TECHNOLOGY EXPLAINER
Tin-Based Perovskites
— take out the lead, and the fight moves to oxygen
Putting tin, lead's neighbour in group 14, on the B site in place of lead is the leading route to lead-free perovskites. In theory tin gives a more favourable bandgap than lead, yet the ease with which Sn²⁺ oxidises to Sn⁴⁺ has held back both efficiency and lifetime. This article reads that chemistry through a materials lens and explains why precursor purity, additives and interfaces turn out to be decisive.
- What tin-based perovskites are, in three points
- Is tin a drop-in replacement for lead? Radius and tolerance factor
- The weak point is Sn²⁺ oxidation: what happens
- Oxidation breeds oxidation: the SnI4 and iodine cycle
- A materials engineer's view (1): identical by X-ray diffraction, yet the precursors differed
- Our calculation: how much oxygen oxidises 1% of the tin in 1 m²?
- Four layers of countermeasures: precursors, additives, crystal and interfaces
- Where efficiency stands
- A materials engineer's view (2): lead-free does not mean harmless
- 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.
1. What tin-based perovskites are, in three points
- What changes: the B site of ABX3 moves from lead (Pb²⁺) to tin (Sn²⁺). In 2014 Noel and colleagues reported the first completely lead-free CH3NH3SnI3 cells, at over 6%, obtaining an open-circuit voltage above 0.88 V from a material with a 1.23 eV bandgapSourced
- What is hard: in the same paper Noel and colleagues state that the instability of tin in its 2+ oxidation state was the biggest obstacleSourced. Stoumpos and colleagues likewise report that Sn compounds oxidise readily, becoming p-type through Sn⁴⁺ doping and showing metallic conductivitySourced
- How far it has come: a 2025 Nature paper reports 17.89% (certified 17.71%, reverse scan) for a small-area tin-based cell and 14.40% at 1 cm²Sourced (details in Section 8)
The problem with tin-based perovskites is less tin itself than tin's oxidation state. Converting even a little Sn²⁺ into Sn⁴⁺ pushes the film from semiconductor towards metal-like behaviour. So the countermeasures span the whole process: bring no Sn⁴⁺ in with the precursors, create none during film formation, and let none form in service (our commentary).
2. Is tin a drop-in replacement for lead? Radius and tolerance factor
Tin and lead both belong to group 14 and both form 2+ ions. From measured bond lengths in halides, Travis and colleagues estimated six-coordinate cation radii in iodides of 0.97 Å for Sn²⁺ and 1.03 Å for Pb²⁺Sourced. The same paper notes that Shannon's radius table does not list Sn²⁺ at all (other researchers had been using 1.15 Å)Sourced.
t = (rA + rX) ÷ [√2 × (rB + rX)], with rX (I⁻) = 2.20 Å, and rA of 2.16 Å for MA⁺ and 2.53 Å for FA⁺ (both from Travis et al.) and 1.88 Å for Cs⁺ (Bartel et al.'s value, as used in our explainer on perovskite basics)Our calculation.
- Sn (0.97 Å): MASnI3 = 0.97, FASnI3 = 1.06, CsSnI3 = 0.91
- Pb (1.03 Å): MAPbI3 = 0.95, FAPbI3 = 1.04, CsPbI3 = 0.89
How to read it: because B is smaller, t rises slightly for the same A. Geometrically, tin is an almost drop-in replacement for lead, and Stoumpos and colleagues also report that Sn–Pb solid solutions form across the whole composition rangeSourced. In other words, the problem is not shape but chemistry: the stability of the oxidation state (our commentary).
| Item | Tin-based (reported) | Lead-based (reported) | Source |
|---|---|---|---|
| Bandgap | MASnI3: 1.23 eV (Noel et al.) / 1.35 eV (Hao et al.) | MAPbI3: 1.55 eV (Hao et al.) | Noel et al. / Hao et al. |
| Long-wavelength limit of absorption | Spectral response to 950 nm in CsSnI3 (Kumar et al.) | — | Kumar et al. |
| Mobility | Estimated above 2,000 cm²/(V·s) for electrons and above 300 cm²/(V·s) for holes in MASnI3 | — | Stoumpos et al. |
| Susceptibility to oxidation | Sn⁴⁺ doping makes it p-type and metallic | — | Stoumpos et al. |
| Metal per m² | 0.34 g of tin in MASnI3 | 0.53 g of lead in MAPbI3 | METI |
All Sourced (Noel et al. [Ref. 2], Hao et al. [Ref. 10], Kumar et al. [Ref. 3], Stoumpos et al. [Ref. 1], METI [Ref. 12]). Reported bandgaps for MASnI3 vary, and Stoumpos and colleagues note that the properties depend strongly on the preparation method. “—” marks items for which this article gives no comparison value.
3. The weak point is Sn²⁺ oxidation: what happens
Lead is comfortable staying 2+ while keeping its 6s² electrons, whereas tin readily becomes 4+ (our commentary). When Sn²⁺ in a perovskite turns into Sn⁴⁺, the film becomes hole-rich p-type and starts to show metal-like conductivity (Stoumpos et al.)Sourced. Shao and colleagues identify the main reason for the low efficiency of tin-based cells as a high background carrier density caused by numerous intrinsic defects such as tin vacancies and oxidised species (Sn⁴⁺)Sourced.
Kumar and colleagues showed that adding SnF2 to CsSnI3 lowers the defect concentration and the background carrier density, giving high photocurrentsSourced. SnF2 has since become the standard additive for tin-based perovskites; Nakamura and colleagues write that they added 10 mol% SnF2, following a widely used methodSourced.
4. Oxidation breeds oxidation: the SnI4 and iodine cycle
Lanzetta and colleagues studied the degradation of (PEA)0.2(FA)0.8SnI3 2D/3D films and revealed the following cyclic degradation mechanismSourced.
- Oxygen-driven degradation produces SnI4Sourced
- SnI4 is rapidly converted into iodine (I2) by the combined action of moisture and oxygenSourced
- Iodine is a highly aggressive species that oxidises the perovskite further, producing more SnI4, and so a cyclic degradation is establishedSourced
- Film stability depended strongly on the hole-transport layer chosen as the underlying layerSourced
Once started, it accelerates itself: that is what makes it qualitatively different from degradation in lead-based perovskites (our commentary). Keeping out the first small amount of Sn⁴⁺ (or SnI4) has a large effect on lifetime later on.
5. A materials engineer's view (1): identical by X-ray diffraction, yet the precursors differed
The group of Atsushi Wakamiya at Kyoto University's Institute for Chemical Research (Nakamura et al.) obtained commercial SnI2 from three suppliers and compared it with an SnI2(dmf) complex they purified themselvesSourced. The results are highly instructive for materials peopleSourced.
- X-ray diffraction: films made from every SnI2 showed no difference in their diffraction patterns
- Optical absorption: only the film made from SnI2 containing about 10 wt% SnI4 could be told apart, by a shifted and broadened absorption edge. The other three were essentially the same
- Photoluminescence (PL): the source of the SnI2 could be clearly distinguished by PL intensity and lifetime. Films from the purified complex had the longest lifetime and highest intensity, yet even their lifetime was a short 2 to 4 ns, suggesting that some Sn(IV) still remained
What this tells us is that a precursor can pass a crystal-structure check (XRD) and still fail electronically (our commentary). Because a trace of Sn(IV) governs performance in tin-based perovskites, the yardstick for incoming inspection has to move from “is the phase right?” to “is the oxidation state pure?”.
Our calculation: if SnI2 contains 10 wt% SnI4, the fraction of tin atoms present as Sn(IV) is (10 ÷ 626.3) ÷ [(10 ÷ 626.3) + (90 ÷ 372.5)] = about 6.2 mol%Our calculation (SnI4 626.3 g/mol, SnI2 372.5 g/mol).
Nakamura and colleagues further found that adding a reducing agent (the dihydropyrazine derivative TM-DHP) to the precursor solution made it react selectively with the SnF2 additive to form Sn(0) nanoparticles, which then captured Sn(IV). They write that they had originally expected the reducing agent to reduce Sn(IV) directly, but that the actual scavenger turned out to be the Sn(0) nanoparticles generated in solutionSourced. With this treatment they achieved a conversion efficiency of 11.5% (open-circuit voltage 0.76 V) and, for an encapsulated cell, an independently certified 11.2%Sourced.
6. Our calculation: how much oxygen oxidises 1% of the tin in 1 m²?
Let us check, as an order of magnitude, how small an amount of oxygen can drive Sn²⁺ oxidation.
- Assumption: METI's material calculates 0.34 g of tin (22.3% by mass) per m² of MASnI3 absorberSourced. From this, MASnI3 is taken as about 1.5 g/m² (0.34 ÷ 0.223)
- Assumption: formula weight of MASnI3 531.5 g/mol. 1.5 g ÷ 531.5 = 2.82 mmol of Sn
- Assumption: formally 2 Sn²⁺ + O2 → 2 Sn⁴⁺ (one oxygen molecule accepts four electrons), with all oxygen taken up used in this reaction
- Oxidising 1%, or 28.2 µmol, of Sn needs 14.1 µmol of O2 = about 0.45 mg, or about 0.32 mL at standard conditions
Result: a little over 0.3 mL of oxygen is enough to oxidise 1% of the tin in 1 m² of absorberOur calculation. Assumptions and limits: this is a formal estimate that ignores the actual oxidation products (SnI4, SnO2 and so on) and the iodine cycle of Section 4. It cannot tell us how much performance falls for a given percentage of oxidation.
In our explainer on ion migration and degradation, we calculated that about 45 mg of water would hydrate 1 m² of lead-based absorber. Tin-based perovskites add oxygen to that, and it takes effect in very small amounts. Needing a barrier against both water vapour and oxygen makes encapsulating tin-based perovskites harder still (our commentary).
7. Four layers of countermeasures: precursors, additives, crystal and interfaces
| Layer | Reported method | Reported result | Source |
|---|---|---|---|
| Precursors | Sn(0) nanoparticles formed by reaction of the reducing agent TM-DHP with SnF2 capture Sn(IV) | Films essentially free of Sn(IV), with improved PL intensity and lifetime. 11.5% (certified 11.2%) | Nakamura et al. |
| Additives | SnF2 added to CsSnI3 | Lower defect concentration and background carrier density, high photocurrent | Kumar et al. |
| Crystal | 0.08 m of a 2D layered tin perovskite mixed into 0.92 m FASnI3 | Nearly single-crystal-like, well-oriented films. Carrier density lowered by more than an order of magnitude. 9.0% in a p–i–n structure, with improved stability | Shao et al. |
| Interfaces | Choice of the underlying hole-transport layer | Film stability depends strongly on the hole-transport layer | Lanzetta et al. |
| Interfaces | A molecular layer bearing phosphonic acid groups formed at the buried (lower) interface | Uniform film growth and better hole extraction. 17.89% on a small area (certified 17.71%), 14.40% at 1 cm² | Li et al. (Nature) |
| Interfaces | A fluorinated polymer non-fullerene electron-transport layer | 16.06% at 0.04 cm² (certified 15.90%), 14.67% at 1 cm² (certified 14.51%) | Li et al. (Nature Energy) |
All Sourced (Nakamura et al. [Ref. 5], Kumar et al. [Ref. 3], Shao et al. [Ref. 4], Lanzetta et al. [Ref. 6], Li et al. [Ref. 8], Li et al. [Ref. 7]). The abstracts this article checked do not name the laboratories that performed the certification.
8. Where efficiency stands
Within what this article checked, neither NLR's (formerly NREL's) research-cell efficiency data table nor the “Solar cell efficiency tables (Version 68)” by Green and colleagues contains a row for a purely tin-based perovskite cell. The values below are therefore those reported in peer-reviewed papers (including values the papers describe as certified).
- At about 1 cm²: tin-based 14.51% (certified, Li et al.) ÷ lead-based 26.9% (efficiency tables) = about 54%, a gap of about 12.4 percentage pointsOur calculation
- Small area: tin-based 17.71% (small-area certified value, Li et al., Nature; the area is not stated in the abstract) ÷ lead-based 28.0% (0.05 cm², efficiency tables) = about 63%Our calculation
Assumptions and limits: test laboratories, areas and structures do not match exactly, so these are rough guides only. Li and colleagues (Nature) say tin-based perovskites have an ideal bandgap that supports a theoretical efficiency above 33%Sourced, which is consistent with the calculation in our explainer on bandgap and composition design (limiting efficiencies in the 33% range for 1.25 to 1.34 eV). The headroom lies not in the bandgap but in defects (oxidation state) and interfaces (our commentary).
9. A materials engineer's view (2): lead-free does not mean harmless
Babayigit and colleagues compared the environmental effects of lead-based and tin-based perovskites using zebrafish. Finding toxicity in the tin-based case through an unexpected route, acidification, they concluded that tin-based perovskites are not necessarily an ideal replacement for leadSourced. The paper also notes that tin, too, is listed as a hazardous substanceSourced.
The lesson is that “contains no lead” and “has little environmental or health impact” are separate questions (our commentary). As Section 4 showed, tin-based perovskites are also materials that readily release iodine and SnI4 when they decomposeSourced. What needs assessing is not the name of the element but which compounds are released, in what quantity and where, when a module breaks or is disposed of.
Sn–Pb mixtures, meanwhile, are used in the bottom cells of all-perovskite tandems as a way to reduce lead while obtaining a narrow bandgap (see our explainer on all-perovskite tandems). Zero lead or less lead is a choice to be made according to the application and the regulatory setting (our commentary). The handling of lead is covered in our explainer on lead and iodine.
10. Strengths, weaknesses and open issues
| Aspect | Strength (confirmed in primary sources) | Weakness or issue |
|---|---|---|
| Bandgap | Around 1.23 to 1.35 eV, supporting a theoretical efficiency above 33% (Noel et al., Hao et al., Li et al.) | The value varies with preparation method (Stoumpos et al.) |
| Structure | Sn and Pb form solid solutions at all compositions (Stoumpos et al.) | — |
| Chemistry | Sn(IV) can be removed by reduction and scavenging (Nakamura et al.) | Sn⁴⁺ doping makes it p-type (Stoumpos et al.). Cyclic SnI4–I2 degradation (Lanzetta et al.) |
| Efficiency | Certified 17.71% on a small area and 14.51% at 1 cm² (Li et al.) | About 54% of lead-based cells at 1 cm²Our calculation |
| Environment | Contains no lead | Toxicity through acidification in zebrafish (Babayigit et al.) |
Each item is Sourced (source in brackets), except “about 54%”, which is our calculation. Sorting them into strengths and weaknesses is this article's own framing.
(1) Long-term outdoor durability has not been confirmed
Li and colleagues (Nature) report that encapsulated cells retained more than 94% of their initial efficiency after 1,550 hours of continuous 1-sun illuminationSourced. However, no primary source demonstrating durability over years outdoors could be found within the scope of this articleNot yet confirmed.
(2) Track record at larger areas
Certified values reported for tin-based cells, as far as could be confirmed, go up to 1 cm². No certified efficiency at module scale could be found within the scope of this articleNot yet confirmed.
- Geometrically, tin is an almost drop-in replacement for lead. Tolerance factors with Sn are 0.91 to 1.06Our calculation
- The problem is the oxidation state. Once Sn⁴⁺ enters, the film turns p-type and metallicSourced
- There is a self-accelerating cycle: SnI4, then I2, then further oxidationSourced
- Differences in precursors invisible to XRD showed up in PL — which changes the yardstick for incoming inspectionSourced
- About 0.32 mL of oxygen oxidises 1% of the tin in 1 m²Our calculation
- The certified efficiency at 1 cm² is 14.51%, about 54% of lead-based cellsOur calculation. Lead-free and harmless are separate questions
11. Glossary
- Lead-free
- A perovskite that does not use lead on the B site. Tin is regarded as the strongest candidate substitute.
- Sn²⁺ / Sn⁴⁺
- The 2+ and 4+ ions of tin. Perovskites need the 2+ state, and oxidation to 4+ is the problem.
- p-type doping
- Holes becoming the majority carriers. In tin-based perovskites it happens unintentionally through Sn⁴⁺ and vacancies.
- Background carrier density
- The density of charge carriers present even without illumination. When high, recombination increases.
- SnF2
- The standard additive for tin-based precursor solutions. It lowers defects and carrier density.
- SnI4
- Tin(IV) iodide. It forms when tin-based perovskites oxidise and turns further into iodine, driving degradation.
- Scavenger
- A substance that selectively captures and removes impurities. Sn(0) nanoparticles capturing Sn(IV) are an example.
- 2D/3D perovskite
- A structure in which a small amount of a 2D phase, layered with large organic cations, is mixed into the ordinary 3D phase.
- PL lifetime
- The time over which emission decays after optical excitation. The more defects, the shorter it is.
- p–i–n (inverted) structure
- A cell structure stacked, from the bottom, as hole-transport layer, perovskite, electron-transport layer.
- Oxygen transmission rate
- The volume of oxygen passing through 1 m² per day (mL/m²/day and so on). A performance measure for encapsulants.
- Zebrafish
- A small fish widely used as a model organism in toxicity testing.
12. References (primary sources)
- Stoumpos, Malliakas, Kanatzidis “Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties”, Inorg. Chem. 52, 9019 (2013) https://doi.org/10.1021/ic401215x
- Noel et al. “Lead-free organic–inorganic tin halide perovskites for photovoltaic applications”, Energy Environ. Sci. 7, 3061 (2014) https://doi.org/10.1039/C4EE01076K
- Kumar et al. “Lead-Free Halide Perovskite Solar Cells with High Photocurrents Realized Through Vacancy Modulation”, Adv. Mater. 26, 7122 (2014) https://doi.org/10.1002/adma.201401991
- Shao et al. “Highly Reproducible Sn-Based Hybrid Perovskite Solar Cells with 9% Efficiency”, Adv. Energy Mater. 8, 1702019 (2018) https://doi.org/10.1002/aenm.201702019
- Nakamura et al. (Wakamiya laboratory, Institute for Chemical Research, Kyoto University, and others) “Sn(IV)-free tin perovskite films realized by in situ Sn(0) nanoparticle treatment of the precursor solution”, Nat. Commun. 11, 3008 (2020) https://doi.org/10.1038/s41467-020-16726-3
- Lanzetta et al. “Degradation mechanism of hybrid tin-based perovskite solar cells and the critical role of tin (IV) iodide”, Nat. Commun. 12, 2853 (2021) https://doi.org/10.1038/s41467-021-22864-z
- Li, He, Shen et al. “Centimetre-scale fullerene-free tin-based perovskite solar cells with a 14.51% certified efficiency”, Nat. Energy 11, 219–229 (2026; published online 5 December 2025) https://doi.org/10.1038/s41560-025-01919-1
- Li, Luo, Wang et al. “Tin-based perovskite solar cells with a homogeneous buried interface”, Nature 648, 84 (2025) https://doi.org/10.1038/s41586-025-09724-2
- Babayigit et al. “Assessing the toxicity of Pb- and Sn-based perovskite solar cells in model organism Danio rerio”, Sci. Rep. 6, 18721 (2016) https://doi.org/10.1038/srep18721
- Hao et al. “Anomalous Band Gap Behavior in Mixed Sn and Pb Perovskites Enables Broadening of Absorption Spectrum in Solar Cells”, J. Am. Chem. Soc. 136, 8094 (2014) https://doi.org/10.1021/ja5033259
- Travis et al. “On the application of the tolerance factor to inorganic and hybrid halide perovskites: a revised system”, Chem. Sci. 7, 4548 (2016) https://doi.org/10.1039/C5SC04845A
- 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
- Green et al. “Solar cell efficiency tables (Version 68)”, Joule 10, 102494 (2026) https://doi.org/10.1016/j.joule.2026.102494
13. Claim-to-source audit
| Claim in the text | Basis | Label |
|---|---|---|
| That Sn compounds oxidise readily, becoming p-type through Sn⁴⁺ doping and showing metallic conductivity. That Sn–Pb solid solutions form across the whole composition range. That properties depend strongly on the preparation method. Estimated mobilities in MASnI3 above 2,000 cm²/(V·s) for electrons and above 300 cm²/(V·s) for holes | Inorg. Chem. paper (abstract). Reference 1 https://doi.org/10.1021/ic401215x | Sourced |
| The first completely lead-free CH3NH3SnI3 cells at over 6%. An open-circuit voltage above 0.88 V from a material with a 1.23 eV bandgap. That the instability of tin's 2+ oxidation state was the biggest obstacle | Energy Environ. Sci. paper (abstract). Reference 2 https://doi.org/10.1039/C4EE01076K | Sourced |
| That CsSnI3 cells show spectral response to 950 nm. That adding SnF2 lowered defect concentration and background carrier density, giving high photocurrents | Adv. Mater. paper (abstract). Reference 3 https://doi.org/10.1002/adma.201401991 | Sourced |
| That the main reason for the low efficiency of tin-based cells is the high background carrier density due to intrinsic defects such as tin vacancies and oxidised species (Sn⁴⁺). That mixing 0.08 m of a 2D layered tin perovskite into 0.92 m FASnI3 gave well-oriented, nearly single-crystal-like films with carrier density lowered by more than an order of magnitude. 9.0% in a p–i–n structure and improved stability | Adv. Energy Mater. paper (abstract). Reference 4 https://doi.org/10.1002/aenm.201702019 | Sourced |
| That in comparing commercial SnI2 from three suppliers with purified SnI2(dmf) complex, XRD showed no difference, only the SnI2 containing about 10 wt% SnI4 could be told apart by absorption, and the source could be distinguished by PL intensity and lifetime. That PL lifetimes of 2 to 4 ns suggested residual Sn(IV). That adding 10 mol% SnF2 is a widely used method. That Sn(0) nanoparticles formed by reaction of TM-DHP with SnF2 capture Sn(IV) (the authors initially thought TM-DHP reduced it directly). 11.5% with an open-circuit voltage of 0.76 V, and a certified 11.2% for an encapsulated cell. The authors' affiliations, including the Institute for Chemical Research, Kyoto University | Nat. Commun. paper (abstract and text). Reference 5 https://doi.org/10.1038/s41467-020-16726-3 | Sourced |
| The cyclic degradation mechanism in (PEA)0.2(FA)0.8SnI3 films: oxygen-driven degradation produces SnI4, which moisture and oxygen together rapidly convert into iodine, which oxidises the perovskite further to produce more SnI4. That stability depends strongly on the underlying hole-transport layer | Nat. Commun. paper (abstract). Reference 6 https://doi.org/10.1038/s41467-021-22864-z | Sourced |
| With a fluorinated polymer non-fullerene electron-transport layer, 16.06% at 0.04 cm² (certified 15.90%) and 14.67% at 1 cm² (certified 14.51%). Over 85% retained after 550 hours of continuous 1-sun illumination | Nat. Energy paper (abstract). Reference 7 https://doi.org/10.1038/s41560-025-01919-1 | Sourced |
| With a molecular layer at the buried interface, 17.89% on a small area (certified 17.71% in reverse scan) and 14.40% at 1 cm². Encapsulated cells retaining over 94% after 1,550 hours of continuous 1-sun illumination. That tin-based perovskites have an ideal bandgap supporting a theoretical efficiency above 33%. That certified efficiencies of inverted structures had exceeded 16% | Nature paper (abstract). Reference 8 https://doi.org/10.1038/s41586-025-09724-2 | Sourced |
| That a zebrafish comparison found an unexpected toxicity route, acidification, for tin-based perovskites, which are therefore not necessarily an ideal replacement for lead. That tin, too, is listed as a hazardous substance | Sci. Rep. paper (abstract). Reference 9 https://doi.org/10.1038/srep18721 | Sourced |
| MAPbI3 at 1.55 eV and MASnI3 at 1.35 eV (the end members of the Sn–Pb series) | J. Am. Chem. Soc. paper (abstract). Reference 10 https://doi.org/10.1021/ja5033259 | Sourced |
| Six-coordinate cation radii in iodides (Sn²⁺ 0.97 Å, Pb²⁺ 1.03 Å). MA⁺ 2.16 Å, FA⁺ 2.53 Å, I⁻ 2.20 Å. That Shannon gives no radius for Sn²⁺ and that 1.15 Å had been used by other researchers | Chem. Sci. paper (text and Table 1). Reference 11 https://doi.org/10.1039/C5SC04845A | Sourced |
| That per m² of absorber, 0.34 g of tin (22.3% by mass) and 1.1 g of iodine for MASnI3, and 0.53 g of lead for MAPbI3, are calculated | METI, Next-Generation Solar Cell Strategy, page 53. Reference 12 https://www.meti.go.jp/shingikai/energy_environment/perovskite_solar_cell/pdf/20241128_1.pdf | Sourced |
| A lead-based perovskite cell of 1.017 cm² at 26.9%, and 28.0% at 0.05 cm². That the tables contain no row for a purely tin-based cell | “Solar cell efficiency tables (Version 68)”, Joule. Reference 13 https://doi.org/10.1016/j.joule.2026.102494 | Sourced |
| Tolerance factors (Sn: MA 0.97, FA 1.06, Cs 0.91; Pb: MA 0.95, FA 1.04, Cs 0.89). About 6.2 mol% Sn(IV) with 10 wt% SnI4. About 1.5 g/m² of MASnI3 and 2.82 mmol of Sn; about 0.45 mg or 0.32 mL of O2 to oxidise 1%; days for each oxygen transmission rate. Efficiency ratios of about 54% (1 cm²) and about 63% (small area), and the 12.4-point gap | Our calculation. The Cs⁺ radius of 1.88 Å (Bartel et al.'s value), the formal reaction 2Sn²⁺ + O2, and all arriving oxygen being used for oxidation are assumptions set by this article. Includes the numerical parts of Figs. 2 and 4 | Our calculation |
| Year-scale outdoor durability of tin-based cells, and certified efficiency at module scale | No primary source could be confirmed within the scope of this article; these await future reports (our note) | Not yet confirmed |
| The framing that the problem lies in the oxidation state rather than in tin itself. The three stages (bring none in, make none, let none in) and the four layers. The reading that the yardstick for incoming inspection should move to oxidation-state purity. The qualitative difference from lead-based degradation (self-acceleration). The framing that lead-free and harmless are separate questions. The reading that barriers against both water vapour and oxygen are needed. The general chemical explanation that lead favours the 2+ state and tin readily becomes 4+ | Our summary and commentary based on published content. Not views expressed by the authors of the papers | Commentary |
| That Figs. 1 to 4 are explanatory drawings, not measured data or detailed reaction mechanisms. 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 (peer-reviewed papers, a government strategy document and the efficiency tables). Because the article includes materials-design interpretations, those are marked as Commentary and kept separate from sourced fact. Year-scale outdoor durability of tin-based cells and certified efficiency at module scale are not stated, because no primary source could be confirmed. For the “certified” values in the papers, the certifying laboratories were not identified within the abstracts this article checked. 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 real measured data, raw materials or a physical product.