Study of β phase and Chains Aggregation Degrees in Poly(9,9-dioctylfluorene) (PFO) Solution

In this work, the effects of solvation and desolvation on the β phase of poly­(9,9-dioctylfluorene) (PFO) are studied. The content of β phase is approximately calculated for comparison. The content of β phase can be enhanced up to 40% by the solvation effect and become a metastable state; the desolvation effect is a dynamic process and can enhance the content of β phase remarkably by 18%age units. It is found that the contents of β phase are always changing with the aggregation degrees of PFO chains. To fully understand it, the concepts of mesoscopic aggregates and macroscopic aggregates are proposed and well proved by the filtration experiment. In the solution (the ethanol content less than 30%), the mesoscopic aggregates are beneficial to enhance the content of β phase; in the solution (the ethanol content more than 40%), which is close to the condensed state of fabricated optoelectronic film, the macroscopic aggregates can make the content of β phase not only much higher but also stable. The content of β phase can be controlled by changing the aggregation characteristics of PFO chains in solution. This work will be significant in fabricating the optoelectronic devices from solutions to films with high carrier mobility and good stability

Polarized Thin Layer Deposited Electrochemically on Aluminum-Doped Zinc Oxide as a Cathode Interlayer for Highly Efficient Organic Electronics

Herein, we demonstrated a polarized thin film (PBzP2C4) electrochemically deposited from phosphonate and a carbazole-difunctionalized conjugated molecule as an aluminum-doped zinc oxide (AZO) modifier for high-performance inverted organic solar cells (OSCs)/polymer light-emitting diodes (PLEDs). The PBzP2C4 film showed a controllable thickness and fully covered the surface of AZO, resulting in a smooth and uniform electrode. PBzP2C4 modification reduced the W_F of AZO and highly improved the electron extraction/injection in inverted OSCs/PLEDs. As a result, a maximum power conversion efficiency of 10.35% was achieved for inverted OSCs with PTB7-Th:PC₇₁BM as the active layer, and a maximum luminous efficiency of 21.4 cd A^–1 was obtained for inverted PLEDs based on P-PPV

Formation and Growth Mechanisms of Solid-Electrolyte Interphase Layers in Rechargeable Batteries

Battery technology is advancing rapidly with new materials and new chemistries; however, materials stability determining battery lifetime and safety issues constitutes the main bottleneck. Electrolyte degradation processes triggered by electron transfer reactions taking place at electrode surfaces of rechargeable batteries result in multicomponent solid-electrolyte interphase (SEI) layers, recognized as the most crucial yet less well-understood phenomena impacting battery technology. Electrons flow via tunneling from the bare surface of negative electrodes during initial battery charge causing electrolyte reduction reactions that lead to SEI nucleation, but the mechanisms for further growth beyond tunneling-allowed distances are not known. Our first-principles computational studies demonstrate that radical species are responsible for the electron transfer that allows SEI layer growth once its thickness has evolved beyond the electron tunneling regime. In addition, the composition, structure, and properties of the SEI layer depend on the electrolyte, especially on the extent to which they are able to polymerize after reduction. Here we present a detailed study of polymerization mechanisms and propose mechanistic differences for electrolytes yielding a fast and a slow SEI growth. This new understanding leads to firm guidelines for rational electrolyte design

Estudio, catalogación y documentación de la obra de Javier Calvo

Esta Tesis Doctoral plantea un estudio analítico de la obra de Javier Calvo Maiques (Valencia, 1941). A partir de dos objetivos básicos, abordamos en primer lugar, la contextualización de la trayectoria del artista y en segundo lugar, la catalogación y el análisis de sus obras. Para lo cual se documentan alrededor de 1500 piezas entre dibujos y pinturas. Todo ello apoyado sobre una extensa base documental de libros, catálogos, revistas y artículos de prensa que ayudan a trazar los diferentes itinerarios por los que transcurre su proceso creativo. Analizamos desde sus inicios en la Escuela de Bellas Artes de San Carlos de Valencia, en donde su pluralidad pictórica atiende a un lenguaje todavía sin definir. Pasando posteriormente por una formación complementaria en París, referente que, junto a los contactos con los pujantes grupos de vanguardia valenciana, sobre todo en lo que atañe a la investigación formal, propiciará el camino de pureza plástica hacia la abstracción geométrica. Tras este importantísimo periodo constructivista, la dualidad entre neofiguración gestual y matérica, y la neofiguración geométrica y lineal marcará su trayectoria artística, que acompañada de una constante indagación cromática le ha valido el calificativo de pintor virtuoso en el color y la geometría. A lo largo de la segunda mitad del siglo XX, exactamente a principios de los años sesenta, y hasta las primeras décadas del siglo XXI, el pintor valenciano Javier Calvo Maiques ha desarrollado una labor artística incesante, que debe ser reconocida y valorada en el contexto del Arte Valenciano. Su pintura, como el propio carácter del artista extravertido y social, ha gozado siempre de una buena salud, siendo expuesta con gran acogida, en muestras de carácter colectivo o individual, en galerías, museos, certámenes o salones nacionales e internacionales. Los primeros contactos del artista con la vanguardia valenciana se remontan a la Asociación Arte Actual, a principios de la década de los sesenta. Participando en exposiciones colectivas en el Centro de Estudios Norteamericanos, en el Círculo de Bellas Artes o en varios certámenes concernientes a los Salones Valencianos. Otro contacto algo esporádico, pero importante, fue su contribución en algunas exposiciones con el grupo Antes del Arte, agrupación que bajo el auspicio del crítico de arte Vicente Aguilera Cerni pretendió reavivar la geometría optando por un camino de pureza plástica e investigación del espacio y el movimiento, frente al carácter social de otros grupos realistas. La actividad expositiva de Javier Calvo y la crítica es uno de los apartados más desarrollados y extensos de esta tesis doctoral. La hemos abordado en tres registros que se dividen en: área regional, marco nacional y ámbito internacional. Se halla cimentada en múltiples citas que documentan sus exhibiciones con una buena crítica de prensa, o bien quedan acompañadas de referencias de los catálogos y revistas. Todo ello ha generado y contribuido a un ejercicio muy detallado con testimonios de especialistas en el campo de la historia del arte y la estética. Este primer bloque, el área regional, es el más numeroso, pues reúne la cuantiosa actividad de 116 exhibiciones, desde un periodo muy amplio que registra el año 1959 como fecha de inicio hasta el actual 2017. En el marco nacional, este apartado engloba principalmente las dos primeras décadas expositivas, es decir, los años sesenta y setenta con 25 exposiciones. La tercera división se acerca al registro internacional con 16 muestras. Aunque menor en cantidad no podemos calificarlo carente de interés o importancia. La actividad expositiva se expande mayoritariamente en el área geográfica europea. Los lenguajes artísticos es otro de los grandes apartados desarrollados en esta tesis doctoral y van estrechamente ligados al bloque de catalogación y análisis de la obra. Los lenguajes plásticos se plantean agrupados en tres bloques que pasamos a nombrar a continuación: A. Primeras obras y lenguajes plásticos, B. Neofiguración gestual y C. Geometría. Presentando el primero de ellos, se observa un abanico de variaciones poéticas, que se dilatan mayoritariamente en su etapa de formación. Son obras sueltas, puesto que no se integran en ninguna serie concreta, aunque las hemos agrupado según sus propias características plásticas, en lenguajes artísticos como: Expresionismo, Fauvismo, Pop y Expresionismo abstracto. En general esta etapa determina una pluralidad de estilos afines a la investigación y bajo parámetros todavía jóvenes en la técnica y en la semántica. El segundo grupo B., Neofiguración gestual, es el más extenso y se subordina a una plástica más gestual, libre, dinámica y colorista sin poderla encerrar categóricamente en un lenguaje estricto o único, pero se vincula mayoritariamente a lo figurativo, aunque en ciertos cuadros roza lo abstracto. Encontramos series bien concebidas en sus límites creativos, siempre bajo epígrafes que nos orientan sobre la inspiración del artista para desarrollarlas, normalmente atendiendo a los viajes realizados. El autor las integra en aspectos unificadores y distintivos de sus restantes colecciones hermanas. Son series llenas de vigor artístico, donde el color y la expresión gestual perfilan la esencia de este bloque. El tercer grupo C., Geometría, manifiesta una huella de identidad genuina del artista tanto o más que el resto de su producción total. Bajo la genérica voz de Geometría se abren dos vertientes muy claras, por un lado, la más pura por su lenguaje formal, calculador, constructivista y de colores planos que integraría el capítulo Abstracción geométrica. Por otro lado, una expresión más identificable de referencia exterior a la naturaleza, a la figura humana o a la arquitectura, pero subordinada a un lenguaje geométrico basado en elementos rectilíneos, tanto en la forma como en el fondo en la mayoría de ocasiones, la hemos llamado Neofiguración geométrica. En definitiva construcciones de polígonos y poliedros que conforman una composición visual sugestiva. Como conclusión general, podemos decir que Javier Calvo se ha labrado un justo y merecido reconocimiento en los círculos artísticos valencianos, por una trayectoria artística y expositiva de dilatada y lógica evolución. Así lo atestiguan la multitud de citas y referencias historiográficas que esta tesis ha aportado sobre la crítica recibida y los estudios artísticos sobre su quehacer pictórico, a lo largo de sesenta años. El valor cultural de su legado radica en la regeneración de su facultad creativa y en la incesante investigación de las posibilidades plásticas llevadas a cabo en cada serie hasta la actualidad. Por todo ello, su figura es una apuesta que rebasa los límites regionales. Su obra enriquece no solo el Patrimonio Artístico Valenciano sino el del Arte Español Contemporáneo, por lo tanto esta tesis es un trabajo que intenta situar a nuestro artista justamente dentro de la Historia del Arte Español en la encrucijada de los siglos XX y XXI.This Doctoral Thesis presents an analytical study of the work of Javier Calvo Maiques (Valencia, 1941). Based on two basic objectives, we first address the contextualisation of the trajectory of the artist and, second, the cataloging and analysis of his works. For which are documented about 1500 pieces between drawings and paintings. All this supported by an extensive documentary base of books, catalogs, magazines and press articles that help to trace the different itineraries through which the creative process takes place. We analyze from its beginnings in the School of Fine Arts of San Carlos of Valencia, where its pictorial plurality attends to a still undefined language. Afterwards, he underwent complementary training in Paris, which, together with the contacts with the powerful Valencian avant-garde groups, especially with regard to formal research, will propitiate the path of plastic purity towards geometric abstraction. After this very important constructivist period, the duality between gestural and material neofiguration and the geometric and linear neofiguration will mark his artistic trajectory, which, along with a constant chromatic inquiry, has earned him the qualification of a virtuoso painter in color and geometry. Throughout the second half of the 20th century, exactly in the early sixties, and until the first decades of the 21st century, the Valencian painter Javier Calvo Maiques has developed an incessant artistic work that must be recognized and valued in the context of the Valencian Art. His painting, like the character of the extraverted and social artist, has always enjoyed good health, being exhibited with great acceptance, in samples of collective or individual character, in galleries, museums, contests or national and international salons. The first contacts of the artist with the Valencian avant-garde go back to the Association Arte Actual, in the early sixties. Participating in collective exhibitions at the Center for North American Studies, in the Círculo de Bellas Artes or in various competitions concerning the Valencian Salons. Another somewhat sporadic but important contact was his contribution in some exhibitions with the group Before the Art, a group that under the auspices of art critic Vicente Aguilera Cerni sought to revive geometry by opting for a path of plastic purity and investigation of space and movement, compared to the social character of other realistic groups. The expository activity of Javier Calvo and criticism is one of the most developed and extensive sections of this doctoral thesis. We have addressed it in three registers that are divided into: regional area, national framework and international scope. It is based on multiple quotes documenting its exhibitions with a good press review, or are accompanied by references from catalogs and magazines. All this has generated and contributed to a very detailed exercise with testimonies of specialists in the field of art history and aesthetics. This first block, the regional area, is the most numerous, as it brings together the considerable activity of 116 exhibitions, from a very broad period that registers the year 1959 as the date of beginning until the present 2017. In the national context, this section mainly encompasses the first two decades of exhibition, that is, the sixties and seventies with 25 exhibitions. The third division is close to the international registry with 16 samples. Although less in quantity we can not qualify it without interest or importance. The exhibition activity is mainly in the European geographical area. The artistic languages is another of the great sections developed in this doctoral thesis and are closely linked to the block of cataloging and analysis of the work. The plastic languages are grouped into three blocks that we will now name: A. First works and plastic languages, B. Neo-figurative gesture and C. Geometry. Presenting the first of them, a range of poetic variations are observed, which are mostly dilated in their formation stage. They are loose works, since they are not integrated in any specific series, although we have grouped them according to their own plastic characteristics, in artistic languages such as: Expressionism, Fauvism, Pop and Abstract Expressionism. In general this stage determines a plurality of styles related to research and under parameters still young in technique and in semantics. The second group B., Neo-figurative gesture, is the most extensive and is subordinated to a more gestural, free, dynamic and colorist plastic without being able to categorically enclose it in a strict or unique language, but is mostly linked to the figurative, although in certain pictures rubs the abstract. We find series well conceived in their creative limits, always under epigraphs that guide us on the inspiration of the artist to develop them, usually attending to the trips made. The author integrates them into unifying and distinctive aspects of his remaining sister collections. They are series full of artistic vigor, where the color and the gestural expression outline the essence of this block. The third group C., Geometry, manifests a mark of genuine identity of the artist as much or more than the rest of its total production. Under the generic voice of Geometry open two very clear slopes, on the one hand, the purest for its formal language, calculating, constructivist and flat colors that would integrate the chapter Abstraction geometric. On the other hand, a more identifiable expression of reference outside nature, the human figure or architecture, but subordinated to a geometric language based on rectilinear elements, both in the form and in the background on most occasions, we have called geometric Neo-figuration. In short, constructions of polygons and polyhedra that make up a suggestive visual composition. As a general conclusion, we can say that Javier Calvo has earned a fair and well-deserved recognition in Valencian artistic circles, for an artistic and expositive trajectory of long and logical evolution. This is testified by the multitude of quotations and historiographical references that this thesis has contributed on the received criticism and the artistic studies on its pictorial work, over sixty years. The cultural value of his legacy lies in the regeneration of his creative faculty and in the incessant investigation of the plastic possibilities carried out in each series up to the present. For all this, his figure is a bet that goes beyond the regional limits. His work enriches not only the Valencian Artistic Heritage but the Spanish Contemporary Art, therefore this thesis is a work that tries to situate our artist precisely within the History of Spanish Art at the crossroads of the XX and XXI centuries

Enhancing Fluorescence of Naphthalimide Derivatives by Suppressing the Intersystem Crossing

The control over intersystem crossing (ISC) during an excited state of an organic molecule is critical to realize high-efficiency fluorescent materials. We report newly designed naphthalimide (NMI) based emitters (Ph-NMI and TPA-NMI), in which the photoluminescence (PL) efficiency increased by suppressing the intersystem crossing (ISC). The experimental and theoretical analysis revealed that the enlarged energy gap between the lowest singlet state (S₁) and lowest triplet state (T₁), and the mismatched electronic configuration of these two states can effectively suppress the ISC process in Ph-NMI and TPA-NMI as compared to the original H-NMI. Moreover, the electronic configuration of S₁-state changed to the π–π* transition in Ph-NMI and TPA-NMI (n-π* tansition in H-NMI), resulting in large radiation transition rate constant (<i>K</i>_r). Therefore, Ph-NMI and TPA-NMI exhibit significantly improved PL efficiencies when compared with H-NMI. The optimized OLEDs using TPA-NMI as yellow emitting layers in doped device showed high performance with a maximum external quantum efficiency of 5.96%, which is the best device performance ever achieved based on the naphthalimide derivatives