BEIJING, July 16 (Xinhua) -- Chinese researchers have recently developed a novel perovskite-organic tandem solar cell that has set a new world record of 28.04 percent for steady-state photoelectric conversion efficiency, according to a study published on Monday in the journal Nature.
The cell, developed by the Institute of Chemistry of the Chinese Academy of Sciences (CAS), features a wide-bandgap perovskite top subcell that has achieved the highest open-circuit voltage ever recorded for its type.
When precisely integrated with an organic bottom subcell, the laboratory power conversion efficiency of the tandem device peaked at 28.80 percent, with a certified steady-state efficiency of 28.04 percent. The cell also demonstrated remarkable operational stability, retaining 90 percent of its initial efficiency after 625 hours of continuous illumination.
"This perovskite-organic tandem solar cell combines lightweight design, mechanical flexibility and high efficiency," said Li Yongfang, a CAS academician who led the research team.
"Beyond applications in buildings, transportation and wearable electronics, its exceptional power-to-weight ratio makes it a promising candidate for future space missions, including satellites and space stations, where lighter and more efficient energy sources are critical," Li said.
Emerging photovoltaic technologies, particularly perovskite and organic solar cells, have advanced rapidly in recent years. Perovskite-organic tandem solar cells maximize solar spectrum utilization: the perovskite top layer captures visible light while the organic bottom layer absorbs near-infrared light, delivering a theoretical efficiency far surpassing that of single-junction devices.
However, a persistent challenge has plagued the top perovskite layer. To absorb sufficient sunlight, the thin film requires the simultaneous incorporation of iodine and bromine. Yet during fabrication or under prolonged illumination, iodide and bromide ions tend to segregate -- a phenomenon known as phase separation -- causing a continuous drop in voltage and performance degradation.
"This phase separation has been a critical bottleneck, severely undermining the device's operational stability and hindering its commercial viability," said Meng Lei, a researcher at the institute and a key member of the team.
To address this problem, the team introduced an additive molecule, TDB, into the perovskite film. During the initial formation of the perovskite film, TDB acts as a mediator, slowing the swift aggregation of bromide ions and ensuring a homogeneous distribution of iodine and bromine from the outset.
Upon exposure to light, TDB transforms into a new molecular structure, TAB, which anchors at the grain boundaries of the perovskite material. "This newly formed molecule effectively suppresses halide ion migration and phase separation, a transformation from being light-averse to light-adaptive," Meng said. ■
