Chinese researchers develop perovskite-organic solar cell with record efficiency

Researchers from the Institute of Chemistry, Chinese Academy of Sciences (ICCAS) have developed a new perovskite-organic tandem solar cell that has achieved a certified steady-state photoelectric conversion efficiency of 28.04 percent, setting a new world record. The cell features a wide-bandgap perovskite upper subcell that achieves the highest open-circuit voltage ever recorded for its type. When precisely integrated with an organic lower subcell, the tandem device reached a peak laboratory power conversion efficiency of 28.80 percent. It also demonstrated exceptional operational stability, maintaining 90 percent of its initial efficiency after 625 hours of continuous illumination. Li Yongfang, an academician at the Chinese Academy of Sciences who led the research team, stated that the perovskite-organic tandem solar cell combines lightweight design, mechanical flexibility, and high efficiency. He noted that beyond applications in buildings, transportation, and wearable electronics, its outstanding 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. Emerging photovoltaic technologies, particularly perovskite and organic solar cells, have advanced rapidly in recent years. Perovskite-organic tandem cells maximise solar spectrum utilisation, with the upper perovskite layer capturing visible light and the lower organic layer absorbing near-infrared light, yielding theoretical efficiencies far exceeding single-junction devices. However, the perovskite top layer has faced persistent challenges. To absorb sufficient sunlight, the thin film must incorporate both iodine and bromine. During fabrication or prolonged light exposure, iodide and bromide ions tend to separate, a phenomenon known as phase segregation, leading to continuous voltage loss and performance degradation. Meng Lei, a researcher at the institute and a key team member, explained that phase segregation has been a major bottleneck, severely disrupting device operational stability and hindering commercial feasibility. To address this, the team introduced an additive molecule called TDB into the perovskite layer. During the initial film formation stage, TDB acts as a mediator, slowing the rapid aggregation of bromide ions and ensuring a homogeneous distribution of iodine and bromine from the outset. Upon light exposure, TDB transforms into a new molecular structure, TAB, which then anchors to the grain boundaries of the perovskite material. Meng noted that this newly formed molecule effectively suppresses halide ion migration and phase segregation, representing a transformation from being light-intolerant to light-adaptive.