In this section we compare D-A co-crystal systems with commonly used donor and acceptor molecules previously employed in co-crystal materials with unique optical properties. These two co-crystal systems have the same donor molecule, Npe, and structurally similar acceptors, TCNB and TCNQ. The first acceptor, TCNB, has been used in the synthesis of co-crystals for applications in developing waveguides and photoswitches. The second acceptor, TCNQ, is one of the most widely studied acceptor species due to its high electron affinity (EA). 6,46-49 TCNQ-based cocrystals are known for strong CT character and some exhibit room temperature ambipolar charge transport. While Npe:TCNB co-crystals have recently been of interest in the development of waveguides for integrated photonics, to the authors' knowledge, Npe:TCNQ co-crystals have not been reported to date.