Measurement of Anisotropic Exciton Transport Lengths in Organic Crystals Using Photoetching.

Measuring anisotropic exciton transport in organic crystals goes beyond just assessing one-dimensional (1D) transport. It offers a deeper understanding of how molecular packing and interactions affect exciton transport in different dimensions. However, achieving nanoscale precision in measuring anisotropic exciton transport lengths and linking them to specific crystalline directions remains a formidable challenge. Here the development of a photoetching method is reported to visualize the exciton transport distances as gaps within two-dimensional (2D) crystals, which in turn allows for the use of a scanning electron microscope (SEM) to precisely measure the sizes. The photoetching method combined with hetero-seeded self-assembly enables the use of conventional fluorescence spectrometry for precise determination of anisotropic exciton transport lengths in 2D structures at the nanoscale. Relying on this novel method, It is unexpectedly found that increasing intermolecular interactions in one crystal direction not only improves exciton transport in that dimension but also enhances exciton transport in the other dimension. These findings provide valuable insights for engineering organic materials that require efficient exciton transport across extended distances.