SKKU Team Cuts Perovskite Defects to Record Lows, Runs Solar Cell as LED

A perovskite solar cell built at Sungkyunkwan University has reached a certified 25.9% power conversion efficiency, and the same device, without structural changes, also worked as an LED with 26.1% external quantum efficiency. The results were published in Science on October 8, 2026, by a team led by Professor Seong Sik Shin of the SKKU Advanced Institute of Nanotechnology (SAINT), with the Korea Research Institute of Chemical Technology (KRICT), the University of California, San Diego, and Princeton University.

The numbers behind the efficiency figure matter more than the efficiency itself. The films show a charge-carrier lifetime of roughly 295 μs, among the longest ever reported for perovskites. The surface recombination velocity fell to 0.3 cm/s, the lowest value on record for lead halide perovskites and comparable to the best passivated silicon. Solution processing, long treated as the cheap-but-grainy cousin of vacuum deposition, has now produced surfaces as clean as the incumbent's.

Why were the defects there in the first place?

Perovskites are attractive because they are cheap to make and simple to process. That same simplicity is their defect problem. When a liquid precursor solution solidifies into a film, microscopic crystal grains form and merge, leaving defects at grain boundaries and surfaces. Those defects trap or destroy photo-generated carriers, cutting both performance and operational lifetime.

The team's fix draws on the eutectic phenomenon, in which a mixture melts well below the melting point of its individual components. The researchers combined methylammonium chloride (MACl) and a zinc halide (ZnX₂), two materials with relatively high individual melting temperatures. Heated gently to around 100°C, the mixture at the grain boundaries turned into a thin liquid layer.

Liquid-state transport did the repair work. Atoms diffuse roughly 10,000 times faster in liquid than in solid, so small grains merged rapidly into larger, cleaner crystals. The MACl, having served its purpose as a growth facilitator, evaporated during thermal annealing, while the remaining zinc segregated to the grain boundaries and suppressed defects there.

What does the record actually consist of?

The fabricated solar cells delivered a power conversion efficiency of 26.5%, with the certified figure at 25.9%. The open-circuit voltage reached 1.208 V, a certified record for solar cells using the same n-i-p architecture. The identical device architecture then ran as an LED at 26.1% external quantum efficiency, absorbing light to generate power in one mode and emitting it in the other.

Dr. Seongsik Nam of SKKU, co-first author of the study, said: "We reduced the surface recombination velocity to 0.3 cm/s, the lowest reported for perovskite thin films, demonstrating that solution processing can achieve surface quality comparable to that of silicon. As we have also demonstrated strong performance over large areas, we expect this technology to help accelerate the commercialization of perovskite solar cells."

Does the process need exotic equipment?

No, and that is the commercial point. Professor Shin said: "This study is the world's first to develop a crystal-growth method based on a volatile eutectic mixture that fundamentally reduces defects in perovskites. Beyond realizing both a highly efficient solar cell and an LED within a single device architecture, the process requires no expensive specialized equipment."

He added: "We expect this approach to find broad applications not only in various optoelectronic devices, including displays and photodetectors, but also across the wider field of materials science."

The study was jointly led by corresponding authors Professor Seong Sik Shin of SKKU, Professor David P. Fenning of UC San Diego, and Professor Dane W. deQuilettes of Princeton. Co-first authors were Dr. Seongsik Nam of SKKU, Dr. Jason J. Yoo of KRICT, and Dr. Connor J. Dolan of UC San Diego. Funding came from the Ministry of Science and ICT and the National Research Foundation of Korea, through the Excellent Young Researcher Program and the National Strategic Technology Materials Development Program.

For perovskite manufacturing, a defect-healing step that runs at 100°C on standard equipment removes one of the format's familiar excuses. Whether certified 25.9% efficiency survives the scale-up to production lines will decide how quickly that advantage converts into commercial capacity.