Perovskite solar cells boosted in China lab

Chinese scientists have reported a major advancement in boosting both the efficiency and stability of perovskite solar cells, a step researchers say could help move the promising technology closer to large-scale industrial use.

A team led by You Jingbi, a professor from the Chinese Academy of Sciences' Institute of Semiconductors, said it has identified an additive that can raise the power conversion efficiency of perovskite solar cells to 27.2 percent. The devices also kept 86.3 percent of their initial efficiency after running continuously for 1,529 hours, about 63 days, at the maximum power point under standard sunlight — a sign of improved durability. The findings were published recently in the journal Science.

Perovskite solar cells have drawn global interest as a nextgeneration photovoltaic technology because they are inexpensive to produce and have achieved rapid gains in performance. Their efficiency has climbed from 3.8 percent to 26 percent in just 16 years, approaching that of conventional but costly monocrystalline silicon cells. A gap, however, remains between current performance and the theoretical limit, largely because it has been difficult to create perovskite thin films that are both high-quality and stable.

The researchers found that when a common additive — methylammonium chloride — is used, chloride tends to accumulate unevenly near the film's surface. While the additive helps slow crystal growth and form useful intermediate states, the uneven distribution disrupts the smooth flow of electric charges through the material.

To solve this, the team introduced alkali metal oxalates during film growth. The compounds help bind potassium ions with chloride ions, preventing chlorine from migrating randomly and ensuring it is spread evenly throughout the film. This produces perovskite layers with a carrier lifetime of up to 20 microseconds — an indicator of how long charges can move before recombining — and a reduced defect density of 1013per cubic centimeter.

The study said further work is needed to reduce defects at the buried interface, a deeper layer where materials meet, in order to raise efficiency and maintain long-term stability. Continued progress, the researchers said, could accelerate the path toward commercial deployment of perovskite solar cells.

limenghan@chinadaily.com.cn