The excellent mechanical flexibility of organic electronic devices is expected to open up a range of new application opportunities in electronics, such as flexible displays, robotic sensors, and biological and medical electronic applications. However, one of the major remaining issues for organic devices is their instability, especially their thermal instability, because low melting temperatures and large thermal expansion coefficients of organic materials cause thermal degradation. Here we demonstrate the fabrication of flexible thin-film transistors with excellent thermal stability and their viability for biomedical sterilization processes. The organic thin-film transistors comprise a high-mobility organic semiconductor, dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene, and thin gate dielectrics comprising a 2-nm-thick self-assembled monolayer and a 4-nm-thick aluminium oxide layer. The transistors exhibit a mobility of 1.2 cm(2) V(-1)s(-1) within a 2 V operation and are stable even after exposure to conditions typically used for medical sterilization.

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Monolayer field-effect transistors based on a high-mobility n-type polymer are demonstrated. The accurate control of the long-range order by Langmuir-Schäfer (LS) deposition yields dense polymer packing exhibiting good injection properties, relevant current on/off ratio and carrier mobility in a staggered configuration. Layer-by-layer LS film transistors of increasing thickness are fabricated and their performance compared to those of spin-coated films.

Recent progress in high power ultrafast shortwave and mid-wave infrared lasers has enabled gas-phase high harmonic generation (HHG) in the water window and beyond, as well as the demonstration of HHG in condensed matter. In this Perspective, we discuss the recent advancements and future trends in generating and characterizing soft X-ray pulses from gasphase HHG and extreme ultraviolet (XUV) pulses from solid-state HHG. Then, we discuss their current and potential usage in time-resolved study of electron and nuclear dynamics in atomic, molecular and condensed matters. T abletop attosecond light sources in the soft X-ray (SXR) spectral region based on highharmonic generation are highly desirable in chemical and material sciences since they can spectroscopically identify specific elements, as well as the oxidation states, charge states and even the spin states of those elements 1. One of the important spectral regions is the "water window" (282-533 eV), which covers the atomic K-shell excitation of carbon and oxygen. Although high harmonics in the water window were first generated with Ti:Sapphire lasers centered at 800 nm more than 20 years ago 2,3 , the X-ray photon flux was too low for timeresolved applications. The mechanism of HHG in gases can be explained by the semiclassical three-step model 4-6. When driving laser-field strength reaches~10 8 V m −1 , the bound electron in the atomic gas can tunnel through the Coulomb potential barrier and become a free electron. In the oscillating laser field, the free-electron wave packet may return to its parent ion with the right time of birth. At recombination, the interference between the wave packets of the returning and bound electrons produces an oscillating dipole that emits attosecond radiation. Returning electrons with various kinetic energy will recombine at different times giving rise to the chirp in the attosecond radiation 7. This process repeats twice for every optical cycle. The temporal beating of attosecond pulses results in the high-harmonic combs in the spectral domain. Empowered by the advances in driving lasers with center wavelengths around 1.8 μm, soft X-ray high harmonics can be generated with a moderate intensity of 10 14 W cm −2 (see Box 1 for details). Significant progress has recently been made in developing attosecond light within the water window 8. By spectrally broadening pulses from an Optical Parametric Amplifier (OPA) using a gas-filled hollow-core fiber 9 or by broadband phase matching in an Optical Parametric Chirped Pulse Amplifier (OPCPA) 10 , two-cycle, mJ-level pulses centered with 1 kHz repetition

The ability to reverse the composition profile of active layers by delaminating and transferring P3HT:PCBM thin films has allowed us to probe directly the sole influence of interfacial segregation on solar cell device characteristics on the same device platform.

Grazing-incidence X-ray diffraction and rocking scans have quantified the structure of poly(3-hexylthiophene) and [6,6]-phenyl-C(61)-butyric acid methyl ester in the active layers of organic solar cells. Our study reveals that the device J(SC) correlates with the local structural development of pure PCBM and, to second order, the extent of out-of-plane P3HT π-stacking.

2197 www.MaterialsViews.com wileyonlinelibrary.comcan be straightforwardly controlled down to a few nanometers by co-evaporation of the host and the dopant molecules. [ 2,4,12,13 ] Carrier injection enhancement of several orders-of-magnitude in organic lightemitting diodes and transistors has been demonstrated. [14][15][16][17][18] Doping-induced enhancement of charge carrier collection at small-molecule organic solar cell contacts has also been demonstrated. [ 12,13,19 ] Achieving the same degree of spatial control of dopant profi le for polymerbased devices is more challenging: polymer fi lms are solution-deposited and, although doped fi lms can be obtained via deposition of a solution containing the host and dopant, spatial distribution of the dopants cannot be easily controlled. Sequential spin-coating of undoped and doped fi lms using orthogonal solvents is one possible approach; however, the polymer-solvent compatibility needed for forming high quality fi lms and interfaces is not assured. We present here a conceptually simple approach based on soft-contact transferlamination (SCTL) of a polymer homojunction, using a soft stamp, for example, polydimethylsiloxane (PDMS), as a transfer medium. SCTL has been extensively used in the past for the deposition of metal electrodes [ 20,21 ] or active layers in organic transistors [ 22,23 ] and photovoltaic cells. [24][25][26][27][28] In the present case, two polymer fi lms, one undoped and one doped, are prepared separately via spin-coating, and then joined via SCTL to realize doped hole-injection or -collection contacts for diodes and solar cells. We have previously demonstrated with two polymers, poly(3-hexylthiophene) (P3HT) ( Figure 1 ) and poly[(9-,9-dioctylfl uorenyl-2,7-diyl)-co-(1,4-benzo-{2,1′-3}-thiadiazole)] (F8BT), that the lamination process of undoped fi lms leads to "transparent" homojunctions, that is, interfaces that are electronically and electrically seamless [ 29 ] as evidenced by the facts that i) no signifi cant energy shift of molecular levels occurs across the SCTL junction, and ii) the current injected from either electrode is independent of whether the middle layer consists of a single polymer fi lm of thickness "t", or of two laminated fi lms with the same total thickness "t' . These results demonstrate that SCTL is a viable method for assembling multilayer polymer devices from separately fabricated layers, thus enabling functionalization, doping, and other materials modifi cation of specifi c parts of a device structure. Though demonstrated to work effectively across metal-metal interfaces, this Poly(3-hexylthiophene) (P3HT) is p-doped by the new soluble dopant molybdenum tris[1-(methoxycarbonyl)-2-(trifl uoromethyl)-ethane-1,2-dithiolene] and investigated via photoemission spectroscopy and transport measurements.Soft-contact transfer lamination of thin layers of the doped P3HT on undoped polymer layers is used to create spatially-confi ned doped regions, which serve as hole-injection contacts on P3HT diodes. This strategy is then used to...