Showing papers by "Wen-Chang Chen published in 2017"
TL;DR: Owing to the well photoresponsibility introduced by the embedded nanoparticles, the device is enabled to access multiple wavelength response and the functionalities of recording power/time-dependent illumination under no vertical electrical field.
Abstract: Solution-processable organic-inorganic hybrid perovskite materials with a wealth of exotic semiconducting properties have appeared as the promising front-runners for next-generation electronic devices. Further, regarding its well photoresponsibility, various perovskite-based photosensing devices are prosperously developed in recent years. However, most exploited devices to date only transiently transduce the optical signals into electrical circuits while under illumination, which necessitates using additional converters to further store the output signals for recording the occurrence of light stimulation. Herein, a nonvolatile perovskite-based floating-gate photomemory with a multilevel memory behavior is demonstrated, for which a floating gate comprising a polymer matrix impregnated with perovskite nanoparticles is employed. Owing to the well photoresponsibility introduced by the embedded nanoparticles, the device is enabled to access multiple wavelength response and the functionalities of recording power/time-dependent illumination under no vertical electrical field. Intriguingly, a nonvolatility of photorecording exceeding three months with a high On/Off current ratio over 104 can be achieved.
123 citations
TL;DR: In this paper, poly(butyl acrylate) (PBA) side chain equipped isoindigo-bithiophene (II2T) conjugated polymers have been designed and synthesized for stretchable electronic applications.
Abstract: Poly(butyl acrylate) (PBA) side chain equipped isoindigo-bithiophene (II2T) conjugated polymers have been designed and synthesized for stretchable electronic applications. The PBA segment possesses low glass transition temperature and high softness, offering a great opportunity to improve the mechanical property of semiconducting polymer thin films that typically contain lots of rigid conjugated rings. Polymers with 0, 5, 10, 20 and 100% of PBA side chains, named PII2T, PII2T-PBA5, PII2T-PBA10, PII2T-PBA20, and PII2T-PBA100, were explored, and their polymer properties, surface morphology, electrical characteristics, and strain-dependent performance were investigated systematically. The series polymers showed a charge carrier mobility of 0.06–0.8 cm2 V–1 s–1 with an on/off current ratio over 105 dependent on different amounts of PBA chains as probed using a top-contact transistor device. Moreover, we can still achieve a mobility higher than 0.2 cm2 V–1 s–1 even if 10% of PBA side chains were added (i.e., P...
81 citations
TL;DR: In this paper, the authors investigated the properties of poly(tetrathienoacene-diketopyrrolopyrrole) polymers and found that the polymer has a hole mobility of 0.1 cm2 V−1 s−1 even at 100% strain or after recovered from strain.
Abstract: The design of polymer semiconductors possessing high charge transport performance, coupled with good ductility, remains a challenge. Understanding the distribution and behavior of both crystalline domains and amorphous regions in conjugated polymer films, upon an applied stress, shall provide general guiding principles to design stretchable organic semiconductors. Structure–property relationships (especially in both side chain and backbone engineering) are investigated for a series of poly(tetrathienoacene-diketopyrrolopyrrole) polymers. It is observed that the fused thiophene diketopyrrolopyrrole-based polymer, when incorporated with branched side chains and an additional thiophene spacer in the backbone, exhibits improved mechanical endurance and, in addition, does not show crack propagation until 40% strain. Furthermore, this polymer exhibits a hole mobility of 0.1 cm2 V−1 s−1 even at 100% strain or after recovered from strain, which reveals prominent continuity and viscoelasticity of the polymer thin film. It is also observed that the molecular packing orientations (either edge-on or face-on) significantly affect the mechanical compliance of the polymer films. The improved stretchability of the polymers is attributed to both the presence of soft amorphous regions and the intrinsic packing arrangement of its crystalline domains.
80 citations
TL;DR: In this paper, the memory-type behaviors of novel carbohydrate-block-polyisoprene (MH-b-PI) block copolymers-based devices, including write-once-read-many-times, Flash, and dynamic-random-access-memory, can be easily controlled by the self-assembly nanostructures (vertical cylinder, horizontal cylinder, and order-packed sphere), in which the MH and PI blocks, respectively, provide the charge-trapping and stretchable function.
Abstract: It is discovered that the memory-type behaviors of novel carbohydrate-block-polyisoprene (MH-b-PI) block copolymers-based devices, including write-once-read-many-times, Flash, and dynamic-random-access-memory, can be easily controlled by the self-assembly nanostructures (vertical cylinder, horizontal cylinder, and order-packed sphere), in which the MH and PI blocks, respectively, provide the charge-trapping and stretchable function. With increasing the flexible PI block length, the stretchability of the designed copolymers can be significantly improved up to 100% without forming cracks. Thus, intrinsically stretchable resistive memory devices (polydimethylsiloxane(PDMS)/carbon nanotubes(CNTs)/MH-b-PI thin film/Al) using the MH-b-PI thin film as an active layer is successfully fabricated and that using the MH-b-PI12.6k under 100% strain exhibits an excellent ON/OFF current ratio of over 106 (reading at −1 V) with stable V set around −2 V. Furthermore, the endurance characteristics can be maintained over 500 cycles upon 40% strain. This work establishes and represents a novel avenue for the design of green carbohydrate-derived and stretchable memory materials.
74 citations
TL;DR: In this article, the synthesis, morphology, and properties of poly(3-hexylthiophene)-block-poly(butyl acrylate) (P3HT-b-PBA) for stretchable electronics applications are reported.
Abstract: We report the synthesis, morphology, and properties of poly(3-hexylthiophene)-block-poly(butyl acrylate) (P3HT-b-PBA) for stretchable electronics applications, which are consisted of semiconducting P3HT and low glass transistion temperature (Tg) PBA blocks. The P3HT-b-PBA thin films self-assembled into fibrillar-like nanostructures and maintained the edge-on oreientation even at a low P3HT composition, based on the results from atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXD). By varying the P3HT/PBA ratio, the tensile modulus decreased as the block length of PBA increased, from 0.93 GPa for P3HT to 0.19 GPa for P3HT-b-PBA12k. The field effect transistor (FET) using P3HT-b-PBA as the active layer exhibited a high p-type mobility over 10–2 cm2 V–1 s–1, indicating its good charge transporting ability. Furthermore, the P3HT-b-PBA6k based FET under 100% strain had a high mobility of 2.5 × 10–2 cm2 V–1 s–1 with an on/off ratio of 7.2 × 106, and it maintained over 10–2 cm2 V–1 s–1 fo...
73 citations
TL;DR: The polar elastomer consisting of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP):poly(4-vinylphenol) ( PVP) is demonstrated, which induces the vertical phase separation and significantly reduce current leakage and reduce the crystallization of PVDF segments, which can contribute current hysteresis in the OFET characteristics.
Abstract: A stretchable and mechanical robust field-effect transistor is essential for soft wearable electronics. To realize stretchable transistors, elastic dielectrics with small current hysteresis, high elasticity, and high dielectric constants are the critical factor for low-voltage-driven devices. Here, we demonstrate the polar elastomer consisting of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP):poly(4-vinylphenol) (PVP). Owing to the high dielectric constant of PVDF-HFP, the device can be operated under less than 5 V and shows a linear-regime hole mobility as high as 0.199 cm2 V–1 s–1 without significant current hysteresis. Specifically, the PVDF-HFP:PVP blends induce the vertical phase separation and significantly reduce current leakage and reduce the crystallization of PVDF segments, which can contribute current hysteresis in the OFET characteristics. All-stretchable OFETs based on these PVDF-HFP:PVP dielectrics were fabricated. The device can still keep the hole mobility of approximately 0.1 cm...
73 citations
TL;DR: In this article, an electrodeposition technique was used to prepare SnO2 films at a reduced temperature below 100 oC, which resulted in high crystallinity and conductivity in addition to high transparency across the visible spectrum.
71 citations
TL;DR: In this article, a perovskite-based redox resistive switching memory using CH3NH3PbBr3 nanoparticles (NPs) dispersed in an insulating solid polymer electrolyte, poly(ethylene oxide) (PEO), was presented.
Abstract: This study describes the first perovskite-based redox resistive switching memory using CH3NH3PbBr3 nanoparticles (NPs) dispersed in an insulating solid polymer electrolyte, poly(ethylene oxide) (PEO), and scrutinizes it in detail. Herein, PEO is chosen not only to perform a matrix function due to its ionic conductivity but also to support a preservative material surrounding the CH3NH3PbBr3 NPs to improve their stability. Further, it is revealed that PEO can serve as the chelating agent to coordinate with PbBr2/CH3NH3PbBr3 NPs in consequence of the direct interaction between Pb2+ cations and electron pairs of ether oxygen on the PEO chain to provide a host medium for the Pb2+ cations on both amorphous and crystalline phases. Consequently, it facilitates the associated redox-based reactions to result in the metallic filament formation in the derived device, leading to the write-once-read-many times resistive switching behavior. The field-effect scanning electron microscopy and X-ray photoelectron spectroscopy analyses are conducted to ascertain the detailed mechanism. It is unveiled that a stable dendritic-like filament is grown in the CH3NH3PbBr3 NPs:PEO hybrid film, which is thus proposed to be the origin of the stable low resistive state and recovery of the conductive path during the reverse bias scan. This study presents a new perspective on the perovskite-based resistive memory devices.
59 citations
TL;DR: The present study demonstrated that the FRET-based full-color-fluorescence porous nanofibrous membranes, which exhibit on-off switching and can be used as naked eye probes, have potential for application in water purification sensing filters.
Abstract: Novel red–green–blue (RGB) switchable probes based on fluorescent porous electrospun (ES) nanofibers exhibiting high sensitivity to pH and mercury ions (Hg2+) were prepared with one type of copolymer (poly(methyl methacrylatete-co-1,8-naphthalimide derivatives-co-rhodamine derivative); poly(MMA-co-BNPTU-co-RhBAM)) by using a single-capillary spinneret. The MMA, BNPTU, and RhBAM moieties were designed to (i) permit formation of porous fibers, (ii) fluoresce for Hg2+ detection, and (iii) fluoresce for pH, respectively. The fluorescence emission of BNPTU (fluorescence resonance energy transfer (FRET) donor) changed from green to blue as it detected Hg2+. The fluorescence emission of RhBAM (FRET acceptor) was highly selective for pH, changing from nonfluorescent (pH 7) to exhibiting strong red fluorescence (pH 2). The full-color emission of the ES nanofibers included green, red, blue, purple, and white depending on the particular pH and Hg2+-concentration combination of the solution. The porous ES nanofibers ...
58 citations
TL;DR: This study demonstrates a facile way to efficiently induce strong memory behavior from common p-type conjugated polymers by adding n-type dopant 2-(2-methoxyphenyl)-1, 3-dimethyl-2,3-dihydro-1H-benzoimidazole and suggests that this approach is a general method to induce memory behavior in conjugation polymers.
Abstract: This study demonstrates a facile way to efficiently induce strong memory behavior from common p-type conjugated polymers by adding n-type dopant 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole. The n-type doped p-channel conjugated polymers not only enhance n-type charge transport characteristics of the polymers, but also facilitate to storage charges and cause reversible bistable (ON and OFF states) switching upon application of gate bias. The n-type doped memory shows a large memory window of up to 47 V with an on/off current ratio larger than 10 000. The charge retention time can maintain over 100 000 s. Similar memory behaviors are also observed in other common semiconducting polymers such as poly(3-hexyl thiophene) and poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene], and a high mobility donor–acceptor polymer, poly(isoindigo-bithiophene). In summary, these observations suggest that this approach is a general method to induce memory behavior in conjugated polymers. To the best of the knowledge, this is the first report for p-type polymer memory achieved using n-type charge-transfer doping.
52 citations
TL;DR: In this article, a low-temperature electrodeposited tin oxide (SnO2) electron-transporting layer (ETL) coupled with a thin PCBM ETL and a functional encapsulating layer was used to realize an efficient, stable textile-based flexible PVSC.
Abstract: Organic–inorganic hybrid perovskite solar cells (PVSC) have appeared as promising high power-per-weight power systems for wearable electronic devices. Herein, we utilized a low-temperature electrodeposited tin oxide (SnO2) electron-transporting layer (ETL) coupled with a thin PCBM ETL and a functional encapsulating layer to realize an efficient, stable textile-based flexible PVSC. We first demonstrated that an easily accessible elastomer can serve as an effective encapsulating material for the fabricated flexible PVSC, as exemplified by the largely improved ambient stability and waterproof properties. Furthermore, we established that the good adhesive properties generated by the elastomer can largely enrich the deployable capability of the completed device stack as evidenced by the effortless integration of a completed device stack onto a textile. As a result, a ∼15% textile-based flexible PVSC with improved ambient stability and washable capability was demonstrated. A proof-of-concept device was successfully integrated with other electronic devices on a unitary textile to serve as an efficient power supply system for wearable electronic devices. The findings revealed in this work can promote the future potential applications of PVSCs in wearable device applications.
TL;DR: An overview of renewable materials used in electronics, including passive components (that is, substrates, photoresists, templates and dispersion agents) and active components ( that is, luminescence layers, proton-transporting layers and charge-trapping layers), as well as their future perspective is provided in this paper.
Abstract: Renewable polymers have attracted extensive research interest as substitutes for fossil fuel-based materials because they are sustainable and biodegradable. With the rapid increase in the applications of electronic devices, the integration of renewable polymers with electronics not only enhances the economic benefit of waste natural resources but also conserves our environment. In this review, an overview of renewable materials used in electronics, including passive components (that is, substrates, photoresists, templates and dispersion agents) and active components (that is, luminescence layers, proton-transporting layers and charge-trapping layers), as well as their future perspective is provided. The relationships between chemical structures, their morphologies and the device characteristics will be discussed. It is hoped that this review will stimulate research and generate interest in applications of renewable materials for the electronics industry. Developing renewable polymeric materials for electronics applications is crucial toward next generation of green electronic industry. Current progress on the renewable materials used as the passive and active components in electronics is reviewed, where the correlation between the relationships of chemical structures, morphology and device characteristics is featured. Furthermore, their future perspectives are provided for foreseeable paths in the development of green electronics.
TL;DR: HTSVA provides not only a simple way to achieve BCP fast self- assembly in practical applications but also a tool to study the self-assembly behavior of BCPs under extreme conditions.
Abstract: Block copolymers (BCP) can self-assemble into nanoscale patterns with a wide variety of applications in the semiconductor industry. The self-assembly of BCPs is commonly accomplished by solvent vapor or thermal annealing, but generally these methods require long time (few hours) to obtain nanostructured thin films. In this contribution, a new and ultrafast method (using microwaves) is proposed—high temperature solvent vapor annealing (HTSVA), combining solvent vapor annealing with thermal annealing, to achieve fast and controllable self-assembly of amphiphilic BCP thin films. A promising carbohydrate-based BCP capable of forming cylindrical patterns with some of the smallest feature sizes is used for demonstrating how to obtain a highly ordered vertical cylindrical pattern with sub-10 nm feature sizes in few seconds by HTSVA. HTSVA provides not only a simple way to achieve BCP fast self-assembly in practical applications but also a tool to study the self-assembly behavior of BCPs under extreme conditions.
TL;DR: A new hybrid electrode featuring a high gauge factor of >30, decent stretchability, decent conductivity, and high transmittance was successfully exploited, revealed to originate from the reversible phase separation endowed by the nanogranular-like morphology formed in Ag.
Abstract: In this study, a new hybrid electrode featuring a high gauge factor of >30, decent stretchability (100% of the original conductivity can be retained after 50 cycles of stretching under a 20% strain without prestrain treatment), high transmittance (>70%) across 400–900 nm, and a good sheet resistance (<50 Ω sq–1) was successfully exploited. These superior properties were revealed to originate from the reversible phase separation endowed by the nanogranular-like morphology formed in Ag. Owing to such discrete nanomorphology, the free volume within this Ag electrode is susceptible to the applied tensile strain and the ensuing change in conductivity enables the realization of an efficient strain sensor. Besides, a representative PTB7-th:PC71BM organic photovoltaic (OPV) using this electrode (with the assistance of a wrinkled scaffold to reinforce the stretchability of the active layer) can exhibit a power-conversion efficiency (PCE) of 6% along with high deformability, for which 75% of its original PCE is ret...
TL;DR: In this paper, a stretchable OPV was constructed with a power conversion efficiency of 5.2% and retained 80% of its original PCE after 50 cycles of stretching at 20% strain.
TL;DR: In this paper, a facile method to enhance the ductility of conjugated polymer thin films by using elastomeric substrates with a self-wrinkled structure is demonstrated.
Abstract: In this study, a facile method to enhance the ductility of conjugated polymer thin films by using elastomeric substrates with a self-wrinkled structure is demonstrated. A brittle polymer of poly(selenophene-alt-3,6-dithophene-2-yl-2,5-bis-(2-octyldodecyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione) (PSeDPP) is transferred onto a poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) substrate, which has a wrinkled structure formed during thermal curing. The ductility of the PSeDPP thin film on the fluoroelastomer substrate is significantly improved compared to that on poly(dimethyl siloxane) (PDMS). When the fluoroelastomer is employed in a fully stretchable transistor as the substrate as well as the dielectric layer, the device exhibits ideal transfer characteristics and excellent mechanical robustness. The transistor device with high electrical performance (≈1.51 (cm2 V−1 s−1) mobility, 104 on–off current ratio) can be stretched up to 30% over 2000 cycles and maintain device performance with 7.32 × 10−1 (cm2 V−1 s−1) and ≈104 on–off current ratio. To demonstrate the compatibility of this method with other semiconducting materials, conjugated polymers such as poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(isoindigo-bithiophene) (PII2T-C8C10) are also used as the active layer, and they show similar results to the PSeDPP. Hence, this method demonstrates a general strategy to significantly enhance the ductility of the conjugated polymer thin films, achieving stretchable organic field effect transistors with both high performance and mechanical compliance.
TL;DR: The first environmentally friendly, low‐cost, and multifunctional device is reported, which can act as a pressure sensor, transistor, as well as memory, and can store the pressure information after removing the external stimuli for subsequent manipulation.
Abstract: Keeping the information arising from tactile stimulation, such as pressure and texture of objects, is an essential feature for artificial intelligence. This important characteristic is intimately related to physiological behavior in daily activities. In order to develop next-generation electronic skin for biomimetic prosthetics, repeating the history of a tactile motion is a must-have function. Here, the first environmentally friendly, low-cost, and multifunctional device is reported, which can act as a pressure sensor, transistor, as well as memory. This tactile transistor memory is very sensitive to external pressure and can store the pressure information after removing the external stimuli for subsequent manipulation. This work is a key step for the future development of intelligent robotic systems with learning capability.
01 May 2017-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this article, an externally-initiated Kumada catalyst-transfer polycondensation (KCTP) method was used to synthesize graft copolymers and ABA-type (P3HTs).
Abstract: In this work, we report the synthesis of all-conjugated donor---acceptor (D---A) graft/block copolymers via an externally-initiated Kumada catalyst-transfer polycondensation (KCTP) method. In the first step, end-functional electron acceptor blocks, poly(naphthalene diimide)s (PNDIs), were prepared via the Stille coupling polycondensation. Then, P3HT blocks were polymerized via KCTP initiated by the Ni(COD)2-activated PNDI complexes. Therefore, a series of D---A graft copolymers and ABA-type (P3HTs were initiated from both ends of PNDI) triblock copolymers were successfully synthesized. The polymers were used to fabricate polymer thin film transistors and the results indicated that all the polymers exhibited moderate charge mobilities ranging from 10ź4 to 10ź3 cm2 Vź1 sź1, and they could be further improved by thermal annealing. Finally, all-polymer solar cells were fabricated by using the block copolymers as the single active components or as surfactants. A power conversion efficiency (PCE) of 0.22 % with open circuit voltage (Voc) = 0.55 V, short circuit current density (Jsc) = 0.64 mA/cm2, and fill factor (FF) = 0.62 was recorded by using the donor---acceptor all-conjugated block copolymer as acceptor, and a PCE of 2.28 % with Voc = 0.61 V, Jsc = 7.00 mA/cm2, and FF = 0.54 was obtained when PNDI was used as a surfactant.
TL;DR: In this article, a light-emitting electrochemical cell memory (LECM) was developed based on a LEC platform, which exhibited excellent ternary state memory behavior with high ON2/ON1/OFF current ratios of 106/105/1 as well as excellent stabilities for each respective state.
Abstract: Carbohydrate-based block copolymers, such as maltoheptaose-block-polyisoprene (MHPI), were successfully employed as polyelectrolytes in a light-emitting electrochemical cell (LEC) to realize organic multi-state electrical memory. The observation of distinctive multi-state memristive behavior could be attributed to the controlled ion motion in MHPI and the electron capture capabilities introduced by its constituent hydroxyl groups. The newly developed sandwich-structured memory device is based on a LEC platform as the light-emitting electrochemical cell memory (LECM). Furthermore, the fabricated LECM exhibited excellent ternary-state memory behavior with high ON2/ON1/OFF current ratios of 106/105/1 as well as excellent stabilities for each respective state. The study not only illustrates the use of carbohydrate-based materials as promising electrolytes for LECM applications, but also provides a new horizon in the development of organic multi-state electrical memory devices.
TL;DR: Yasuda et al. as discussed by the authors presented a special issue of Polymer Journal on the topic of photo and Electro-Functional Polymers and Molecular Assemblies, where the broad and growing interest in utilizing such functional molecular, polymer and liquid-crystalline materials as active elements in various devices, including organic photovoltaic cells, transistors and light-emitting diodes.
Abstract: Since the discovery by Shirakawa, Heeger and MacDiarmid that conjugated polymers can be turned into electrically conducting materials,1,2 in the 1970s, the field of organic π-conjugated materials has grown rapidly. The latest decade has seen a tremendous growth in research exploring organic and polymer semiconductors for various practical applications. Materials science on molecular and polymer materials will undoubtedly continue to be a key ingredient for the development of organic electronics and diverse photonic and electronic applications. Recently, Polymer Journal has published special issues focusing on attractive topics in polymer science.3–9 We present this special issue of Polymer Journal on the topic of ‘Photoand Electro-Functional Polymers and Molecular Assemblies’. The broad and growing interest in utilizing such functional molecular, polymer and liquid-crystalline materials as active elements in various devices, including organic photovoltaic cells, transistors and light-emitting diodes, is well represented in this special issue. We have collected 14 Original Articles, 4 Focus Reviews and 4 Reviews from outstanding researchers in Japan, Taiwan, Korea, USA, France, Australia and India. This collection of papers can provide the readers with an overview of the recent progress in this exciting field. As editors, we would like to thank all the authors and referees for their contributions to this special issue. Finally, we believe that this special issue will provide a valuable reference and perspective for many researchers working in polymer science and related fields. Takuma Yasuda1, Wen-Chang Chen2 and Takashi Kato3 INAMORI Frontier Research Center (IFRC), Kyushu University, Fukuoka, Japan; Department of Chemical Engineering, Institute of Polymer Science and Engineering, National Taiwan University, Taipei, Taiwan and Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo, Japan E-mail: yasuda@ifrc.kyushu-u.ac.jp or chenwc@ntu.edu.tw or kato@chiral.t.u-tokyo.ac.jp
01 Oct 2017
TL;DR: In this paper, a new SDD-Maia detector is proposed, consisting of an array of 384 silicon drift detectors (SDDs), each having a surface area of 1 mm2 and the shape of each individual pixel is square in order to coincide with the footprint of the diode-based Maia detector.
Abstract: A new SDD-Maia detector is being currently developed, consisting of an array of 384 silicon drift detectors (SDDs), each having a surface area of 1 mm2. The shape of each individual pixel is square in order to coincide with the footprint of the diode-based Maia detector. Each SDD pixel is made of a few concentric “rings” that supply a voltage gradient to form the drift field within the silicon. The detector has a double metal scheme that supplies biases to the single SDD rings. All 384 anodes of SDDs are connected to individual electronic channels. This effort was motivated by the need of improving the energy resolution and the throughput of existing diode-based Maia detectors.