Coherently coupling distinct spin ensembles through a high-Tc superconducting resonator

The problem of coupling multiple spin ensembles through cavity photons is revisited by using (3,5-dichloro-4- pyridyl)bis(2,4,6-trichlorophenyl) methyl (PyBTM) organic radicals and a high-T-c superconducting coplanar resonator. An exceptionally strong coupling is obtained and up to three spin ensembles are simultaneously coupled. The ensembles are made physically distinguishable by chemically varying the g factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures

An efficient Buchwald-Hartwig amination protocol enables the synthesis of new branched and polymeric hole transport materials for perovskite solar cells

Perovskite solar cells (PSCs) are experiencing tremendous interest due to compatibility with solution processing on a wide range of substrates and very high efficiency. The hole transport layer (HTL) plays a fundamental role in such multistack cells. We propose new branched and polymeric organic HTL derivatives with sustainable synthesis and performances exceeding those of Spiro-OMeTAD, the standard in the field

Face tracking algorithm robust to pose, illumination and face expression changes : a 3D parametric model approach

Considering the face as an object that moves through a scene, the posture related to the camera\u2019s point of view and the texture both may change the aspect of the object considerably. These changes are tightly coupled with the alterations in illumination conditions when the subject moves or even when some modifications happen in illumination conditions (light switched on or off etc.). This paper presents a method for tracking a face on a video sequence by recovering the full-motion and the expression deformations of the head using 3D expressive head model. Taking advantage from a 3D triangle based face model, we are able to deal with any kind of illumination changes and face expression movements. In this parametric model, any changes can be defined as a linear combination of a set of weighted basis that could easily be included in a minimization algorithm using a classical Newton optimization approach. The 3D model of the face is created using some characteristic face points given on the first frame. Using a gradient descent approach, the algorithm is able to extract simultaneously the parameters related to the face expression, the 3D posture and the virtual illumination conditions. The algorithm has been tested on Kanade-Cohn database (Kanade et al., 2000) for expression estimation and its precision has been compared with a standard multi-camera system for the 3D tracking. (G. Ferrigno and A. Pedotti, 1985). Regarding illumination tests, we use synthetic movie created using standard 3D-mesh animation tools and real experimental videos created in very extreme illumination condition. The results in all the cases are promising even with great head movements and changes in the expression and the illumination conditions. The proposed approach has a twofold application as a part of a facial expression analysis system and preprocessing for identification systems (expression, pose and illumination normalization)

Solution-processable thin-film transistors from anthradithiophene (ADT) and naphthothiopene (NT) small molecule-based p-type organic semiconductors

Sustainable green electronics is increasingly needed for a multitude of new applications that will fill daily life in the coming decades. The search for new semiconductor materials that can be used in light, flexible, ultra-thin and scalable devices has been given great attention, and especially directed towards organic materials, such as small molecules or polymers. One of the main strengths in such materials lies in those applications where it is not only important to achieve high performance in terms of electronic mobility but it is essential to have low temperatures, solution-processable, and low-cost manufacturing processes. We present the synthesis of novel, organic, solution-processable, small molecule semiconductor materials based on key synthons (ADT and NT) obtained through sustainable processes. Such p-type, pi-conjugated molecular scaffolds have been obtained through cascade reaction sequences involving, amongst others, direct arylation protocols and cross-aldol condensations, affording organic compounds with intrinsically low E factors. We have realized air-stable, organic thin film transistors with very good performances, and demonstrated their use as UV-VIS photodetecting transistors with responsivity values matching currently available commercial detectors

Hopping photoconductivity in an exponential density of states

Photoconductivity in organic semiconductors is modeled taking into account the hopping nature of charge transport in an exponential density of states and exploiting the transport energy concept. Explicit and analytical expressions describing device behavior are obtained, and a robust procedure is outlined to extract from experimental measurements relevant material parameters, including the charge density dependent bulk mobility, as we show on a prototypical all-organic photoconductor. This qualifies the photoconductor not only as a technologically relevant device but also as a test bed for the optoelectronic characterization of disordered materials

The pH- And salt-controlled self-assembly of [1]benzothieno[3,2-b][1]-benzothiophene-peptide conjugates in supramolecular hydrogels

Here, we report a [1]benzothieno[3,2-b][1]-benzothiophene (BTBT) derivative functionalized with a β-sheet-forming peptide which alternates in its sequence Phe and Glu residues. The BTBT core is a popular structural motif in the design of high-mobility organic semiconductors. The insertion of the self-assembling subunit allows control of the supramolecular organization. This molecule self-assembles in water to give hydrogels over a broad range of pH values. Hydrogelation is triggered by both pH changes and variations in salt concentrations. Transmission electron microscopy shows the formation of long-range self-assembled 1D structures. The key role of hydrogen bonding and π-π interactions in hierarchical self-assembly is investigated using absorption, emission, infrared and circular dichroism spectroscopy. This is the first example of demonstrating the formation of supramolecular hydrogels containing the BTBT structure