Melt‐Processable Chiral 1D Hybrid Metal Halides With Tunable Excitonic and Circular Dichroism Properties

Abstract

ABSTRACT Chiral organic–inorganic metal halides (OIMHs) are promising semiconductors for chiroptoelectronic applications, yet scalable solvent‐free melt processing remains challenging because most systems decompose before melting. Here, we report a chiral one‐dimensional (1D) OIMH, S/R ‐MBPPbI 3 , rationally designed to combine a low melting point (T m = 160°C) with high thermal stability (> 290°C), enabling a wide melt‐processing window. Upon heating, S/R ‐MBPPbI 3 first undergoes a reversible solid‐solid phase transition at 135°C, in which the organic cations become disordered while the inorganic 1D [PbI 3 ] − chains remain structurally intact. These data indicate an order‐disorder transition in which the organic MBP + sublattice becomes crystallographically disordered rather than inrreversible inorganic network collaps. Importantly, the high‐temperature phase can be kinetically trapped by rapid cooling, establishing cooling rate as a tunable parameter for controlling crystal structure and optical properties. By combining hydrophilic and hydrophobic substrates in an asymmetric hot‐cover configuration, uniform large‐area films are fabricated through interface‐controlled melt spreading and delamination. The melt‐processed films exhibit processing‐dependent self‐trapped exciton emission and circular dichroism associated with the inorganic 1D chains. This work establishes molecular design as a strategy to simultaneously control phase behavior, chirality, excitonic properties, and melt processability in low‐dimensional hybrid semiconductors.