H/F Substitution on the Spacer Cations Leads to 1D-to-2D Increment of the Pyrrolidinium-Containing Lead Iodide Hybrid Perovskites br

Hybrid organic-inorganic perovskites (HOIPs) haveemerged as multifunctional materials with remarkable optical andelectronic properties. In particular, 2D-layered lead iodide-basedHOIPs possess great practical application potential in the photo-electricfield. In this work, we report H/F substitution-induced 1D-to-2D increment of lead iodide HOIPs. The enantiomeric HOIPs,S-andR-FPPbI3(FP = 3-fluoropyrrolidinium), were achieved bymonofluoride substitution on the spacer cations of the parent HOIP,PyPbI3(Py = pyrrolidinium), showing mirror image structuralrelationship and reversible solid-state phase transition. A 2D-layeredHOIP, (DFP)2PbI4(DFP = 3,3-difluoropyrrolidinium), wasachieved with a low band gap of 2.09 eV through difluoridesubstitution, thanks to the expansion of the Pb-I network from 1Dto 2D. This work highlights the exploration of 1D chiral and 2D-layered HOIP materials with reversible phase transitions through H/F substitution strategies.