Electrical Double-Layer Transistors Comprising Block Copolymer Electrolytes for Low-Power-Consumption Photodetectors.

Electrical double-layer transistors (EDLTs) have received extensive research attention owing to their exciting advantages of low working voltage, high biocompatibility, and sensitive interfacial properties in ultrasensitive portable sensing applications. Therefore, it is of great interest to reduce photodetectors' operating voltage and power consumption by utilizing photo-EDLT. In this study, a series of block copolymers (BCPs) of poly(4-vinylpyridine)-block-poly(ethylene oxide) (P4VP-b-PEO) with different compositions were applied to formulate polyelectrolyte with indigo carmine salt in EDLT. Accordingly, PEO conduces ion conduction in the BCP electrolyte and enhances the carrier transport capability in the semiconducting channel; P4VP boosts the photocurrent by providing charge-trapping sites during light illumination. In addition, the severe aggregation of PEO is mitigated by forming a BCP structure with P4VP, enhancing the stability and photoresponse of the photo-EDLT. By optimizing the BCP composition, EDLT comprising P4VP16k-b-PEO5k and indigo carmine provides the highest specific detectivity of 2.1 × 107 Jones, along with ultralow power consumptions of 0.59 nW under 450 nm light illumination and 0.32 pW under dark state. The results indicate that photo-EDLT comprising the BCP electrolyte is a practical approach to reducing phototransistors' operating voltage and power consumption.

Reversible Molecular Conformation Transitions of Smectic Liquid Crystals for Light/Bias-Gated Transistor Memory.

In recent years, organic photonic field-effect transistors have made remarkable progress with the rapid development of conjugated polycrystalline materials. Liquid crystals, with their smooth surface, defined layer thickness, and crystalline structures, are commonly used for these advantages. In this work, a series of smectic liquid crystalline molecules, 2,9-didecyl-dinaphtho-thienothiophene (C10-DNTT), 2,7-didecyl-benzothieno-benzothiopene (C10-BTBT), 3,9-didecyl-dinaphtho-thiophene (C10-DNT), and didecyl-sexithiophene (C10-6T), have been used in photonic transistor memory, functioning as both hole-transport channels and electron traps to investigate systematically the reasons and mechanisms behind the memory behavior of smectic liquid crystals. After thermal annealing, C10-BTBT and C10-6T/C10-DNTT are homeotropically aligned from the smectic A and smectic X phases, respectively. The 3D-ordered structure of these smectic-aligned crystals contributed to efficient photowriting and electrical erasing processes. Among them, the device performance of C10-BTBT was particularly significant, with a memory window of 21 V. The memory ratio could reach 1.5 × 106 and maintain a memory ratio of over 3 orders after 10,000 s, contributing to its smectic A structure. Through the research, we confirmed the memory and light/bias-gated behaviors of these smectic liquid crystalline molecules, attributing them to reversible molecular conformation transitions and the inherent structural inhomogeneity inside the polycrystalline channel layer.

Investigating the Mobility-Compressibility Properties of Conjugated Polymers by the Contact Film Transfer Method with Prestrain.

Up to now, researches on the mobility-stretchability of semiconducting polymers are extensively investigated, but little attention was  paid to their morphology and field-effect transistor characteristics under compressive strains, which is equally crucial in wearable electronic applications. In this work, a contact film transfer method is applied to evaluate the mobility-compressibility properties of conjugated polymers. A series of isoindigo-bithiophene conjugated polymers with symmetric carbosilane side chains (P(SiSi)), siloxane-terminated alkyl side chains (P(SiOSiO)), and combined asymmetric side chains (P(SiOSi)) are investigated. Accordingly, a compressed elastomer slab is used to transfer and compress the polymer films by releasing prestrain, and the morphology and mobility evolutions of these polymers are tracked. It is found that P(SiOSi) outperforms the other symmetric polymers including P(Si─Si) and P(SiO─SiO), having the ability to dissipate strain with its shortened lamellar spacing and orthogonal chain alignment. Notably, the mechanical durability of P(SiOSi) is also enhanced after consecutive compress-release cycles. In addition, the contact film transfer technique is demonstrated to be applicable to investigate the compressibility of different semiconducting polymers. These results demonstrate a comprehensive approach to understand the mobility-compressibility properties of semiconducting polymers under tensile and compressive strains.

Tunable Thermoelectric Performance of the Nanocomposites Formed by Diketopyrrolopyrrole/Isoindigo-Based Donor-Acceptor Random Conjugated Copolymers and Carbon Nanotubes.

This paper presents the development of thermoelectric properties in nanocomposites comprising donor-acceptor random conjugated copolymers and single-walled carbon nanotubes (SWCNTs). The composition of the conjugated polymers, specifically the ratio of diketopyrrolopyrrole (DPP) to isoindigo (IID), is manipulated to design a series of random conjugated copolymers (DPP0, DPP5, DPP10, DPP30, DPP50, DPP90, DPP95, and DPP100). The objective is to improve the dispersion of SWCNTs into smaller bundles, leading to enhanced thermoelectric properties of the polymer/SWCNT nanocomposite. This dispersion strategy promotes an interconnected conducting network, which plays a critical role in optimizing the thermoelectric performance. Accordingly, the effects of morphologies on the thermoelectric properties of the nanocomposites are systematically investigated. The DPP95/SWCNT nanocomposite exhibits the strongest interaction, resulting in the highest power factor (PF) of 711.1 µW m-1 K-2, derived from the high electrical conductivity of 1690 S cm-1 and Seebeck coefficient of 64.8 µV K-1. The prototype flexible thermoelectric generators assembled with a DPP95/SWCNT film achieve a maximum power output of 20.4 µW m-2 at a temperature difference of 29.3 K. These findings highlight the potential of manipulating the composition of random conjugated copolymers and incorporating SWCNTs to efficiently harvest low-grade waste heat in wearable thermoelectric devices.

Unraveling the Effect of Stereoisomerism on Mobility-Stretchability Properties of n-Type Semiconducting Polymers with Biobased Epimers as Conjugation Break Spacers.

The development of intrinsically stretchable n-type semiconducting polymers has garnered much interest in recent years. In this study, three biobased dianhydrohexitol epimers of isosorbide (ISB), isomannide (IMN), and isoidide (IID), derived from cellulose, were incorporated into the backbone of a naphthalenediimide (NDI)-based n-type semiconducting polymer as conjugation break spacers (CBSs). Accordingly, three polymers were synthesized through the Migita-Kosugi-Stille coupling polymerization with NDI, bithiophene, and CBSs, and the mobility-stretchability properties of these polymers were investigated and compared with those of their analogues with conventional alkyl-based CBSs. Experimental results showed that the different configurations of these epimers in CBSs sufficiently modulate the melt entropies, surface aggregation, crystallographic parameters, chain entanglements, and mobility-stretchability properties. Comparable ductility and edge-on preferred stacking were observed in polymers with endo- or exo-configurations in IMN- and IID-based polymers. By contrast, ISB with endo-/exo-configurations exhibits an excellent chain-realigning capability, a reduced crack density, and a proceeding bimodal orientation under tensile strain. Therefore, the ISB-based polymer exhibits high orthogonal electron mobility retention of (53 and 56)% at 100% strain. This study is one of the few examples where biobased moieties are incorporated into semiconducting polymers as stress-relaxation units. Additionally, this is the first study to report on the effect of stereoisomerism of epimers on the morphology and mobility-stretchability properties of semiconducting polymers.

Tailoring Wavelength-Adaptive Visual Neuroplasticity Transitions of Synaptic Transistors Comprising Rod-Coil Block Copolymers for Dual-Mode Photoswitchable Learning/Forgetting Neural Functions.

The vision-inspired artificial neural network based on optical synapses has drawn a tremendous amount of attention for emulating biological senses. Although photoexcitation-induced synaptic functionalities have been widely studied, optical habituation via the photoinhibitory pathway is yet to be demonstrated for sophisticated biomimetic visual adaptive systems. Here, the first optical neuromorphic block copolymer (BCP) phototransistor is demonstrated as an all-optical operation responding to various wavelengths, fulfilling photoassisted dynamic learning/forgetting cycles via optical potentiation without gate bias. The polyfluorene BCPs were precisely designed to enable wavelength-adaptive responses, benefiting from interfacial semiconductor/electret morphology and the crystallinity/electron affinity of the BCPs. Notably, this is the first work to simultaneously exhibit fully light-controlled short- and long-term memory based on organic material systems. The device presents a high current contrast above 100-fold and long-term retention over 104 s. As a proof-of-concept for neural networks, a 6 × 6 array of photosynapses performed outstanding visual pattern learning/forgetting with high accuracy. This study exploits the design strategy of a conjugated BCP electret to unleash the full potential of wavelength-adaptive visual neuroplasticity transitions. It provides an effective architecture for designing high-performance and high-storage capacity required applications in next-generation neuromorphic systems.

Controlled Growth of Highly Oriented Perovskite Crystals in Polymer Solutions via Selective Solvent Vapor Diffusion.

Organic-inorganic hybrid perovskites have garnered significant attention in optoelectronics owing to their outstanding tunable optical characteristics. Controlled growth of perovskite nanocrystals from solutions is key for controlling the emission intensity and photoluminescence lifetime of perovskites. In particular, most studies have focused on controlling the crystallization of perovskite through chemical treatment using chelating ligands or physical treatment via antisolvent diffusion, and there exists a trade-off between the photoluminescence intensity and lifetime of perovskites. Herein, a selective solvent vapor-assisted crystallization with the aid of a functional polymer, which nanoscale perovskite crystals are grown andante from precursor solution, is presented for tuning the crystallization and optical properties of a common halide perovskite, methylammonium lead bromide (MAPbBr3 ). The proposed method here produces perovskite nanocrystals in the range of 200-300 nm. The spin-coated thin film formed from the perovskite solution exhibits strong green photoluminescence with a long lifetime. The effects of the functional group and polymer dosage on the crystallization of MAPbBr3 are systematically investigated, and the crystallization mechanism is explained based on a modified LaMer model. This study provides an advanced solution process for precisely controlling perovskite crystallization to enhance their optical properties for next-generation optoelectronic devices.

Sustained Flexible Photonic Transistor Memories Based on Fully Natural Floating Gate Electrets.

Photonic transistor memory with high-speed communication and energy-saving capabilities has emerged as a new data storage technology. However, most floating-gate electrets are composed of quantum dots derived from petroleum or metals, which are either toxic or harmful to the environment. In this study, an environmentally friendly floating-gate electret made entirely from biomass-derived materials was designed for photonic memories. The results show that the photosensitive hemin and its derivative protoporphyrin IX (PPIX) were successfully embedded in a polylactic acid (PLA) matrix. Correspondingly, their disparate photochemistry and core structure strongly affected the photosensitivity and charge-trapping capacity of the prepared electrets. With an appropriate energy-level alignment, the interlayer exciton formed with the correct alignment of energy levels within the PPIX/PLA electret. In addition, the demetallized core offered a unique relaxation dynamic and additional trapping sites to consolidate the charges. Correspondingly, the as-prepared device exhibited a memory ratio of up to 2.5 × 107 with photo-writing-electrical-erasing characteristics. Conversely, hemin demonstrated self-charge transfer during relaxation, making it challenging for the device to store the charges and exhibit a photorecovery behavior. Furthermore, the effect of trapping site discreteness on memory performance was also investigated. The photoactive components were effectively distributed due to the high dipole-dipole interaction between the PLA matrix and PPIX, resulting in a sustained memory performance for at least 104 s after light removal. The photonic memory was also realized on a bio-derived dielectric flexible substrate. Accordingly, a reliable photorecording behavior was observed, wherein, even after 1000 cycles of bending under a 5 mm bending radius, the data was retained for more than 104 s. To our knowledge, it is the first time that a two-pronged approach has been used to improve the performance of photonic memories while addressing the issue of sustainability with a biodegradable electret made entirely from natural materials.

Molecular template growth of organic heterojunctions to tailor visual neuroplasticity for high performance phototransistors with ultralow energy consumption.

The optical and charge transport properties of organic semiconductors are strongly influenced by their morphology and molecular structures. Here we report the influence of a molecular template strategy on anisotropic control via weak epitaxial growth of a semiconducting channel for a dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT)/para-sexiphenyl (p-6P) heterojunction. The aim is to improve charge transport and trapping, to enable tailoring of visual neuroplasticity. The proposed phototransistor devices, comprising a molecular heterojunction with optimized molecular template thickness, exhibited an excellent memory ratio (ION/IOFF) and retention characteristics in response to light stimulation, owing to the enhanced orientation/packing of DNTT molecules and a favorable match between the LUMO/HOMO levels of p-6P and DNTT. The best performing heterojunction exhibits visual synaptic functionalities, including an extremely high pair-pulse facilitation index of ∼206%, ultralow energy consumption of 0.54 fJ, and zero-gate operation, under ultrashort pulse light stimulation to mimic human-like sensing, computing, and memory functions. An array of heterojunction photosynapses possess a high degree of visual pattern recognition and learning, to mimic the neuroplasticity of human brain activities through a rehearsal learning process. This study provides a guide to the design of molecular heterojunctions for tailoring high-performance photonic memory and synapses for neuromorphic computing and artificial intelligence systems.

N-Type Doping of Naphthalenediimide-Based Random Donor-Acceptor Copolymers to Enhance Transistor Performance and Structural Crystallinity.

An integrated strategy of molecular design and conjugated polymer doping is proposed to improve the electronic characteristics for organic field effect transistor (OFET) applications. Here, a series of soluble naphthalene diimide (NDI)-based random donor-acceptor copolymers with selenophene π-conjugated linkers and four acceptors with different electron-withdrawing strengths (named as rNDI-N/S/NN/SS) are synthesized, characterized, and used for OFETs. N-type doping of NDI-based random copolymers using (12a,18a)-5,6,12,12a,13,18,18a,19-octahydro-5,6-dimethyl-13,18[1',2']-benzenobisbenzimidazo[1,2-b:2',1'-d]benzo[i][2.5]benzodiazocine potassium triflate adduct (DMBI-BDZC) is successfully demonstrated. The undoped rNDI-N, rNDI-NN, and rNDI-SS samples exhibit ambipolar charge transport, while rNDI-S presents only a unipolar n-type characteristic. Doping with DMBI-BDZC significantly modulates the performance of rNDI-N/S OFETs, with a 3- to 6-fold increase in electron mobility (µe) for 1 wt % doped device due to simultaneous trap mitigation, lower contact resistance (RC), and activation energy (EA), and enhanced crystallinity and edge-on orientation for charge transport. However, the doping of intrinsic pro-quinoidal rNDI-NN/SS films exhibits unchanged or even reduced device performance. These findings allow us to manipulate the energy levels by developing conjugated copolymers based on various acceptors and quinoids and to optimize the dopant-polymer semiconductor interactions and their impacts on the film morphology and molecular orientation for enhanced charge transport.

High-Performance Phototransistor Memory with an Ultrahigh Memory Ratio Conferred Using Hydrogen-Bonded Supramolecular Electrets.

As the research of photonic electronics thrives, the enhanced efficacy from an optic unit cell can considerably improve the performance of an optoelectronic device. In this regard, organic phototransistor memory with a fast programming/readout and a distinguished memory ratio produces an advantageous outlook to fulfill the demand for advanced applications. In this study, a hydrogen-bonded supramolecular electret is introduced into the phototransistor memory, which comprises porphyrin dyes, meso-tetra(4-aminophenyl)porphine, meso-tetra(p-hydroxyphenyl)porphine, and meso-tetra(4-carboxyphenyl)porphine (TCPP), and insulated polymers, poly(4-vinylpyridine) and poly(4-vinylphenol) (PVPh). To combine the optical absorption of porphyrin dyes, dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) is selected as a semiconducting channel. The porphyrin dyes serve as the ambipolar trapping moiety, while the insulated polymers form a barrier to stabilize the trapped charges by forming hydrogen-bonded supramolecules. We find that the hole-trapping capability of the device is determined by the electrostatic potential distribution in the supramolecules, whereas the electron-trapping capability and the surface proton doping originated from hydrogen bonding and interfacial interactions. Among them, PVPh:TCPP with an optimal hydrogen bonding pattern in the supramolecular electret produces the highest memory ratio of 1.12 × 108 over 104 s, which is the highest performance among the reported achievements. Our results suggest that the hydrogen-bonded supramolecular electret can enhance the memory performance by fine-tuning their bond strength and cast light on a potential pathway to future photonic electronics.

Performance Enhancement of Lead-Free 2D Tin Halide Perovskite Transistors by Surface Passivation and Its Impact on Non-Volatile Photomemory Characteristics.

Two-dimensional (2D) tin (Sn)-based perovskites have recently received increasing research attention for perovskite transistor application. Although some progress is made, Sn-based perovskites have long suffered from easy oxidation from Sn2+ to Sn4+ , leading to undesirable p-doping and instability. In this study, it is demonstrated that surface passivation by phenethylammonium iodide (PEAI) and 4-fluorophenethylammonium iodide (FPEAI) effectively passivates surface defects in 2D phenethylammonium tin iodide (PEA2 SnI4 ) films, increases the grain size by surface recrystallization, and p-dopes the PEA2 SnI4 film to form a better energy-level alignment with the electrodes and promote charge transport properties. As a result, the passivated devices exhibit better ambient and gate bias stability, improved photo-response, and higher mobility, for example, 2.96 cm2 V-1 s-1 for the FPEAI-passivated films-four times higher than the control film (0.76 cm2 V-1 s-1 ). In addition, these perovskite transistors display non-volatile photomemory characteristics and are used as perovskite-transistor-based memories. Although the reduction of surface defects in perovskite films results in reduced charge retention time due to lower trap density, these passivated devices with better photoresponse and air stability show promise for future photomemory applications.

Enhancing the Performance of Electret-Free Phototransistor Memory by Using All-Conjugated Block Copolymer.

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.

Fully Photoswitchable Phototransistor Memory Comprising Perovskite Quantum Dot-Based Hybrid Nanocomposites as a Photoresponsive Floating Gate.

Tremendous research efforts have been dedicated into the field of photoresponsive nonvolatile memory devices owing to their advantages of fast transmitting speed, low latency, and power-saving property that are suitable for replacing current electrical-driven electronics. However, the reported memory devices still rely on the assistance of gate bias to program them, and a real fully photoswitchable transistor memory is still rare. Herein, we report a phototransistor memory device comprising polymer/perovskite quantum dot (QD) hybrid nanocomposites as a photoresponsive floating gate. The perovskite QDs offer an effective discreteness with an excellent photoresponse that are suitable for photogate application. In addition, a series of ultraviolet (UV)-sensitive insulating polymer hosts were designed to investigate the effect of UV light on the memory behavior. We found that a fully photoswitchable memory device was fulfilled by using the independent and sequential photoexcitation between a UV-sensitive polymer host and a visible light-sensitive QD photogates, which produced decent photoresponse, memory switchability, and highly stable memory retention with a memory ratio of 104 over 104 s. This study not only unraveled the mystery in the fully photoswitchable functionality of nonvolatile memory but also enlightened their potential in the next-generation electronics for light-fidelity application.

Tuning Ambipolarity of the Conjugated Polymer Channel Layers of Floating-Gate Free Transistors: From Volatile Memories to Artificial Synapses.

Three-terminal synaptic transistor has drawn significant research interests for neuromorphic computation due to its advantage of facile device integrability. Lately, bulk-heterojunction-based synaptic transistors with bipolar modulation are proposed to exempt the use of an additional floating gate. However, the actual correlation between the channel's ambipolarity, memory characteristic, and synaptic behavior for a floating-gate free transistor has not been investigated yet. Herein, by studying five diketopyrrolopyrrole-benzotriazole dual-acceptor random conjugated polymers, a clear correlation among the hole/electron ratio, the memory retention characteristic, and the synaptic behavior for the polymer channel layer in a floating-gate free transistor is described. It reveals that the polymers with balanced ambipolarity possess better charge trapping capabilities and larger memory windows; however, the high ambipolarity results in higher volatility of the memory characteristics, namely poor memory retention capability. In contrast, the polymer with a reduced ambipolarity possesses an enhanced memory retention capability despite showing a reduced memory window. It is further manifested that this enhanced charge retention capability enables the device to present artificial synaptic characteristics. The results highlight the importance of the channel's ambipolarity of floating-gate free transistors on the resultant volatile memory characteristics and synaptic behaviors.

Harnessing of Spatially Confined Perovskite Nanocrystals Using Polysaccharide-based Block Copolymer Systems.

Metal halide perovskite nanocrystals (PVSK NCs) are generally unstable upon their transfer from colloidal dispersions to thin film devices. This has been a major obstacle limiting their widespread application. In this study, we proposed a new approach to maintain their exceptional optoelectronic properties during this transfer by dispersing brightly emitting cesium lead halide PVSK NCs in polysaccharide-based maltoheptaose-block-polyisoprene-block-maltoheptaose (MH-b-PI-b-MH) triblock copolymer (BCP) matrices. Instantaneous crystallization of ion precursors with favorable coordination to the sugar (maltoheptaose) domains produced ordered NCs with varied nanostructures of controlled domain size (≈10-20 nm). Confining highly ordered and low dimension PVSK NCs in polysaccharide-based BCPs constituted a powerful tool to control the self-assembly of BCPs and PVSK NCs into predictable structures. Consequently, the hybrid thin films exhibited excellent durability to humidity and stretchability with a relatively high PL intensity and photoluminescence quantum yield (>70%). Furthermore, stretchable phototransistor memory devices were produced and maintained with a good memory ratio of 105 and exhibited a long-term memory retention over 104 s at a high strain of 100%.

Impact of the segment ratio on a donor-acceptor all-conjugated block copolymer in single-component organic solar cells.

The development of single-component organic solar cells (SCOSCs) using only one photoactive component with a chemically bonded D/A structure has attracted increasing research attention in recent years. At represent, most relevant studies focus on comparing the performance difference between a donor-acceptor (D-A) conjugated block copolymer (CBC) and the commensurate blending systems based on the same donor and acceptor segments, and still there are no reports on the impact of the segment ratio for a certain D-A CBC on the resultant photovoltaic performance. In this study, we synthesized a D-A all-conjugated polymers based on an n-type PNDI2T block and a p-type PBDB-T donor block but with three different segment ratios (P1-P3) and demonstrate the significance of the D/A segment ratio on photovoltaic performance. Our results reveal that the n-type PNDI2T block plays a more critical role in the inter/intra-chain charge transfer. P1 with a higher content of PNDI2T delivers superior exciton dissociation and charge transfer behavior than P2 and P3, benefitting from its more balanced hole/electron mobility. In addition, a higher packing regularity associated with a more dominant face-on orientation is also observed for P1. As a result, SCOSC based on P1 exhibits the highest PCE among the synthesized CBCs. It also possesses a minimal energy loss due to the better suppressed non-radiative recombination loss. This work provides the first discussion of the impact of the segment ratio for a D-A all-conjugated block copolymer and signifies the critical role of the n-type segment in designing high-performance single-component CBCs.

Fast Photoresponsive Phototransistor Memory Using Star-Shaped Conjugated Rod-Coil Molecules as a Floating Gate.

With the explosive growth in data generation, photomemory capable of multibit data storage is highly desired to enhance the capacity of storage media. To improve the performance of phototransistor memory, an organic-molecule-based electret with an elaborate nanostructure is of great importance because it can enable multibit data storage in a memory device with high stability. In this study, a series of star-shaped rod-coil molecules consisting of perylenediimide (PDI) and biobased solanesol were synthesized in two-armed (PDI-Sol2), four-armed (PDI-Sol4), and six-armed (PDI-Sol6) architectures. Their molecular architecture-morphology relationships were investigated, and phototransistor memory was fabricated and characterized to evaluate the structure-performance relationship of these rod-coil molecules. Accordingly, the memory devices were enabled by photowriting with panchromatic light (405-650 nm) and electrical erasing using a gate bias. The PDI-Sol4-based memory device showed high memory ratios of 10 000 over 10 000 s and a rapid multilevel photoresponse of 50 ms. This achievement is related to the favorable energy-level alignment, isolated nanostructure, and face-on orientation of PDI-Sol4, which eliminated the charge tunneling barrier. The results of this study provide a new strategy for tailoring nanostructures in organic-molecule-based electrets by using a star-shaped rod-coil architecture for high-performance phototransistor memory.

Low-Energy-Consumption and Electret-Free Photosynaptic Transistor Utilizing Poly(3-hexylthiophene)-Based Conjugated Block Copolymers.

Neuromorphic computation possesses the advantages of self-learning, highly parallel computation, and low energy consumption, and is of great promise to overcome the bottleneck of von Neumann computation. In this work, a series of poly(3-hexylthiophene) (P3HT)-based block copolymers (BCPs) with different coil segments, including polystyrene, poly(2-vinylpyridine) (P2VP), poly(2-vinylnaphthalene), and poly(butyl acrylate), are utilized in photosynaptic transistor to emulate paired-pulse facilitation, spike time/rate-dependent plasticity, short/long-term neuroplasticity, and learning-forgetting-relearning processes. P3HT serves as a carrier transport channel and a photogate, while the insulating coils with electrophilic groups are for charge trapping and preservation. Three main factors are unveiled to govern the properties of these P3HT-based BCPs: i) rigidity of the insulating coil, ii) energy levels between the constituent polymers, and iii) electrophilicity of the insulating coil. Accordingly, P3HT-b-P2VP-based photosynaptic transistor with a sought-after BCP combination demonstrates long-term memory behavior with current contrast up to 105 , short-term memory behavior with high paired-pulse facilitation ratio of 1.38, and an ultralow energy consumption of 0.56 fJ at an operating voltage of -0.0003 V. As far as it is known, this is the first work to utilize conjugated BCPs in an electret-free photosynaptic transistor showing great potential to the artificial intelligence technology.

Poly(styrene)-block-Maltoheptaose Films for Sub-10 nm Pattern Transfer: Implications for Transistor Fabrication.

Sequential infiltration synthesis (SIS) into poly(styrene)-block-maltoheptaose (PS-b-MH) block copolymer using vapors of trimethyl aluminum and water was used to prepare nanostructured surface layers. Prior to the infiltration, the PS-b-MH had been self-assembled into 12 nm pattern periodicity. Scanning electron microscopy indicated that horizontal alumina-like cylinders of 4.9 nm diameter were formed after eight infiltration cycles, while vertical cylinders were 1.3 nm larger. Using homopolymer hydroxyl-terminated poly(styrene) (PS-OH) and MH films, specular neutron reflectometry revealed a preferential reaction of precursors in the MH compared to PS-OH. The infiltration depth into the maltoheptaose homopolymer film was found to be 2.0 nm after the first couple of cycles. It reached 2.5 nm after eight infiltration cycles, and the alumina incorporation within this infiltrated layer corresponded to 23 vol % Al2O3. The alumina-like material, resulting from PS-b-MH infiltration, was used as an etch mask to transfer the sub-10 nm pattern into the underlying silicon substrate, to an aspect ratio of approximately 2:1. These results demonstrate the potential of exploiting SIS into carbohydrate-based polymers for nanofabrication and high pattern density applications, such as transistor devices.