Atom Probe Tomography of Molecular Organic Materials: Sub-Dalton Nanometer-Scale Quantification

In this paper, we demonstrate that atom probe tomography (APT) can be applied to small-molecule organic materials. We show that APT can provide an unprecedented combination of mass resolution of <1 Da, spatial resolution of ∼0.3 nm in z and ∼1 nm in x–y, and analytic sensitivity of ∼50 ppm with no evidence of molecular fragmentation. We discuss two systems that demonstrate the power of APT to uncover structure–property relationships in organic systems that have proven extremely difficult to probe using existing techniques: (1) a previously published model organic photovoltaic system in which we show a chemical reaction occurs at the heterointerface; and (2) a model organic light-emitting diode system in which we show molecular segregation occurs in the emissive layer bulk. These examples illustrate the power of APT to enable new insights into organic molecular materials.