Perovskite solar cells have spent a decade proving they can be efficient in the laboratory and a shorter, harder period proving they can be coated evenly at the size a factory needs. The gap is mostly a crystallization problem: a wet film of perovskite ink has to dry into a uniform crystal over a large area before the chemistry runs away from it, and the compositions that survive longest in a finished device are the ones hardest to crystallize evenly. A team led by Yang Dong at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences, working with Dalian Jiaotong University, reports in Advanced Materials that two additives used together — formamidinium thiocyanate (FASCN) and rubidium thiocyanate (RbSCN) — widen the window in which that crystallization can be controlled during ambient-air slot-die coating, from a window too narrow to work with to more than 100 seconds. Small-area cells reach 26.16% power conversion efficiency, and a module with a 54.80 cm² active area reaches 22.70%, against 15.8% for the control module made without the additives.
The paper, first-authored by Lianjie Duan, is a process result first and an efficiency result second: the mechanism is what a manufacturer can actually use. The stability data are strong and clearly stated. The certification status of the efficiency figures is not stated in the material consulted, and no roll-to-roll speed, outdoor exposure, or damp-heat result accompanies the paper — limits this article states plainly rather than smoothing over.
The problem: a stable composition that refuses to crystallize evenly
The perovskite in this work is methylammonium-free: FAₓCs₁₋ₓPbI₃, a formamidinium–cesium lead triiodide. Dropping methylammonium is a durability choice — methylammonium is volatile, and its tendency to leave the crystal under heat is one reason early perovskite devices degraded — but the FA–Cs composition pays for that stability during fabrication. Its intrinsic crystallization is slower, and its tendency toward phase segregation is stronger, which makes wet-film control and uniform crystallization during ambient-air coating harder.
The phase problem is the sharp end of that difficulty. Formamidinium lead iodide wants to crystallize into the photoactive α-phase, the black phase that absorbs sunlight and makes current. Left to itself, it readily falls into the non-photoactive δ-phase instead, a yellow phase that contributes nothing to a solar cell. The δ-to-α transition has a narrow processing window, and in a large-area wet film the window is narrower still: solvent evaporates at different rates in different places, local composition drifts, and some regions crystallize into the wrong phase or into grains of uneven size, eating module efficiency in ways that get worse as the coated area grows.
Slot-die coating is the deposition method the team is trying to make work. A slot-die head meters ink through a narrow slit onto a moving substrate, laying down a wet film of controlled thickness with high material utilization and, in principle, direct compatibility with continuous roll-to-roll processing. It is the coating method most often named as perovskite’s route to gigawatt-scale manufacturing. But slot-die coating a perovskite ink in ambient air gives the film a finite time to crystallize before the solvent is gone. If that time is too short, or too variable across the film, the film is defective before it is a device. The processing window — the span of time over which uniform crystallization can still be achieved — is the quantity this paper sets out to expand.
The fix: one additive to nucleate, one to hold the phase
The team’s answer is a pair of thiocyanate additives with deliberately complementary roles, and the complementarity is the point. FASCN and RbSCN do not do the same job twice as well; they do two different jobs that the crystallization process needs done at the same time.
FASCN governs nucleation and growth. According to the trade coverage of the paper, it promotes nucleation induced by vacuum-flash treatment — the step in which a brief vacuum exposure rapidly extracts solvent from the wet film and triggers the perovskite to nucleate — and then promotes the subsequent crystal growth. The thiocyanate anion (SCN⁻) is doing work the field has seen before: thiocyanate additives have been reported to passivate defects and promote uniform crystal growth, and a related thiocyanate, methylammonium thiocyanate, has been used in ambient slot-die work to promote controlled crystallization. Here the formamidinium variant plays the nucleation role, seeding the film in an ordered way at the moment the vacuum flash forces it to crystallize.
RbSCN governs phase stability. The rubidium ion, Rb⁺, occupies the A site of the perovskite lattice — the site normally held by formamidinium or cesium — and in doing so relaxes lattice strain and lowers the activation energy for forming the photoactive α-FAPbI₃ phase, thereby suppressing the formation of the non-photoactive δ-FAPbI₃ phase. The effect is thermodynamic as well as kinetic: by making the right phase easier to form and the wrong phase harder to reach, RbSCN shifts the balance of the crystallization itself, not merely its speed.
Together, the two additives extend the processing window for uniform perovskite crystallization to more than 100 seconds — long enough, in principle, for a wet film to be laid down, flashed, and crystallized uniformly across a large area without the process racing the chemistry, and long enough to be compatible with the dwell times of a continuous coating line. The films that result, as reported, have a dense microstructure, large grains, a uniform vertical compositional gradient, and reduced residual stress — fewer pinholes and shunt paths, fewer grain boundaries where charge recombines, and a film less likely to crack or delaminate as it ages.
The device numbers, handled in order
The small-area cells reach 26.16% power conversion efficiency — a strong number for a methylammonium-free composition coated by slot-die in ambient air. But three qualifications travel with it. The aperture area of the small-area cells is not stated in the material consulted. The device stack — the transport layers, the electrodes, the cell architecture — is not stated either. And no certifying laboratory is named; it is the paper’s reported value, quoted here as such rather than as a certified figure.
The module result is the one that carries the paper’s claim. A large-area module with a 54.80 cm² active area reaches 22.70% efficiency, against 15.8% for the control module fabricated the same way without the additives — a 6.9-percentage-point improvement on the same area and the same process, which is the honest comparison, since the control isolates the additives’ contribution from everything else about the fabrication line. A module holding 22.70% at 54.80 cm² is a genuinely strong large-area result: most scaled-up perovskite modules have lingered below 20%. But the area matters: 54.80 cm² is a large-area demonstration, not a full-module demonstration. The UNSW–UtmoLight submodule covered on October 31 reached 23.5% at a 676 cm² aperture, and the Nanjing–Renshine rigid module reached a certified 24.0% at an 810 cm² aperture — roughly twelve times the Dalian area. Efficiency at 55 cm² is a different, easier test than efficiency at 700 cm².
Stability: the number that outruns the efficiency
The stability data are where this paper separates itself from most slot-die reports, and they deserve to be read in full. Unencapsulated devices retained 97.76% of their initial efficiency after 1,300 hours of continuous maximum-power-point tracking under AM 1.5G illumination at 65 °C; by comparison, control devices retained only 65.86% under the same conditions.
Two things make that combination worth taking seriously. First, the test is operational, not storage: maximum-power-point tracking under continuous illumination at 65 °C is a device working at its operating point, under light and heat, for 1,300 hours — more than seven weeks. Retention of 97.76% under those conditions is a strong result for any perovskite device, and the 32-percentage-point gap to the control is the additives’ signature: the same film chemistry that crystallizes more uniformly also degrades more slowly. Second, the devices were unencapsulated — no barrier layer protecting them from the atmosphere — so the stability result cannot be credited to packaging.
The limits are that the test is one stress axis at a time in the sense that matters most to buyers: heat plus illumination, but no humidity. The 1,300-hour test ran at 65 °C under light, with no relative-humidity figure stated in the material consulted — and humidity is the stressor that has historically been perovskites’ hardest failure mode. The Southeast–Soochow flexible modules covered on November 5 were tested under ISOS-L-3 at 85 °C and 65% relative humidity and passed all sequences of IEC TS 63163. The Dalian result has no damp-heat (85 °C/85% relative humidity) data and no IEC sequence stated in the material consulted, so nothing here speaks to moisture-driven degradation. The stability-test devices’ starting efficiency is also not stated, so the 97.76% retention cannot be tied to a specific initial efficiency.
Where it sits in the scaling arc
Place this result beside the other perovskite scaling stories of the last two weeks, and the pattern sharpens. October and early November have produced five distinct answers to the same question — can perovskite hold its efficiency as it grows? The Northwestern–DGIST result of October 27 was a defect-passivation answer at 0.049 cm², reaching 27.4%. The UNSW–UtmoLight submodule of October 31 was a process-simplification answer at 676 cm², reaching 23.5% without nickel oxide. The Microquanta–Zhejiang mini-module of November 2 was a thermal-history answer at 19.48 cm², reaching a certified 23.9% by preserving fill factor. The Southeast–Soochow result of November 5 was the flexible answer: a decoupling molecule in the printing ink, holding above 20% to a 750 cm² device area with a certified stability pass. The Dalian result is the ambient-coating answer: a two-additive strategy that makes slot-die coating work in air, on a methylammonium-free composition, holding 22.70% at 54.80 cm² with strong operational stability.
What this is not: no roll-to-roll line, no certificate, no damp heat
The honest limits are specific, and they are the limits a reader deciding whether this matters should carry.
First, no roll-to-roll demonstration accompanies the paper in the material consulted. Slot-die coating is compatible with continuous roll-to-roll processing as a general property of the technique — the trade coverage says so, and the review literature agrees — but compatibility is not a demonstration. The paper’s evidence for factory readiness is the processing window: more than 100 seconds of uniform crystallization, in ambient air, on a slot-die coater. Whether that window holds at roll-to-roll speeds, with a moving web and uniform additive dosing across meters of foil, is untested here.
Second, the efficiency figures carry no certification in the material consulted. Neither the 26.16% small-area figure nor the 22.70% module figure is described as certified, and no certifying laboratory is named — a thinner certification trail than the Southeast–Soochow paper, which reports certified values, or the Nanjing–Renshine module, which names TÜV SÜD.
Third, the stability evidence covers one stress axis — heat plus illumination — and not humidity, thermal cycling, or outdoor exposure. The devices were unencapsulated, which strengthens the result, but the test ran at 65 °C with no humidity figure stated, and no damp-heat or IEC sequence appears in the material consulted.
Fourth, the demonstration is one composition family — FAₓCs₁₋ₓPbI₃ — and, as far as the material consulted states, one coating setup. Whether the same additive pair widens the window on other compositions is untested here, and no cost, yield, or throughput data accompany the paper, so the economic case for adding two thiocyanates to a production ink is untested as well.
What to watch
Three things, in order of how quickly they could change the assessment. First, documentation: a published certificate naming the certifying laboratory for the 26.16% cell and the 22.70% module, and a fuller device description — the small-area aperture, the stack, the module’s total area against its 54.80 cm² active area — would let the figures be quoted without footnotes. Second, a damp-heat result: an 85 °C/85% relative-humidity test, or an IEC 61215 sequence, would convert the stability claim into the kind of durability evidence a buyer or insurer asks about. Third, a continuous-coating demonstration: a roll-to-roll run would test whether a 100-second processing window survives the transition from a laboratory slot-die coater to a moving web, where uniform dosing of two additives across meters of foil is its own engineering problem.
The bottom line
A Dalian Institute of Chemical Physics team, with Dalian Jiaotong University, has given slot-die perovskite coating a chemical diagnosis precise enough to act on — a methylammonium-free film whose slow crystallization and phase-segregation tendency leave too narrow a window for uniform coating in ambient air — and a fix small enough to ride in the coating ink: two thiocyanate additives, FASCN to drive nucleation under vacuum-flash treatment and RbSCN to hold the photoactive α-phase by relaxing lattice strain, stretching the uniform-crystallization window past 100 seconds. The small-area cells reach 26.16%, the 54.80 cm² module reaches 22.70% against a 15.8% control, and unencapsulated devices retain 97.76% of their efficiency after 1,300 hours of maximum-power-point tracking at 65 °C under illumination, against 65.86% for the control.
It is a November paper, not a factory demonstration: no roll-to-roll line has run the process, no certificate accompanies the efficiency figures in the material consulted, and no damp-heat test has been reported. Frame it as the strongest ambient slot-die result reported to date on a methylammonium-free composition, achieved by giving the film two additives with two different jobs — and let the certificate, the damp-heat test, and the moving web decide whether a wider processing window becomes a production line.
No investment recommendation is made or implied anywhere in this article.
Sources and further reading
- Phys.org (November 5, 2026), “Researchers develop synergistic additives for scalable slot-die-coated perovskite photovoltaics” — the trade coverage this article works from, and the source for the team leadership (Yang Dong, DICP/CAS, with Dalian Jiaotong University), the additive pair and their complementary roles (FASCN promoting vacuum-flash-induced nucleation and crystal growth; RbSCN stabilizing the photoactive phase, Rb⁺ occupying the A site, relaxing lattice strain, lowering the activation energy for α-FAPbI₃ formation and suppressing δ-FAPbI₃), the processing window of more than 100 seconds, the film properties (dense microstructure, large grains, uniform vertical compositional gradient, reduced residual stress), the device figures (26.16% small-area cells; 22.70% module at 54.80 cm² active area against a 15.8% control), and the stability result (unencapsulated devices retaining 97.76% after 1,300 hours of continuous maximum-power-point tracking under AM 1.5G illumination at 65 °C, against 65.86% for the control).
- Duan, L., et al. “Processing Window Expansion Enables Uniform Crystallization in Scalable Ambient-Fabricated Perovskite Photovoltaics.” Advanced Materials (2026). DOI: 10.1002/adma.75520 — the primary source for the paper title, author list, and DOI. The full text was not directly readable through the sources available for this article (the publisher’s page returned an access error), so device figures, stability data, and mechanism details are reported from the trade coverage of the paper, as stated above.
- Excitonic.com, “Flexible Perovskites Stop Fighting Themselves: 26.86% Certified, Modules Hold Above 20% at 900 cm²” (November 5, 2026) — the paired scaling story: Southeast–Soochow decoupled co-deposition, certified 26.86% flexible cell, 20.15% at 750 cm² device area, ISOS-L-3 at 85 °C and 65% relative humidity with a TÜV SÜD-certified IEC TS 63163 pass; and “Two Defect-Fixers That Don’t Fight Each Other Take Perovskite Cells to 27.4%” (October 27, 2026) — the Northwestern–DGIST orthogonal passivation result, 27.4% champion on a 0.049 cm² aperture, 1,030 hours to T90 under ISOS-L-3 at 85 °C; and “Perovskite’s Scaling Test, Passed at 30 cm: UNSW and UtmoLight Hit 23.5% Without Nickel Oxide” (October 31, 2026) — 23.5% at 676 cm² aperture; and “A 15-Second Chill Holds the Fill Factor: Perovskite Mini-Modules Hit 23.9% Certified” (November 2, 2026) — the Microquanta–Zhejiang cryo result and the Nanjing–Renshine rigid-module context (certified 24.0% at 810 cm² aperture, TÜV SÜD, IEC 61215 pass).
A note on sourcing: the full body text of the Duan paper was not directly readable through the sources available for this article; the publisher’s page returned an access error and was not retried. All device figures, stability data, and mechanism details are therefore reported from the Phys.org coverage of the paper, which is dated November 5, 2026 and cites the paper by DOI. No small-area aperture, device stack, module total area, certifying laboratory, coating humidity, or roll-to-roll demonstration is stated, because none appears in the material consulted. No outdoor-exposure, cost, yield, or damp-heat data are stated, because none appears in the material consulted. Background on slot-die coating, thiocyanate additives, and the δ-to-α phase transition in FA–Cs perovskites is drawn from the standard perovskite literature, including the Nano-Micro Letters review of slot-die-coated perovskite cells and modules (2026).