A co-crystallization strategy toward high-performance n-type organic semiconductors through charge transport switching from p-type planar azaacene derivatives

In this work, we demonstrated that the co-crystallization strategy has offered an efficient and promising alternative route to achieve high-performance n-type semiconductors through charge-transport switching from pristine p-type systems. By using a simple "green synthesis" process through molecular "doping" with F₄TCNQ into a p-type planar azaacene derivative TMIQ (0.27 cm² V^-1 s^-1) host, charge transport characteristic switching occurs with a high electron mobility of 0.12 cm² V^-1 s^-1 under atmospheric conditions obtained for the D-A complex TMF4TQ (cocrystal). The reasons for such switching lie in the ingenious energy level and molecular packing arrangement tailoring. Specifically, the insertion of F₄TCNQ molecules has led to packing transformation from herringbone stacking (TMIQ) to a dense 2D brick arrangement and the low-lying LUMO levels (-4.55 eV) aligned to gold electrodes, thereby facilitating efficient electron injection and transport, and ensuring the air-stable nature, which is further confirmed using theoretical calculations. We believe that our work would provide new insights into high-performance air-stable n-type organic semiconductors exploration.