Donor–acceptor type polymers and supramolecules are promising electrets in photonic field‐effect transistor (FET)‐type memory because of their diversified polymer‐structure design and favorable mechanical tolerance. Using intermolecular association, supramolecule electrets can surpass donor–acceptor type polymers with versatile facile combining processes. Currently, there has been no application of charge‐transfer (CT) supramolecules in electrets of photonic FET memory devices. Herein, a novel series of CT‐based supramolecular electrets comprising poly(1‐pyrenemethyl methacrylate) (PPyMA) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ) is used to elucidate the effect of CT on photonic FET memory. Accordingly, memory devices based on the supramolecular electret with an equimolar content of pyrene and TCNQ exhibit superior bistable memory switchability using electrical/photoprograming with UV (365 nm) and green light (525 nm). This shows a broad memory window of 34 V and favorable memory ratio of over 106 after 104 s. The memory performance can be attributed to the favorable molecular association and dispersion between pyrene and TCNQ in the solid state. The results provide evidence that CT‐based supramolecular electrets warrant applications in optoelectronic applications.
Photonic transistor memory has received increasing attention as next-generation optoelectronic devices for light fidelity (Li-Fi) application due to the attractive advantages of ultra-speed, high security, and low power consumption. However, most transistor-type photonic memories developed to date still rely on electrical bias for operation, imposing certain limits on data transmission efficiency and energy consumption. In this study, the dual manipulation of “photo-writing” and “photo-erasing” of a novel photonic transistor memory is successfully realized by cleverly utilizing the complementary light absorption between the photoactive material, n-type BPE-PTCDI, in the active channel and the hybrid floating gate, CH3NH3PbBr3/poly(2-vinylpyridine). The fabricated device not only can be operated under the full spectrum but also shows stable switching cycles of photo-writing (PW)–reading (R)–photo-erasing (PE)–reading (R) (PW–R–PE–R) with a high memory ratio of ∼104, and the memory characteristics possess a stable long-term retention of >104 s. Notably, photo-erasing only requires 1 s light illumination. Due to the fully optical functionality, the rigid gate electrode is removed and a novel two-terminal flexible photonic memory is fabricated. The device not only exhibits stable electrical performance after 1000 bending cycles but also manifests a multilevel functional behavior, demonstrating a promising potential for the future development of photoactive electronic devices.
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.
electrical/optical coupled programming for diversified and efficient multibit data storage. [5][6][7][8] The electrets in FET memory can be divided into three categories: i) floating gate dielectrics, [9][10][11] ii) polymeric electrets, [12][13][14][15] and iii) ferroelectric materials. [16][17][18] Among them, floating gate dielectrics provide the best performance in the discrete localization of photogating materials, which are shown to be a promising candidate to bistably store charges for extended periods without a power supply.The advantages of ultrafast light signal response and the wide bandwidth optical spectrum make photonic FET memory efficacious in photoassisted information recording, image sensing, and capturing. Many floating gate materials have been proposed, including polymer-perovskite (PVSK) hybrid composites, [19][20][21] conjugated polymer blends, [22][23][24] and conjugated block copolymers. [25] The prime factors in evaluating the performance of a photonic memory device using a floating gate electret include i) the uniform dispersion of photogating material among the polymer medium and ii) compatible energy level alignments between the photogating material, insulating medium and channel material. However, polymer composites or blends suffer from poor processability and dispersion. In addition, polymer−PVSK hybrids are confined by less selective and adaptive energy levels and low ambient stability. Our group proposed a type of floating gate with conjugated rod−coil molecules, showing a fast photoresponse, a high current contrast between "photo−ON" and "electrical−OFF" bistable states over 10 5 , and an extremely low programming driving force of 0.1 V. [26,27] The high performance of the photonic FET memory with conjugated rod-coil molecules as electrets can be attributed to the low energy barrier between the memory layer and the channel layer and the trapped charges being effectively blocked in the electret by the ordered end-on orientation. In addition, the conjugated rod−coil molecules exceled in preventing packing frustration that usually occur in polymeric electrets, which significantly deteriorated the homogeneity and yield of the memory device. [28] Highly crystalline molecules with superior charge carrier mobility can be obtained by a single-crystal formation process [29] Rod-like molecules with liquid crystalline phase transitions show highly ordered stacking and orientation, which is promising as the floating gate electret in highperformance 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 (C n -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...
With the growing demands in flexible electronics, the development of plastic and organic materials has gained increased interest. In this focus review, the design concepts and recent advances of organic liquid crystalline materials in optoelectronic devices were introduced. Thermotropic liquid crystalline materials are categorized into three types: calamitic, discotic, and cholesteric types according to the structures of rod‐like, disk‐like, and chiral rod‐like molecules, respectively. Numerous liquid crystalline materials have been successfully incorporated in organic electronic devices. Notably, smectic liquid crystals hold great promise as semiconducting channel, floating gate electret, and charge transporting interlayer in field‐effect transistors, nonvolatile memory, and photovoltaics, respectively. This review sheds light on the great potential and importance of the organic liquid crystalline material for optoelectronic device applications.
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