Chinese researchers have recently developed a new perovskite-organic tandem solar cell, which has set a new world record with a steady-state photoelectric conversion efficiency of 28.04 percent, according to a study published in the journal Nature.
The solar cell, developed by the Institute of Chemistry of the Chinese Academy of Sciences (ICCAS), features a wide-bandgap perovskite top subcell that achieves the highest open-circuit voltage ever recorded for its type.
When precisely integrated with an organic bottom subcell, the tandem device's power conversion efficiency in the laboratory peaked at 28.80 percent, with a certified steady-state efficiency of 28.04 percent. The cell also demonstrated excellent operational stability, retaining 90 percent of its initial efficiency after 625 hours of continuous irradiation.
"This perovskite-organic tandem solar cell combines lightweight design, mechanical flexibility, and high efficiency," said Li Yongfang, an academician at the Chinese Academy of Sciences who led the research team.
"In addition to applications in buildings, transportation, and wearable electronics, its excellent 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 crucial," Li explained.
Emerging photovoltaic technologies, particularly perovskite and organic solar cells, have seen rapid progress in recent years. Perovskite-organic tandem solar cells maximize the utilization of the solar spectrum, with the top perovskite layer capturing visible light and the bottom organic layer absorbing near-infrared light, resulting in theoretical efficiencies far exceeding those of single-junction devices.
However, the top perovskite layer still faces a formidable challenge. To absorb sufficient sunlight, the thin film requires the simultaneous incorporation of iodine and bromine. The problem is that during the fabrication process or upon prolonged exposure to light, iodide and bromide ions tend to separate, a phenomenon known as phase separation, leading to persistent voltage drops and performance degradation.
"This phase separation has been a major obstacle that severely compromises the operational stability of the device and hinders its commercial viability," said Meng Lei, a researcher at the institute and a key member of the team.
To address this issue, the team added the molecular additive TDB to the perovskite layer. During the initial stage of perovskite film formation, TDB acts as a mediator, slowing down the rapid aggregation of bromide ions and ensuring a homogeneous distribution of iodine and bromine from the outset.
When exposed to light, TDB transforms into a new molecular structure, TAB, which then attaches to the grain boundaries of the perovskite material. "This newly formed molecule effectively suppresses halide ion migration and phase separation, transforming the material from light-resistant to light-adaptive," Meng said.
