Osaka Robot Platform Guides Perovskite Cell to 24.4% Efficiency

• University of Osaka researchers built a robot platform that coats perovskite films and records how they form, down to a few milliseconds.
• Machine learning picked the antisolvent droplet speed; a hand-built cell made with it reached 24.4%, a lab figure that is not certified.
• The record for a single-junction perovskite cell on the U.S. national laboratory chart is 28.0%, 3.6 points higher.

Researchers at the University of Osaka have built a robot-assisted platform that coats perovskite films while recording how they form, and a solar cell made with settings it helped choose reached 24.4% efficiency. The work appeared in ACS Nano on Oct. 27.

The system runs each coating step inside an environment-controlled chamber. Cameras catch changes in film color on a subsecond scale and resolve the motion and impact of antisolvent droplets within a few milliseconds, the university said in a statement.

Machine-learning regression combined with SHAP analysis then ranked which conditions mattered most. Guided by that, the team tuned the antisolvent droplet velocity. The 24.4% device was made by hand, and the paper says it matched results from the automated system. It is a lab measurement reported by the authors, not an independently certified result.

The study in numbers

• 24.4% power conversion efficiency for the best cell, built manually with the tuned droplet velocity; lab-reported, not certified.
• 2 automated systems: one coats and records each film, the other grades it by microwave conductivity and photoluminescence.
• 4 environmental variables recorded during each run: temperature, humidity, oxygen and volatile organic compounds.
• 2 perovskite recipes compared; the two-cation and three-cation mixes reacted very differently to temperature during annealing.
• 28.0% is the certified record for a single-junction perovskite cell, set by Hainan University in February 2026 on a 0.051-cm² device, per National Laboratory of the Rockies data.
• 3.6 percentage points separate the Osaka cell from that record, putting it at 87% of the record value (list.solar calculation).

Perovskite layers start as a liquid that dries and crystallizes, and small swings in temperature or humidity change both the film and the finished cell. Many recent perovskite results in list.solar's technology section come from new materials or interface layers. The Osaka group went after the coating process itself.

"We want to move beyond trial and error by measuring what happens to the film while it is actually forming," lead author Ryosuke Kado said. Senior author Akinori Saeki added: "The advantage of automation is that we can collect much richer information than would be practical by hand."

Neither the abstract nor the release gives the cell area or stability data. Modules sit in a separate category from record cells; in August, list.solar reported on certified large-area perovskite modules made in China.