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The new strategy pushed the uniform crystallization window past 100 seconds.
A new methylammonium-free (MA-free) perovskite solar module achieved a power conversion efficiency of 22.7%.
The modules retained nearly 98% of the original efficiency during the standard stability tests.
Researchers paired slot-die coating with a new crystallization strategy to improve film formation and durability.
Chinese researchers have developed a new methylammonium-free (MA-free) perovskite solar module that achieved a 22.7 percent power conversion efficiency. In a stability test, the module retained nearly 98 percent of the original efficiency.
The Chinese Academy of Sciences (CAS) and Dalian Jiaotong University created a process to manufacture uniform perovskite solar modules using slot-die coating under normal ambient conditions.
“We developed a reliable fabrication process for uniform, high-efficiency, methylammonium-free perovskite solar modules using slot-die coating under ambient conditions,” said the study author Zhihua Zhang.
Perovskite solar cells are widely used in photovoltaic applications because of high efficiency and low manufacturing costs.
However, many high-performance devices rely on methylammonium (MA), which degrades easily under heat. Degraded MA releases volatile compounds that damage the perovskite crystal structure, increasing defects and reducing the cell’s efficiency over time.
To overcome this limitation, the researchers designed an MA-free perovskite material and paired it with a new crystallization strategy that improves film formation during manufacturing.
The team said that slot-die coating is well suited for large-scale production. The technique uses materials efficiently and can be integrated into continuous roll-to-roll manufacturing lines.
Slot-die coating is different from the spin-coating process commonly used in laboratories. It spreads the perovskite solution across larger surfaces and makes it more suitable for commercial-scale production. However, producing uniform films over large areas remains a major challenge because the perovskite crystals must form evenly during processing.
Researchers addressed this hurdle by introducing a combined additive strategy using rubidium thiocyanate (RbSCN) and formamidinium thiocyanate (FASCN).
The additives work together to guide crystal growth and promote the conversion of the material from a non-photoactive crystal phase, known as the δ-phase, into the photoactive α-phase that generates electricity. At the same time, they suppress the formation of unwanted secondary phases that can reduce device performance.
According to the researchers, lowering the energy barrier between these two crystal structures makes the crystallization process more predictable and produces films with fewer defects.
“Rather than imposing tighter constraints on process control, this work makes the crystallization process itself more tolerant of processing variability,” Zhang said.
The team reported that the additive combination expanded the processing window for uniform crystallization to more than 100 seconds. This allowed dense, high-quality perovskite films to form with larger crystal grains, lower residual stress, and a more uniform composition throughout the film.
Adopting the new coating methods improved performance for both laboratory cells and larger solar modules.
The researchers reported a power conversion efficiency of 26.16 percent for small-area solar cells. A larger module with an active area of 54.8 square centimeters achieved 22.70 percent efficiency, compared with 15.8 percent for a reference module produced without the additive strategy.
The new design also demonstrated improved durability.
According to the study, during the stability tests where the device’s temperature was raised to 149°F, unencapsulated solar modules retained 97.76 percent of their original efficiency. The efficiency was maintained even after 1,300 hours of continuous operation, which is equivalent to over 54 days of uninterrupted use under the heat a solar panel can experience in strong sunlight.
However, under the same conditions, the control devices without the additive strategy retained only 65.86 percent of their initial efficiency.
A wider processing window and improved crystal control could make slot-die coating viable for mass-producing perovskite solar modules, researchers said.
The findings were published recently in the journal Advanced Materials.
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