White‐Light Flexible Crystal With 180° Folding Induced by Halogen‐Bond Network in Organic‐Inorganic Hybrid Perovskite

ABSTRACT Organic‐inorganic hybrid perovskites (OIHPs) with white‐light emission have significant potential in solid‐state lighting and display due to the designable structure and excellent luminescent properties. However, OIHPs are prone to damage during bending due to the brittleness of crystals, which limits their application in the field of flexible electronics. Herein, the first white‐light flexible OIHP crystal (named CBAP) with a two‐dimensional structure is constructed from 4‐chloro‐benzylamine hydrochloride. CBAP exhibits 180° folding under external force with an ultralow elastic strain of only 0.56% (the lowest record of the flexible crystals). After bending, the white‐light intensity remains nearly 96% of its initial level. After 20 cycles of folding, the CBAP crystal structure remains intact, showing excellent mechanical and optical stability. The halogen‐bond networks (HBNs) formed by terminal Cl atoms of organic molecules not only act as a periodic slip surface endowing CBAP with the ability of elastic deformation but also promote the generation of organic triplet excitons through the heavy atom effect, contributing to the broadband white‐light emission of CBAP. This work breaks through the limitations of traditional white‐light crystalline materials, where the mechanical properties and optoelectronic characteristics are difficult to be compatible, providing a new paradigm for the design of multifunctional flexible optoelectronic materials.