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Conjugated polymers are of great interest owing to their potential in stretchable electronics to function under complex deformation conditions. To improve the performance of conjugated polymers, various structural designs have been proposed and these conjugated polymers are specially applied in exotic optoelectronics. In this work, a series of all‐conjugated block copolymers (PII2T‐b‐PNDI2T) comprising poly(isoindigo–bithiophene) (PII2T) and poly(naphthalenediimide–bithiophene) (PNDI2T) are developed with varied compositions and applied to electret‐free phototransistor memory. Accordingly, these memory devices present p‐type transport capability and electrical‐ON/photo‐OFF memory behavior. The efficacy of the all‐conjugated block copolymer design in improving the memory‒photoresponse properties in phototransistor memory is revealed. By optimizing the composition of the block copolymer, the corresponding device achieves a wide memory window of 36 V and a high memory ratio of 7 × 104. Collectively, the results of this study indicate a new concept for designing electret‐free phototransistor memory by using all‐conjugated block copolymer heterojunctions to mitigate the phase separation of conjugated polymer blends. Meanwhile, the intrinsic optoelectronic properties of the constituent conjugated polymers can be well‐maintained by using an all‐conjugated block copolymer design. [ABSTRACT FROM AUTHOR]

Recent research interest in organic field‐effect transistor (FET) memory has shifted to the functionality of photoprogramming in terms of its potential uses in multibit data storage and light‐assisted encryption and its low‐energy consumption and broad response to various optical bands. Phototransistor memory can be modulated through both electrical stress and light illumination, allowing it to function as an orthogonal operation method without mutual interference. Herein, the basic design concepts, requirements, and architectures of phototransistor memory are introduced. Design architectures such as channel‐only, channel‐with‐photogate, photochromatic channel devices and floating gate, photoactive polymer, and organic molecule‐based electrets are systematically categorized. The operational mechanism and impact of effective combinations of channels and electrets are reviewed to provide a fundamental understanding of photoprogramming as well as its potential future developmental applications as nonvolatile memory. Furthermore, recent advances in phototransistors and their diverse applications, including nonvolatile memory, artificial synapses, and photodetectors, are summarized. Finally, the outlook for the future development of phototransistors is briefly discussed. A comprehensive picture of the recent progress in phototransistors is provided. [ABSTRACT FROM AUTHOR]

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]

In this study, the authors report a series of conjugated block copolymers, PF‐b‐Piso comprising poly[2,7‐(9,9‐dihexylfluorene)] (PF), and poly(pendent isoindigo) (Piso) for polymer electret in the photonic field‐effect transistor (FET) memory device. The optical properties, surface morphology, and molecular organization of these BCPs are investigated systematically. Accordingly, Piso with absorption in the Ultraviolet C range (UVC, 200–280 nm) possibly rendered the device with a multiband photoresponse, and a good memory performance is achieved by optimizing the polymer composition. Therefore, the memory device comprising PF‐b‐Piso could perform a high current contrast of 106 to 405 nm light and 105 to 254 nm light over 104 s. In addition, a current contrast of 104 and 102 is achieved in response to 650 and 530 nm light, and this phenomenon can be attributed to the charge transfer between channel and memory layers. The experimental results indicate that the block copolymer design not only conduces to forming a self‐assembled microphase separation to stabilize the trapped charge in the polymer electret, but also triggers multiband photoresponding of the photonic FET memory. [ABSTRACT FROM AUTHOR]