The solid‐state molecular orientation of conjugated polymers is of vital importance for their charge transport properties, where the edge‐on orientation with π‐stacking direction parallel to the surface is generally preferable to achieving high‐mobility planar field‐effect transistors. However, so far, little is known about the origin of packing‐orientation formation in thin films. Here, it is shown that the solution‐state supramolecular structure of widely studied PffBT4T‐based polymers can be reversibly tuned between 1D worm‐like and 2D lamellar structures for the same polymer/solvent system through solution temperature. Such dimensionality in solution determines the solid‐state packing orientation of the polymer chains, where edge‐on and face‐on textures are generated from solutions with 1D and 2D structures, respectively. More importantly, the transition temperature of solution‐state supramolecular dimensionality is in excellent agreement with that of solid‐state packing orientation. These experimental observations unambiguously demonstrate the predominant roles of solution‐state supramolecular assembly in solid‐state molecular orientation, which is further verified using different molecular weight batches and other two representative polymers. The findings provide new insights into the growth mechanism of polymer semiconductors during transistor fabrication, and open prospective pathways for boosting device performance of solution‐processable plastic electronics.

Conjugated donor−acceptor polymers are a large category of cutting edge semiconductor materials with obvious advantages such as easy processing, light weight, and mechanical flexibility. By rational design of electronwithdrawing and electron-donating moieties, the intermolecular interactions between conjugated polymers can be precisely tuned, realizing the efficient control of polymer aggregation in solution and subsequent polymer packing orientation in solid states. In this Review article, the recent advances on the effect of molecular design on the polymer packing orientation are summarized. The behavior and possible mechanism of molecular orientation are first introduced. Then, the key structural factor, side chains, is systematically discussed with the main focuses on their shape (linear or branched), length, density, position, and symmetry, all of which critically affect the polymer packing. Furthermore, the appropriate substitution of conjugated segments in polymer backbone allows the modulation of the π−π interaction and conjugation length, contributing to the transition between edge-on and face-on arrangements in solid states. Such transition can also be achieved by other influencing factors such as molecular weight, additive, post-treatment, and solvent. In addition, the impact of polymer packing on charge transport in field-effect transistors is reviewed, providing further understanding of structure−property relations for high-performance organic electronic devices.

Cancer is one of the leading diseases threatening human life and health worldwide. Peptide-based therapies have attracted much attention in recent years. Therefore, the precise prediction of anticancer peptides (ACPs) is crucial for discovering and designing novel cancer treatments. In this study, we proposed a novel machine learning framework (GRDF) that incorporates deep graphical representation and deep forest architecture for identifying ACPs. Specifically, GRDF extracts graphical features based on the physicochemical properties of peptides and integrates their evolutionary information along with binary profiles for constructing models. Moreover, we employ the deep forest algorithm, which adopts a layer-by-layer cascade architecture similar to deep neural networks, enabling excellent performance on small datasets but without complicated tuning of hyperparameters. The experiment shows GRDF exhibits state-of-the-art performance on two elaborate datasets (Set 1 and Set 2), achieving 77.12% accuracy and 77.54% F1-score on Set 1, as well as 94.10% accuracy and 94.15% F1-score on Set 2, exceeding existing ACP prediction methods. Our models exhibit greater robustness than the baseline algorithms commonly used for other sequence analysis tasks. In addition, GRDF is well-interpretable, enabling researchers to better understand the features of peptide sequences. The promising results demonstrate that GRDF is remarkably effective in identifying ACPs. Therefore, the framework presented in this study could assist researchers in facilitating the discovery of anticancer peptides and contribute to developing novel cancer treatments.

As a versatile class of semiconductors, diketopyrrolopyrrole (DPP)-based conjugated polymers are well-suited for application of next-generation plastic electronics because of their excellent and tunable optoelectronic properties via rational design of...

Main observation and conclusion A few monolayers of organic semiconductors adjacent to the dielectric layer are of vital importance in organic field‐effect transistors due to their dominant role in charge transport. In this report, the 2‐nm‐thick polymer monolayers based on poly(3‐hexylthiophene) with different molecular weights (Mn) were fabricated using dip‐coating technique. During the monolayer (solid state) formation from the solution, a disorder‐to‐order transition of polymer conformation is observed through UV‐vis absorption measurement. Meanwhile, high Mn polymer monolayer generates higher crystalline fibrillar microstructure than the low Mn one due to the stronger π–π intermolecular packing between polymers. More importantly, the solution aging procedure is utilized to further improve the morphology of polymer monolayers. It is obvious that after aging for 6 d, both fiber dimension and density as well as conjugation length are significantly increased under the same processing conditions in comparison to the fresh solution, and consequently the field‐effect mobilities are remarkably enhanced by 2—4 times. Note that the maximum mobility of 0.027 cm2·V–1·s–1 is among the highest reported values for poly(3‐hexylthiophene) monolayer transistors. These results demonstrate a simple but powerful strategy for boosting the device performance of polymer monolayer transistors.

Since most charge transport in organic field-effect transistors occurs within the first molecular layer closed to the dielectric layer, the monolayer transistors become an ideal platform for transport investigation. Considerable...

Field-effect transistors based on organic semiconducting materials (OFETs) have unique advantages of intrinsically mechanical flexibility, simple preparation process, low manufacturing cost, and large-area preparation. Through the innovation of new material design and device structures, the performance of device parameters such as mobility, on–off current ratio, and the threshold voltage (VTH) of OFETs continues to improve. However, the VTH shift of OFETs has always been an important problem restricting their practical applications. In this work, we observe that the VTH of polymer OFETs with the widely investigated device structure of a SiO2 bottom-gate dielectric is noticeably shifted by pre-applying a large gate voltage. Such a shift in VTH remains to a large extent, even after modifying the surface of the SiO2 dielectric using a hexamethyldisilazane (HMDS) self-assembled monolayer. This behavior of VTH can be ascribed to the charge trappings at the bulk of the SiO2. In addition, the generality of this observation is further proven by using two other conjugated polymers including p-type PDPP3T and n-type PTzNDI-2FT, and a similar trend is obtained.

Downscaling the semiconductor into ultrathin film is of vital importance to high‐performance field–effect transistors (FETs), but the high‐mobility FETs based on conjugated polymer monolayers have been rarely realized. Especially, the lack of high‐performance n‐type polymer monolayer FETs hinders the development of complementary integrated circuits. Herein, by fine‐tuning the supramolecular assembly of two thiazole flanked naphthalene diimide‐based conjugated polymers, the ≈2.5 nm‐thick monolayers with well‐defined fibrillar morphology are grown in a controllable way, where the one‐dimensional solution‐state structures are inherited. The resultant monolayer FETs show the electron mobility up to 0.25 cm2 V−1 s−1, among the record for n‐type polymer monolayer FETs. More importantly, the first demonstration of polymer monolayer complementary integrated circuits is present, and a record‐high inverter gain of 113 is achieved, which is also identical to the best polymer thin‐film inverters.