Exciton Transport in Molecular Semiconductor Crystals for Spin‐Optoelectronics Paradigm

Organic semiconductors with ultralong-range exciton diffusion length is highly desirable for optoelectronics but currently remain rare. Here, we show the diffusion length of singlet excitons (LD) in 2,6-diphenyl anthracene (DPA) crystals grown by solvent evaporation is up to ~124 nm. These crystals show a previously unseen parallelogram morphology with layer-by-layer edge-on molecular stacking, isotropic optical waveguiding, radiation rate and non-radiation rate constants of 0.15 ns-1 and 0.26 ns-1 respectively, as well as good field effect transistor hole mobility and theoretically computed strong electronic couplings as high as 109 meV. Photoresponse experiments reveal that the photoconductivity of DPA crystals is surprisingly not related to the radiative pathway, but associated with rapid exciton diffusion to crystal surface for charge separation and carrier bimolecular recombination. Taken together, this study shows that DPA with ultralong-range exciton diffusion length is a promising semiconducting material for new organic optoelectronics paradigm.