery rather than pumping (our commentary)
11. Glossary
- Homogeneous material
- A RoHS term: a material of uniform composition throughout, or a combination of materials that cannot be separated by mechanical actions.
- RoHS Directive
- The EU restriction on certain hazardous substances in electrical and electronic equipment. Lead is limited to 0.1% in homogeneous materials.
- WEEE Directive
- The EU framework for collecting and recycling waste electrical and electronic equipment. Photovoltaic panels are covered.
- Chelating agent
- A molecule that grips a metal ion strongly through several bonds.
- Phosphonic acid group
- An acidic, phosphorus-containing functional group that binds strongly to metal ions such as lead.
- Self-healing
- The ability of a material to close scratches or cracks through its own properties.
- Brine
- Salty water found underground. In Japan it is pumped up with natural gas and iodine is recovered from it.
- Reserves
- The quantity of a resource expected to be economically recoverable with current technology and economic conditions.
- X-ray contrast medium
- A drug that makes organs and blood vessels easier to see on X-ray images. The largest use of iodine.
- Four hazardous substances
- Lead, arsenic, cadmium and selenium, whose content must be registered under Japan's FIT/FIP schemes.
- USGS
- The US Geological Survey, which publishes the annual mineral statistics Mineral Commodity Summaries.
- Film-type
- A lightweight, flexible perovskite solar cell built on a plastic film substrate.
12. References (primary sources)
- Ministry of Economy, Trade and Industry (METI) “Next-Generation Solar Cell Strategy”, November 2024 (PDF, in Japanese) https://www.meti.go.jp/shingikai/energy_environment/perovskite_solar_cell/pdf/20241128_1.pdf
- WHO “Lead poisoning” fact sheet https://www.who.int/news-room/fact-sheets/detail/lead-poisoning-and-health
- U.S. Geological Survey “Mineral Commodity Summaries 2026: Iodine” (PDF) https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iodine.pdf
- U.S. Geological Survey “Mineral Commodity Summaries 2026: Lead” (PDF) https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lead.pdf
- EU (EUR-Lex) “Directive 2011/65/EU on the restriction of the use of certain hazardous substances in electrical and electronic equipment” (RoHS Directive) https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32011L0065
- EU (EUR-Lex) “Directive 2012/19/EU on waste electrical and electronic equipment (WEEE)” https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32012L0019
- Ministry of the Environment, Japan “Solar panel recycling” (the Act on Promoting the Recycling of Solar Cell Waste and summary material; in Japanese) https://www.env.go.jp/recycle/recycling/renewable/page_00345.html
- Li et al. “On-device lead sequestration for perovskite solar cells”, Nature 578, 555 (2020) https://doi.org/10.1038/s41586-020-2001-x
- Jiang et al. (Okinawa Institute of Science and Technology) “Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation”, Nat. Energy 4, 585 (2019) https://doi.org/10.1038/s41560-019-0406-2
- Xiao et al. “Aqueous-based recycling of perovskite photovoltaics”, Nature 638, 670 (2025) https://doi.org/10.1038/s41586-024-08408-7
- Weber “CH3NH3PbX3, ein Pb(II)-System mit kubischer Perowskitstruktur”, Z. Naturforsch. B 33, 1443 (1978) https://doi.org/10.1515/znb-1978-1214
- Leguy et al. “Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells”, Chem. Mater. 27, 3397 (2015) https://doi.org/10.1021/acs.chemmater.5b00660
- Keiyo Natural Gas Council (Japan Natural Gas Association) “Natural Gas and Iodine in Chiba Prefecture”, January 2019 (PDF, in Japanese) https://www.tengas.gr.jp/files/user/keiyokyo/Natural%20gas%20&%20Iodine_Chiba%20Pref.pdf
- Chiba Iodine Resource Innovation Center (CIRIC), Chiba University “What is iodine?” (in Japanese) https://ciric.chiba-u.jp/iodine.html
13. Claim-to-source audit
| Claim in the text | Basis | Label |
|---|---|---|
| Per m² of absorber: for MAPbI3, 0.98 g of iodine (61.4%) and 0.53 g of lead (33.4%); for MASnI3, 1.1 g of iodine (71.6%) and 0.34 g of tin (22.3%). Absorber thickness 300 to 500 nm (400 nm used) and density 3.5 to 4.2 g/cm³ (3.9 g/cm³ used). A film-type module taken as 1.5 kg/m² in the estimate. “The lead contained, at around 0.5 g/m², must be properly treated and recovered.” “Recycling technology is currently at the development stage; implementation needs to be considered with economics taken into account.” Mandatory registration under FIT/FIP of the content of four hazardous substances (lead, arsenic, cadmium, selenium). “For iodine, Japan is the world's second-largest producer (a share of about 30%).” Building a resilient supply chain including raw materials | METI, Next-Generation Solar Cell Strategy, pages 16 and 52 to 54. Reference 1 https://www.meti.go.jp/shingikai/energy_environment/perovskite_solar_cell/pdf/20241128_1.pdf | Sourced |
| The aim of deploying about 20 GW by 2040 | METI, Next-Generation Solar Cell Strategy, page 32. A policy goal, not an achievement. Reference 1 https://www.meti.go.jp/shingikai/energy_environment/perovskite_solar_cell/pdf/20241128_1.pdf | Not yet confirmed |
| That lead affects multiple body systems and is particularly harmful to young children and women of reproductive age. That it is distributed to the brain, liver, kidneys and bones and accumulates in teeth and bones. That no level of exposure is known to be without harmful effects. That more than 3.5 million deaths in 2023 were attributed to lead exposure (IHME). That most world lead consumption goes into lead-acid batteries for motor vehicles | WHO fact sheet. Reference 2 https://www.who.int/news-room/fact-sheets/detail/lead-poisoning-and-health | Sourced |
| Iodine production by country (2024 and 2025 estimate) and reserves (Chile 22,000 and 23,000 t / 750,000 t; Japan 9,300 and 9,000 t / 4.9 million t; US withheld / 250,000 t; and others), a world total excluding the US of 33,000 and 34,000 t, and world reserves of over 6.3 million t. That Chinese and Uzbek production cannot be estimated. The main uses (X-ray contrast media, liquid crystal displays, pharmaceuticals, iodophors, animal feed, fluorochemicals). The main supply regions (Chilean nitrate mines, Japanese gas and oil fields, brine wells in north-western Oklahoma). The 2025 estimated average unit value of US imports of US$68/kg | USGS, Mineral Commodity Summaries 2026: Iodine. Reference 3 https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-iodine.pdf | Sourced |
| Estimated 2025 world lead mine production of 4.5 million t. That about 67% of apparent US lead consumption goes into lead-acid batteries (2025 estimate) | USGS, Mineral Commodity Summaries 2026: Lead. Reference 4 https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-lead.pdf | Sourced |
| That Annex II sets the maximum concentration of lead in homogeneous materials at 0.1% by weight. The definition of homogeneous material. That Article 2(4)(i) excludes photovoltaic panels in systems designed, assembled and installed by professionals for permanent use at a defined location | EU RoHS Directive (2011/65/EU). Reference 5 https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32011L0065 | Sourced |
| That photovoltaic panels are within scope (Annex I category 4, “Consumer equipment and photovoltaic panels”, among others). That Annex IV lists “small equipment with integral photovoltaic panels” among examples of small equipment. Priority separate collection of photovoltaic panels, among other items | EU WEEE Directive (2012/19/EU). Reference 6 https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32012L0019 | Sourced |
| That the Act on Promoting the Recycling of Solar Cell Waste (Act No. 33 of 2026) was enacted on 29 May 2026 and promulgated on 5 June. The obligation on those intending to dispose of large quantities of commercial solar cells to recycle. Measures for manufacturers and importers, including environmentally conscious design and information on contained substances. Entry into force on a date set by cabinet order within one year and six months of promulgation. Expected discards of up to about 500,000 t a year from the late 2030s | Ministry of the Environment “Solar panel recycling” page and summary of the Act. Reference 7 https://www.env.go.jp/recycle/recycling/renewable/page_00345.html | Sourced |
| That more than 96% of lead leakage from severe damage was sequestered on the device. That a transparent molecular film with phosphonic acid groups was placed on the front glass side, and a polymer film with a lead-chelating agent between the rear metal electrode and the encapsulation film. That in water the films swell rather than dissolve, absorbing lead, and make recovery easy | Nature paper (abstract). Reference 8 https://doi.org/10.1038/s41586-020-2001-x | Sourced |
| That lead leakage rates were measured from modules damaged by mechanical impact based on a modified FM 44787 standard. That epoxy encapsulation reduced the leakage rate by a factor of 375 compared with glass-cover encapsulation sealed at the edges with UV-cured resin. That the reasons are self-healing and higher mechanical strength. That the authors are affiliated with the Okinawa Institute of Science and Technology | Nat. Energy paper (abstract of the author version). Reference 9 https://doi.org/10.1038/s41560-019-0406-2 | Sourced |
| A recycling method that recovers all components with low-cost, water-based solvents. Regeneration of degraded perovskite. Recovery of charge-transport layers, substrates, cover glass and metal electrodes. Efficiency and stability matching fresh devices after repeated degradation and regeneration. Reductions versus landfill of 96.6% in resource depletion and 68.8% in human toxicity (cancer effects) | Nature paper (abstract). Reference 10 https://doi.org/10.1038/s41586-024-08408-7 | Sourced |
| The cubic lattice constant of MAPbI3, 6.27 Å | Z. Naturforsch. B paper (abstract). Reference 11 https://doi.org/10.1515/znb-1978-1214 | Sourced |
| That liquid water decomposes MAPbI3 irreversibly into PbI2 | Chem. Mater. paper (abstract). Reference 12 https://doi.org/10.1021/acs.chemmater.5b00660 | Sourced |
| That iodine produced in Chiba Prefecture accounts for about 80% of Japan's output. That brine in Chiba contains about 2,000 times the iodine of ordinary seawater. That Chiba's recoverable reserves are estimated at about 4 million t (about 500 years at current production) | Keiyo Natural Gas Council (Japan Natural Gas Association) document (January 2019). Reference 13 https://www.tengas.gr.jp/files/user/keiyokyo/Natural%20gas%20&%20Iodine_Chiba%20Pref.pdf | Sourced |
| That iodine extraction from brine is about 90%. That pumping more brine to meet demand could add to the environmental burden. That improving extraction efficiency is a key challenge | Chiba University CIRIC, “What is iodine?”. Reference 14 https://ciric.chiba-u.jp/iodine.html | Sourced |
| The check of the 620.0 g/mol formula weight and contents (lead 33.4%, iodine 61.4%, MA 5.2%). The density of about 4.18 g/cm³ from the lattice constant, and 0.56 g of lead and 1.03 g of iodine per m². At an assumed 20% efficiency, about 2.7 t of lead and 4.9 t of iodine per GW, and about 53 t and 98 t for 20 GW; about 1.1% of Japan's iodine output and about 0.001% of world lead mine production. Lead at about 0.035% of the whole product versus 33.4% of the homogeneous material (about 330 times 0.1%). Japan's iodine production share of about 26% and reserves share of about 78%. An iodine raw-material cost of about US$0.07 per m² | Our calculation. A module efficiency of 20%, excluding manufacturing losses, and using the import unit value as a proxy for iodine cost are assumptions set by this article. Includes the numerical parts of Figs. 1, 2 and 4 | Our calculation |
| The date of entry into force, the criteria under the new law and the details of how perovskite solar cells will be treated. A working collection and recycling system for mass-produced products | Entry into force is to be set by cabinet order, and the details could not be confirmed at the time of research (our note based on the content of Reference 7). No primary source showing working recycling of mass-produced products could be confirmed either | Not yet confirmed |
| The framing that the problem lies in form, location and counting rather than total amount. Positioning the lead as an ionic crystal present as a film. The framing “hold together when broken, capture whatever gets out, recover at the end”. The reading that the RoHS exclusion does not necessarily cover lightweight or embedded applications (not a legal opinion). The reading that the key to more iodine lies in extraction yield and recovery. Our inference as to why the USGS and METI shares differ | Our summary and commentary based on published content. Not views expressed by the institutions | Commentary |
| A comparison of lead leakage amounts with safety standards | Heavily condition-dependent; not assessed in this article (our note) | Commentary |
| That Figs. 1 to 4 are explanatory drawings, not real cross-sections or the statistical charts themselves. That the hero image and Fig. 5 are AI-generated images | Our note | Commentary |
Last updated 25 September 2026. Sources are limited to primary material (a government strategy document and legislation pages, USGS official statistics, WHO, the Official Journal of the EU, peer-reviewed papers, and material published by an industry body and a university). No market-size or price-outlook estimates from research firms are used. A safety assessment of lead leakage amounts, the detailed operation of Japan's new law and the operating status of recycling for mass-produced products are not stated, because no primary source could be confirmed. Statements about regulation describe the content of legal texts and published material and are not legal opinions on how they apply to any particular product. All figures are explanatory concept graphics. Figs. 1 to 4 are vector drawings; the hero image and Fig. 5 are AI-generated images, and none of them shows a real cross-section photograph, raw material or recycling facility.