Single Crystal Microwires of p‐DTS(FBTTh2)2 and Their Use in the Fabrication of Field‐Effect Transistors and Photodetectors

Single crystal microwires of a well‐studied organic semiconductor used in organic solar cells, namely p‐DTS(FBTTh₂)₂, are prepared via a self‐assembly method in solution. The high level of intermolecular organization in the single crystals facilitates migration of charges, relative to solution‐processed films, and provides insight into the intrinsic charge transport properties of p‐DTS(FBTTh₂)₂. Field‐effect transistors based on the microwires can achieve hole mobilities on the order of ≈1.8 cm² V^?1 s^?1. Furthermore, these microwires show photoresponsive electrical characteristics and can act as photoswitches, with switch ratios over 1000. These experimental results are interpreted using theoretical simulations using an atomistic density functional theory approach. Based on the lattice organization, intermolecular couplings and reorganization energies are calculated, and hole mobilities for comparison with experimental measurements are further estimated. These results demonstrate a unique example of the optoelectronic applications of p‐DTS(FBTTh₂)₂ microwires.     

Deterministic Switching of Ferroelectric Bubble Nanodomains

Here, the deterministic and reversible transformation of nanoscale ferroelectric bubbles into cylindrical domains using a scanning probe microscopy (SPM) approach is demonstrated. The bubble domains—sub‐10 nm spheroid topological structures with rotational polarization—can be erased by applying a mechanical force via the SPM tip. Application of an electrical pulse with a specific combination of amplitude and duration can recreate the bubble domain state. This combination of mechanical and electrical passes is essential for realization of reversible transformation as application of only electrical pulses results in complete erasure of the bubble domain state. Effective Hamiltonian‐based simulations reproduce phase sequences for both the mechanical and electric passes and confirm the intrinsic nature of these transitions. This simple and effective pathway for switching between various topological defect states may be exploited for emergent devices.     

Fully Solution‐Processed Small Molecule Semitransparent Solar Cells: Optimization of Transparent Cathode Architecture and Four Absorbing Layers

Semitransparent solar cells (SSCs) can open photovoltaic applications in many commercial areas, such as power‐generating windows and building integrated photovoltaics. This study successfully demonstrates solution‐processed small molecule SSCs with a conventional configuration for the presently tested material systems, namely BDTT‐S‐TR:PC₇₀BM, N(Ph‐2T‐DCN‐Et)₃:PC₇₀BM, SMPV1:PC₇₀BM, and UU07:PC₆₀BM. The top transparent cathode coated through solution processes employs a highly transparent silver nanowire as electrode together with a combination interface bilayer of zinc oxide nanoparticles (ZnO) and a perylene diimide derivative (PDINO). This ZnO/PDINO bilayer not only serves as an effective cathode buffer layer but also acts as a protective film on top of the active layer. With this integrated contribution, this study achieves a power conversion efficiency (PCE) of 3.62% for fully solution‐processed SSCs based on BDTT‐S‐TR system. Furthermore, the other three systems with various colors exhibited the PCEs close to 3% as expected from simulations, demonstrate the practicality and versatility of this printed semitransparent device architecture for small mole­cule systems. This work amplifies the potential of small molecule solar cells for window integration.     

Impedance Measurements as a Simple Tool to Control the Quality of Conjugated Polymers Designed for Photovoltaic Applications

The problem of batch‐to‐batch variation of electronic properties and purity of conjugated polymers used as electron donor and photon harvesting materials in organic solar cells is addressed. A simple method is developed for rapid analysis of electronic quality of polymer‐based materials. It is shown that appearance of impurities capable of charge trapping changes electrophysical properties of conjugated polymers. In particular, a clear correlation between the effective relaxation time τeff and relative photovoltaic performance (η/η_max) is revealed for samples of poly(3‐hexylthiophene) intentionally polluted with a palladium catalyst. This dependence is also valid for all other investigated samples of conjugated polymers. Therefore, fast impedance measurements at three different frequencies allow one to draw conclusions about the purity of the analyzed polymer sample and even estimate its photovoltaic performance. The developed method might find extensive applications as a simple tool for product quality control in the laboratory and industrial‐scale production of conjugated polymers for electronic applications.     

Broadband Omnidirectional Diversion of Light in Hybrid Plasmonic‐Photonic Heterocrystals

Broadband, omnidirectional, and polarization‐independent diversion has been achieved of more than 90% of the light flow intensity off its incidence direction using hybrid metal–dielectric plasmonic‐photonic heterocrystals. These architectures were prepared by depositing metal film on the interface between two photonic crystals of different parameters. The magnitude of light losses was extracted from angle‐resolved measurements of transmission and reflectance spectra. Comparing these data for different stages of constructing the complex architecture, the diffraction in colloidal crystals, the excitation and radiative decay of short‐living surface plasmon polaritons in a corrugated metal film and the eigenmode mismatch at the interface between two different photonic crystals were identified as corroborating physical mechanisms behind the light diversion.     

Conformational Domain Wall Switch

Domain walls in ferroelectric materials have tantalizing potential in disruptive memory and reconfigurable nanoelectronics technologies. Here, a ferroelectric domain wall switch with three distinct addressable resistance states is demonstrated. The device operation hinges on fully controllable and reversible conformational changes of the domain wall. As validated by atomistic simulations consistent with the experiments, using electric field, the shape—and hence the charge state—of the domain wall and ultimately its conduction are altered. Sequential nanoscale transitions of the walls are visualized directly using stroboscopic‐piezoresponse force microscopy and Kelvin probe microscopy. Anisotropic head‐to‐head domain wall injection, stabilized by the majority carrier type of the ferroelectric, BiFeO₃, is identified as the key factor that enables conformational control.     

Low-complexity BCH codes with optimized interleavers for DQPSK systems with laser phase noise

The presence of high phase noise in addition to additive white Gaussian noise in coherent optical systems affects the performance of forward error correction (FEC) schemes. In this paper, we propose a simple scheme for such systems, using block interleavers and binary Bose–Chaudhuri–Hocquenghem (BCH) codes. The block interleavers are specifically optimized for differential quadrature phase shift keying modulation. We propose a method for selecting BCH codes that, together with the interleavers, achieve a target post-FEC bit error rate (BER). This combination of interleavers and BCH codes has very low implementation complexity. In addition, our approach is straightforward, requiring only short pre-FEC simulations to parameterize a model, based on which we select codes analytically. We aim to correct a pre-FEC BER of around \(10^{-3}\). We evaluate the accuracy of our approach using numerical simulations. For a target post-FEC BER of \(10^{-6}\), codes selected using our method result in BERs around 3\(\times \) target and achieve the target with around 0.2 dB extra signal-to-noise ratio.     

Eurotra: General system design

This article gives a general overview of the technical, scientific and philosophical character of the Eurotra machine translation program, outlines its developmental history and lists some plans for future work.The authors thank Steven Krauwer for valuable comments.