Triaxial Perovskite Composite Fibers Spinning the Way to Flexible Solar Cells

Hybrid halide perovskites have made significant progress in achievably high photoconversion efficiencies (>25%) and stability as a function of their chemical engineering realized by isomorphous substitution at all three sites in AMX₃ composition. Whereas the focus of current research lies on planar (2D) devices, this work brings forth an innovative structural engineering concept based on direct electrospinning of the three major perovskite solar cell components, namely, photoabsorber, hole, and electron transport materials, as continuous single triaxial fibers of μm radial dimensions (<5 μm). These perovskite fibers lay the foundation of materials engineering for fabricating tiny solar cells, which can either be woven into fabrics or incorporated as single fibers to power wearables and a variety of devices or sensors, forming the internet of things. The structures of the here presented coaxial CuSCN/MAPbI₃ (MA = CH₃NH₃ ⁺) and triaxial CuSCN/MAPbI₃/ZnO‐Zn(OAc)₂ composite fibers are verified by X‐ray diffraction data and electron microscopy coupled with energy dispersive spectroscopy and cross‐sectional analysis with focused ion beam. This work demonstrates the first report where the entire photovoltaic (PV) device and material configuration are achieved as concentric axial cables fabricated via single‐step electrospinning process.