In-plane hierarchical assembly of two-dimensional molecular crystals toward on-chip multimode optical waveguides.

Two-dimensional (2D) organic lateral heterostructures (OLHs) integrating two or more components have important potential applications in optoelectronics. However, the controlled synthesis of 2D OLHs with in-plane tunable emission remains a great challenge owing to the difficulty in the sequential integration of multiple components. Here, a cascaded strategy is demonstrated for the hierarchical assembly of OLHs with in-plane multicolor emission, from red-blue and red-green to lateral red-green-blue (RGB), with a lateral size of ~15 micrometers. The tunable regions of 2D OLHs are realized by synergistic effects of the molecular doping method and the photo-induced oxidation route during the epitaxial growth process. The obtained OLHs can actively achieve full-spectrum light transport from 420 to 720 nanometers depending on different excitation positions and thus function as multimode RGB signal converters. These findings provide insights into the epitaxial growth of OLHs for the development of next-generation organic optoelectronics.