From Molecular Design to Optical Anisotropy: Orientation Control in BODIPY Langmuir‐Blodgett Films

Molecular orientation within ultrathin films is a critical factor in controlling their optical and electronic properties for surface‐based photonics and optoelectronics. In this study, we examine two amphiphilic boron‐dipyrromethene (BODIPY) derivatives, distinguished by the number of hydrophobic alkyl chains, and investigate their organization and optical response using Langmuir–Blodgett deposition. The spatial and orientational distribution of molecules at the nanoscale is determined by combining hyperspectral imaging, photoluminescence radiation pattern analysis, and incidence‐angle‐resolved absorption spectroscopy. We evidence, both experimentally and based on a new and original theoretical model, the formation of organized monolayers exhibiting either in‐plane or perpendicular transition dipole alignment, depending on the molecular symmetry. These results underscore the deep impact of molecular engineering on supramolecular order and anisotropic optical properties at interfaces, providing a robust strategy for the design of functional thin films down to the monolayer level for advanced optical devices.