  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 $\lt 1~\mathrm{Da}$, spatial
resolution of $\sim 0.3~\mathrm{nm}$ in z and $\sim 1~\mathrm{nm}$ in x-y, and
analytic sensitivity of $\sim 50~\mathrm{ppm}$ 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.
