UC San Diego Engineers Use Temporary Liquid Phase to Improve Perovskite Solar Cells

Engineers co-led by the University of California San Diego have devised a crystallization technique that produces larger, more uniform halide perovskite films with fewer defect sites, improving both efficiency and stability in solar cells and light-emitting diodes.

In laboratory testing, optoelectronic devices fabricated with the technique achieved energy conversion efficiencies between 24% and 26%, placing them near the top of reported performance benchmarks for perovskite-based hardware. The resulting solar cells retained most of their initial power conversion efficiency after running continuously for eight weeks under simulated sunlight, according to research reported by TechXplore (https://techxplore.com/news/2026-10-temporary-liquid-perovskite-solar-cells.html).

Halide perovskites attract significant industry interest because they can be solution-processed into thin films at lower temperatures and costs than conventional silicon wafers. However, standard solution-deposited films form polycrystalline layers with numerous grain boundaries. These interfaces harbor structural and electronic defects that capture charge carriers, degrading device efficiency—a loss mechanism that becomes more pronounced as active surface areas expand to commercial panel scales.

To address this constraint, researchers led by David Fenning at the UC San Diego Jacobs School of Engineering collaborated with teams from Princeton University and South Korea's Sungkyunkwan University. The team added two salts—zinc bromide and methylammonium chloride—to the perovskite precursor solution. Under heating, the additives formed a low-melting eutectic mixture that acted as a temporary liquid layer around developing crystal grains.

This transient liquid phase gave crystal structures the mobility needed to reorganize into ordered configurations at a constant processing temperature. As thermal treatment progressed, the methylammonium chloride evaporated, while residual zinc concentrated along crystal grain boundaries to neutralize electronic defects. X-ray imaging confirmed that the material followed a reversible solid-liquid-solid transition during growth.

"We introduce a new way of tuning the growth of halide perovskites by developing an additive mixture that actively evolves during crystallization," said co-first author Connor Dolan, a doctoral alumnus from Fenning's laboratory. "What's even cooler is that the end product removes performance-limiting defects at the edges of the crystalline grains."

Dolan noted that the treated perovskite films demonstrated the longest electron-hole pair lifetimes recorded to date for any direct-bandgap semiconductor, indicating reduced recombination losses. The study, published in Science with lead author Jason J. Yoo, found the mechanism was effective across multiple perovskite chemical formulations. The researchers are now investigating alternative eutectic chemistries to further refine crystal growth for scalable manufacturing.