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Rod‐like molecules with liquid crystalline phase transitions show highly ordered stacking and orientation, which is promising as the floating gate electret in high‐performance photonic field‐effect transistor (FET) memory. In this work, a series of rod‐like molecules, alkyl‐dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (Cn‐DNTT), are investigated with a smectic liquid crystalline phase transition. The photonic FET memory featuring these rod‐like molecules is correlated with their morphology and crystallographic properties. A volatility transition from short−term to long−term memory behavior is found by utilizing the smectic liquid crystalline phase transitions (SmX, X = H, K, E) to orient the stacking in the floating gate. Accordingly, the annealed 2,9‐didecyldinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (C10‐DNTT) polycrystalline film with the optimized alkyl chain length achieved preferential end‐on orientation associated with the herringbone‐type stacking to store charges during photowriting, along with effective charge tunneling for the trapped charges during electrical erasing. Therefore, the resultant photonic FET memory provided a superior ON/OFF current ratio of up to 105 with retention of 104 after 104 s. The results demonstrate that rod‐like molecules with smectic liquid crystalline phase and highly ordered orientation have great potentials for developing high‐performance photonic FET memory. [ABSTRACT FROM AUTHOR]

With the growing demands of light fidelity technology, photonic transistor memory has gained considerable attention for next‐generation optoelectronic devices. In this work, alkylated rylenediimides of 2,9‐diphenethylanthra[2,1,9‐def:6,5,10‐d"e"f]diisoquinoline‐1,3,8,10(2H,9H)‐tetraone (C8‐PDI) and 2,7‐dioctylbenzo[lmn][3,8]phenanthroline‐1,3,6,8(2H,7H)‐tetraone (C8‐NDI), and pyromellitic diimide of 2,6‐dioctylpyrrolo[3,4‐f]isoindole‐1,3,5,7(2H,6H)‐tetraone (C8‐PMDI) have been used as floating gate electrets in the photonic field‐effect transistor‐type memory. The structure‐optics‐performance relationship of these rod‐like molecules has been systematically studied, and the memory device exhibited a decent response to photowriting and electrical erasing processes, owing to the 3D ordered smectic layer structure and brickwork stacking. Therefore, an evenly distributed photogating moiety, efficient exciton dissociation associated with decent carrier tunneling and charge trapping can be obtained. Among them, the sought‐after C8‐NDI presents favorable energy level alignment, multiband photoresponding, and an optimal block ratio. The fabricated photonic memory with C8‐NDI electret presented a remarkable memory switchability with a memory ratio of 104 and a stable memory ratio of 105 over 10,000 s. To the best of knowledge, this is the first work to utilize rylenediimides based liquid crystals as an efficient charge blocking electret, and these findings open an avenue for designing rod‐like molecules with highly ordered liquid crystalline properties in the ultrafast photomemory devices. [ABSTRACT FROM AUTHOR]