1D semiconducting nanomaterials are promising candidates for wearable electronic devices, in which variability of form (i.e., flexibility and stretchability) is a crucial factor for achieving stable operation during a user's physical activity. Although many stretchable 1D electronic materials have been suggested, they mainly rely on structural engineering, rather than the intrinsic stretchability of the materials, and hence suffer from electrical instability under mechanical deformation. In this work, stretchable core-shell polymeric nanofibers (NFs) are fabricated using coaxial electrospinning. The stretchable core-shell NFs, which consist of a stretchable core and a semiconducting shell, provide both mechanical robustness and superior electrical properties under external strain. The stretchable core-shell NF-based transistors show high operational stability at up to 30% mechanical strain. Furthermore, fully stretchable organic field-effect transistors fabricated using core-shell NFs and stretchable conductors exhibit stable operation and high optical transparency (71% of transmittance at a wavelength of 550 nm). The core-shell NFs also exhibit excellent optoelectronic properties, including a maximum light responsivity (R) of 84.2 A W-1 and an external quantum efficiency (EQE) of 178.6%, under illumination at a wavelength of 585 nm. The results demonstrate a viable approach to fabricating wearable electronic devices using stretchable core-shell polymeric NFs.

Highly flexible organic nanofiber phototransistors are fabricated on a highly flexible poly(ethylene terephthalate) (PET) textile/poly(dimethylsiloxane) (PDMS) composite substrate. Organic nanofibers are obtained by electrospinning, using a mixture of poly(3,3 ″′ ‐didodecylquarterthiophene) (PQT‐12) and poly(ethylene oxide) (PEO) as the semiconducting polymer and processing aid, respectively. PDMS is used as both a buffer layer for flattening the PET textile and a dielectric layer in the bottom‐gate bottom‐contact device configuration. PQT‐12:PEO nanofibers can be well‐aligned on the textile composite substrate by electrospinning onto a rotating drum collector. The nanofiber phototransistors fabricated on the PET/PDMS textile composite substrate show highly stable device performance (on‐current retention up to 82.3 (±6.7)%) under extreme bending conditions, with a bending radius down to 0.75 mm and repeated tests over 1000 cycles, while those prepared on film‐type PET and PDMS‐only substrates exhibit much poorer performances. The photoresponsive behaviors of PQT‐12:PEO nanofiber phototransistors have been investigated under light irradiation with different wavelengths. The maximum photoresponsivity, photocurrent/dark‐current ratio, and external quantum efficiency under blue light illumination were 930 mA W −1 , 2.76, and 246%, respectively. Furthermore, highly flexible 10 × 10 photosensor arrays have been fabricated which are able to detect incident photonic signals with high resolution. The flexible photosensors described herein have high potential for applications as wearable photosensors.

Recognizing the importance of molecular coplanarity and with the aim of developing new, ideal strong acceptor-building units in semiconducting polymers for high-performance organic electronics, herein we present a simplified single-step synthesis of novel vinylene- and acetylene-linked bis-benzothiadiazole (VBBT and ABBT) monomers with enlarged planarity relative to a conventionally used acceptor, benzothiadiazole (BT). Along these lines, four polymers (PDPP-VBBT, PDPP-ABBT, PIID-VBBT, and PIID-ABBT) incorporating either VBBT or ABBT moieties are synthesized by copolymerizing with centro-symmetric ketopyrrole cores, such as diketopyrrolopyrrole (DPP) and isoindigo (IID), and their electronic, physical, and transistor properties are studied. These polymers show relatively balanced ambipolar transport, and PDPP-VBBT yields hole and electron mobilities as high as 0.32 and 0.13 cm(2) V-1 s(-1), respectively. Interestingly, the acetylenic linkages lead to enhanced electron transportation in ketopyrrole-based polymers, showing a decreased threshold voltage and inverting voltage in the transistor and inverter devices, respectively. The IID-based BBT polymers exhibit the inversion of the dominant polarity depending on the type of unsaturated carbon bridge. Owing to their strong electron-accepting ability and their highly pi-extended and planar structures, VBBT and ABBT monomers should be extended to the rational design of high-performance polymers in the field of organic electronics.

Source/Drain series resistance (Rsd) is extracted using methods applicable to short channel nand p-type FinFETs. Rsd is decomposed into spreading, sheet, and contact resistances using the analytic model considering top and sidewall contact resistivity separately. Resistivity parameters in the analytic model were effectively extracted from experimental data, and the Rsd components with different fin widths were investigated.

2014 International Conference on Solid State Devices and Materials,Impact of High-κ Spacers on Parasitic Effects Considering DC/AC Performance Optimization in Si-Nanowire FETs for sub 10 nm Technology Node

A family of naphthalene diimide (NDI)-based donor (D)-acceptor (A) copolymers with various acene- (benzene (Bz), naphthalene (Np), and pyrene (Py)) and heteroacene-type (selenophene (Se) and thiophene (Th)) donor rings has been designed and synthesized as a means to systematically understand structure property relationships on the subject of the structural factor and electron-donating capability of the donor portions for applications in organic field-effect transistors (OFETs) based on NDIs. Alongside of two categories dealing with the lack or existence of the heteroatoms in the donor framework, the resulting copolymers can also be classified into 'thiophene-free' D-A copolymers (PNDI-Bz, PNDI-Np, PNDI-Py, and PNDI-Se) and thiophene-containing copolymer (PNDI-Th). The results from optical and electronic properties lead to the determination that the empirical electron-donating strength of donor co-units is in the order of Bz < Np < Py < Th < Se. In contrast with the similarity of the LUMO levels (-3.73 similar to-3.82 eV) due to the dominant NDI contribution to the polymer backbone, the HOMO levels are sensitive to the relative electron-donating ability and shown to primarily influence whether unipolar n-channel (PNDI-Bz and PNDI-Np) or ambipolar charge transport (PNDI-Py, PNDI-Se, and PNDI-Th) is observed in OFETs of the NDI-based copolymers. Intriguingly, regardless of the strong electron donors toward efficient intramolecular charge transfer (ICT), the best OFET performance is observed in the acene-based centrosymmetric copolymer PNDI-Np (5.63 x 10(-2) cm(2) V-1 s(-1)) when compared to those of the other copolymers with axisymmetric units. Thus, the present work highlights that the geometric features of the donors in NDI D-A copolymers strongly reflect the carrier mobility dynamics rather than inserting electron-rich donor moieties into the backbone to lower the band gap and further strengthen ICT.

A narrow bandgap polymeric semiconductor, BOC-PTDPP, composed of an alkyl substituted diketopyrrolopyrrole (DPP) and tert-butoxycarbonyl (t-BOC)-protected DPP, is synthesized with a view toward forming hydrogen-bonded networks after the thermal cleavage of t-BOC groups. On page 4128 Joon Hak Oh, Changduk Yang, and co-workers report that the dominant polarity in ambipolar organic transistors based on BOC-PTDPP changes from positive to negative after the thermal cleavage of t-BOC groups.

A narrow bandgap polymeric semiconductor, BOC‐PTDPP , comprising alkyl substituted diketopyrrolopyrrole (DPP) and tert ‐butoxycarbonyl ( t ‐BOC)‐protected DPP, is synthesized and used in organic field‐effect transistors (OFETs). The polymer films are prepared by solution deposition and thermal annealing of precursors featuring thermally labile t ‐BOC groups. The effects of the thermal cleavage on the molecular packing structure in the polymer thin films are investigated using thermogravimetric analysis (TGA), UV‐vis spectroscopy, atomic force microscopy (AFM), Fourier transform infrared (FT‐IR) spectroscopy, and X‐ray diffraction (XRD) analysis. Upon utilization of solution‐shearing process, integrating the ambipolar BOC‐PTDPP into transistors shows p ‐channel dominant characteristics, resulting in hole and electron mobilities as high as 1.32 × 10 −2 cm 2 V −1 s −1 and 2.63 × 10 −3 cm 2 V −1 s −1 , which are about one order of magnitude higher than those of the drop‐cast films. Very intriguingly, the dominant polarity of charge carriers changes from positive to negative after the thermal cleavage of t ‐BOC groups at 200 °C. The solution‐sheared films upon subsequent thermal treatment show superior electron mobility ( μ e = 4.60 × 10 −2 cm 2 V −1 s −1 ), while the hole mobility decreases by one order of magnitude ( μ h = 4.30 × 10 −3 cm 2 V −1 s −1 ). The inverter constructed with the combination of two identical ambipolar OFETs exhibits a gain of ∼10. Reported here for the first time is a viable approach to selectively tune dominant polarity of charge carriers in solution‐processed ambipolar OFETs, which highlights the electronically tunable ambipolarity of thermocleavable polymer by simple thermal treatment.