2D chirality in organic thin films: advances in nonreciprocal chiroptical properties

Nonreciprocal chiroptical properties in thin films of chiral organic materials have gained remarkable attention in recent years. Originating from the presence of two-dimensional (2D) chiral structures, these properties manifest as an inversion of the handedness of circularly polarized light preferentially transmitted or emitted from opposite faces of the same sample. Here, we provide a comprehensive overview of the most recent advances in this area, discussing representative systems based on organic small molecules, organic polymers, and hybrid organic–inorganic composites, with particular emphasis on elucidating structure–property relationships. Finally, we survey emerging technological applications enabled by nonreciprocal chiroptical responses. By outlining current challenges and open questions, this review aims to stimulate further discussion and inspire new investigations in this rapidly emerging field.