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

Hybrid organic-inorganic perovskites (HOIPs) have emerged as multifunctional materials with remarkable optical and electronic properties. In particular, 2D-layered lead iodide-based HOIPs possess great practical application potential in the photoelectric field. In this work, we report H/F substitution-induced 1D-to-2D increment of lead iodide HOIPs. The enantiomeric HOIPs, S - and R -FPPbI 3 (FP = 3-fluoropyrrolidinium), were achieved by monofluoride substitution on the spacer cations of the parent HOIP, PyPbI 3 (Py = pyrrolidinium), showing mirror image structural relationship and reversible solid-state phase transition. A 2D-layered HOIP, (DFP) 2 PbI 4 (DFP = 3,3-difluoropyrrolidinium), was achieved with a low band gap of 2.09 eV through difluoride substitution, thanks to the expansion of the Pb-I network from 1D to 2D. This work highlights the exploration of 1D chiral and 2D-layered HOIP materials with reversible phase transitions through H/F substitution strategies.