Highly efficient and stable perovskite solar cells via a multifunctional hole transporting material

Context & scaleThe hole-transporting material (HTM) is a key component in perovskite solar cells (PSCs), as it helps transfer charges and reduces unwanted interactions between the perovskite layer and the electrode. A new organic HTM called T2 has been developed, which outperforms the commonly used spiro-OMeTAD. T2 has unique electronic, structural, and chemical properties that enhance its ability to extract holes and reduce charge recombination at the interface. When used with thermally evaporated perovskite films, T2 achieved power conversion efficiencies of 26.41%. In addition, strong interactions of T2 with the adjacent layers help prevent ion migration, boosting PSC stability. These results, along with its simple and low-cost production process, make T2 a promising candidate for the future widespread use of PSCs.Highlights•A low-cost, high-performance multifunctional HTM for perovskite solar cells•Vacuum-evaporated perovskite solar cells with PCE of over 26%•Inhibition of ion migration by HTM leads to more stable perovskite solar cellsSummaryThe hole-transporting material (HTM) plays a crucial role in the performance and stability of perovskite solar cells (PSCs). Ideally, it facilitates lossless charge transfer and suppresses charge recombination and ion migration between the perovskite and electrode. These bulk and interface functionalities require tailored electronic, structural, and chemical properties of the material and film. Here, we report a multifunctional organic HTM T2 based on a thiomethyl-substituted fluorene arm and spiro-[fluorene-9,9′-xanthene] core exhibiting enhanced hole extraction and reduced interface recombination compared with the benchmark HTM spiro-OMeTAD. T2 exhibits strong interactions with adjacent layers, which effectively inhibit interlayer ion migration, leading to enhanced stability. In combination with thermally evaporated perovskite films, power conversion efficiencies of 26.41% (26.21% certified) and 24.88% (certified) have been achieved for 0.1 and 1.0 cm2 PSCs. The excellent performance together with a scalable and low-cost synthesis laid a solid foundation for the future large-scale application of PSCs.Graphical abstract