Polymers with an abundant amorphous domain should facilitate energy dissipation upon stretching, making near amorphous π-conjugated polymers have immense potential in realizing intrinsically stretchable field-effect transistor (FET) devices. In this study, high mobility preservation under the stretched state is attempted by replacing typical alkyl-monothienyl (T-R) on a benzo­[1,2-b:4,5-b’]­dithiophene-difluorobenzothiadiazole backbone with three other biaxially extended side-chains, including alkyl-dithienyl (2T-R), branching alkyl-trithienyl (3T-R), and alkyl-benzotrithienyl (B3T-R) groups. Despite showing near amorphous features, the semi-2D BDT-based polymers with bulkier biaxially extended side chains (PBDT-2T, PBDT-3T, and PBDT-B3T) still present comparable mobility to the reference semicrystalline polymer (PBDT-T). Although these four polymers yield comparable mobility, they show distinctly different mobility retention in the stretched state. From the study of their mobility-stretchability relationship, the interdigitating and/or entanglement of these biaxially extended conjugated side chains are shown to play a nontrivial role in the resultant mechanical robustness against the stretching force. Owing to the proper spatial mobility and geometry, the branched 3T-R side chain possesses a more intense interdigitating and/or entanglement capability than the linear 2T-R one and the fused B3T-R one, providing better mechanical strength under stretched states. Meanwhile, it maintains sufficient interchain connectivity for intermittent interchain hopping to compensate for the 1D charge transport along the backbone, ensuring good charge transport even in the stretched state. As a result, the printed PBDT-3T film is demonstrated to deliver a high mobility retention of 73% at a 60% strain exerted parallel to the charge-transporting direction and a very stable mobility retention of 88% after 1000 stretching-releasing cycles at a 60% strain, being one of the best stretchable near amorphous conjugated polymers reported thus far. Our result underlines the effectiveness of using biaxially extended conjugated side chains to realize high-performance stretchable polymers.

To realize high-performance and intrinsically stretchable materials for field-effect transistor (FET) devices, a plethora of approaches about structure design have been explored. Herein, we report a new approach to control the carrier mobility–stretchability properties of the polymers by tuning the hydrophilicity and asymmetric side-chain combination. A series of isoindigo–bithiophene (II2T)-based semiconducting polymers with three kinds of side chains including carbosilane side chain, semifluorinated side chain, and oligoether side chain were synthesized for investigating the structure–mobility and structure–stretchability relationships. The experimental results showed that the molecular stacking pattern and orientation of the derived polymers could be controlled by altering the hydrophilicity and asymmetric side-chain combination. The side chains of carbosilane and oligoether and a semifluorinated side chain could provide an order edge-on stacking, conformability and backbone aggregation, and an irregular solid-state aggregation, respectively. Among them, P­(Si–O) with oligoether and a carbosilane side chain exhibited an enhanced μh of 0.56 cm2 V–1 s–1, edge-on stacking, and aggregation behavior owing to the favorable intermolecular interaction between the oligoether side chain and the asymmetric side chain to mitigate the steric hindrance. Also, P­(Si–O) possessed a remarkable stretchability of (92%,⊥, 82%,∥) orthogonal μh retention under 100% strain and almost unchanged μh was observed after 1000 stretching–releasing cycles at 60% strain. The experimental results suggested that the combination and hydrophilicity of side chain played a pivotal role in developing semiconducting polymers with a high performance and an intrinsic stretchability.

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...

Organic phototransistor memory has received significant attention owing to its solution processability and flexibility, and its high transmission speed and low energy consumption with light operation provide a promising future in ultrahigh-density data storage devices. In this study, TIPSfunctionalized organic small molecules, 9,10-bis[(triisopropylsilyl)ethynyl]anthracene (TIPS-3), 5,12-bis((triisopropylsilyl)ethynyl)tetracene (TIPS-4), and 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-5) were introduced and employed as the photogates, while polystyrene (PS) acted as the insulator in the floating gate electrets of phototransistor memory. The TIPS-functionalized structure enabled acenes to be solution-processable, and PS helped to trap charges efficiently. The devices were photowritten with different kinds of light and were electrically erased with a gate voltage of −60 V for 1 s. TIPS-4 exhibited the best memory performance and photoresponse with a stable current contrast of 10 5 over 10 4 s and a large shift in threshold voltage of 50 V to 450 nm light. The outstanding charge-trapping capability of TIPS-4 in the phototransistor memory was attributed to the favorable energy level alignment to the semiconducting layer. Notably, the significant photoresponse was ascribed to the singlet fission to triplet photodynamics of TIPS-4, which showed a delayed exciton lifetime providing enough time for charge transfer to the channel layer. The results of this study provide a design concept on organic small molecules in the floating gate electret.

In this study, a series of arene moieties were introduced on the side chains of a diketopyrrolopyrrole (DPP)based semiconducting polymer, including naphthalene (DPP-NA), anthracene (DPP-AN), and pyrene (DPP-PY) as an electrontrapping site for nonvolatile transistor-type memory. Therefore, the developed conjugated polymers integrate the channel and electret layers to concomitantly transport hole carriers and trap electrons. We found that the conjugations of arene moieties and their energylevel alignments to the conjugated polymer significantly influenced the memory performance. Accordingly, DPP-AN provided a good hole mobility (μ h ) of 0.020 cm 2 V −1 s −1 , a stable memory window (ΔV t ) of 70 V, and an ON/OFF-state current contrast (I ON /I OFF ) of 4 × 10 3 , exhibiting decent flash-type memory behaviors. To further enhance the memory−stretchability property of DPP-AN, DPPSi-AN with the octydodecyl side chain replaced by the carbosilane side chain exhibited a comparable μ h of 0.029 cm 2 V −1 s −1 , an enhanced ΔV t of 81 V, and an I ON /I OFF of 5 × 10 3 . Notably, DPPSi-AN could achieve a high μ h preservation of 53% and a stable ΔV t of 64 V at 60% tensile strain, alongside a μ h preservation of 69% and a slightly decreased ΔV t of 38 V after 600 cyclic stretch tests at 60% tensile strain. The improved memory− stretchability property of DPPSi-AN could be attributed to the favorable energy levels of anthracene that are conducive to electron trapping and ameliorating hole back-trapping. In addition, the anthracene-incorporated side chain reduced the crystallinity of the polymer and the carbosilane side chain rendered more free volume over the space. The side-chain-engineered conjugated polymer can be effectively modulated with different electron-trapping moieties, which also provides facile device fabrication procedures and superior memory performance.