Steady-state and time-resolved photoluminescence measurements were collected on Npe:TCNB co-crystals to further probe the interactions between the Npe and TCNB moieties, as shown in Figures and. The emission spectra show a single peak centered near 550 nm, which is red shifted ∼100 nm from that of Npe itself. This shift is associated with CT interactions between Npe and TCNB. The observed fluorescence decay for Npe:TCNB follows a bi-exponential decay with decay components of 2.43 ns (14.6%) and 9.54 ns (85.4%). These values differ from that of pure Npe (1.57 ns) and reflect appreciable electronic interactions in the excited state between the two co-crystal components.