Management of singlet and triplet excitons for efficient white organic light-emitting devices

Lighting accounts for approximately 22 per cent of the electricity consumed in buildings in the United States, with 40 per cent of that amount consumed by inefficient (similar to 15 lm W-1) incandescent lamps(1,2). This has generated increased interest in the use of white electroluminescent organic light-emitting devices, owing to their potential for significantly improved efficiency over incandescent sources combined with low-cost, high-throughput manufacturability. The most impressive characteristics of such devices reported to date have been achieved in all-phosphor-doped devices, which have the potential for 100 per cent internal quantum efficiency(2): the phosphorescent molecules harness the triplet excitons that constitute three-quarters of the bound electron-hole pairs that form during charge injection, and which (unlike the remaining singlet excitons) would otherwise recombine non-radiatively. Here we introduce a different device concept that exploits a blue fluorescent molecule in exchange for a phosphorescent dopant, in combination with green and red phosphor dopants, to yield high power efficiency and stable colour balance, while maintaining the potential for unity internal quantum efficiency. Two distinct modes of energy transfer within this device serve to channel nearly all of the triplet energy to the phosphorescent dopants, retaining the singlet energy exclusively on the blue fluorescent dopant. Additionally, eliminating the exchange energy loss to the blue fluorophore allows for roughly 20 per cent increased power efficiency compared to a fully phosphorescent device. Our device challenges incandescent sources by exhibiting total external quantum and power efficiencies that peak at 18.7 +/- 0.5 per cent and 37.6 +/- 0.6 lm W-1, respectively, decreasing to 18.4 +/- 0.5 per cent and 23.8 +/- 0.5 lm W-1 at a high luminance of 500 cd m(-2).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62889/1/nature04645.pd

Discovery of two new phases of zirconium tetrakis(8-hydroxyquinolinolate): synthesis, crystal structure and their electron transporting characteristics in organic light emitting diodes (OLEDs)

Two new phases of zirconium tetrakis(8-hydroxyquinolinolate) (Zrq4) have been synthesised and characterised by single crystal X-ray diffraction. Their electrical, electronic, optical and thermal properties have been studied. Their electron transporting characteristics have been investigated in organic light emitting devices where the two phases show remarkable differences in performance. One of the forms (designated a-Zrq4) gives significantly lower operating voltage, higher efficiencies and longer lifetime than the other (designated b-Zrq4) in organic light emitting devices.EPSR

11.1: Invited Paper : Advances in Blue Phosphorescent Organic Light‐Emitting Devices

This paper discusses the latest developments towards a commercial blue phosphorescent organic light emitting device (PHOLED™) technology. Progress towards achieving a high efficiency, long‐lived saturated blue PHOLED is discussed. First, a high efficiency (20% EQE, 45 cd/A), light blue (0.17, 0.39) PHOLED is presented. Next, long‐lived blue PHOLEDs having chromaticity co‐ordinates (0.17, 0.38) and (0.16, 0.29) are estimated to degrade to half their initial luminance of 200cd/m 2 after >100,000 hrs and 17,500 hrs, respectively. Finally, results from PHOLEDs designed to increase blue color saturation and lifetime are presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92011/1/1.2433213.pd

47.4: Blue Phosphorescent Organic Light Emitting Device Stability Analysis

A model based on defect generation by exciton‐polaron annihilation interactions between the emitter and host molecules, in a blue phosphorescent OLED, is shown to fit well with experimental data. A blue PHOLED with (0.15, 0.25) chromaticity is shown to have a half‐life, from 1,000 nits, of 690 hrs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92134/1/1.3069766.pd

Concepciones culturales del VIH/Sida de adolescentes de Bolivia, Chile y México

OBJETIVO: Comprender las dimensiones culturales del VIH/Sida de estudiantes adolescentes. MÉTODOS: Estudio antropológico cognitivo. Realizado en Cochabamba (Bolivia), Talca (Chile) y Guadalajara (México) entre 2007 y 2008. Un total de 184 jóvenes (de 14 y 19 años de edad) fueron seleccionados por muestreo propositivo en centros de estudios de educación media superior de cada país. Fueron utilizadas las técnicas de listados libres y el sorteo de montones. Se indagaron términos asociados al concepto VIH/Sida y grupos de dimensiones conceptuales. Posteriormente se aplicó análisis de consenso mediante factorización de componentes principales y análisis dimensional mediante conglomerados jerárquicos y escalas multidimensionales. RESULTADOS: Las diferencias entre los contextos fueron en el grado de consenso en relación al término de VIH/Sida, ya que fue mayor en Cochabamba. En Talca y Guadalajara los jóvenes mencionaron metáforas de lucha frente a la enfermedad, mientras en Cochabamba se refirieron a la ayuda, apoyo y amor que las personas infectadas deberían recibir. Las coincidencias entre las conceptualizaciones de los jóvenes de los tres países fueron: los riesgos (las prácticas sexuales desprotegidas y el contacto con algunos grupos poblacionales específicos), las consecuencias (muerte física y social, entendida ésta última como el rechazo de la sociedad hacia los enfermos) y la prevención de la enfermedad (con base en la información así como uso del condón). CONCLUSIONES: Para los estudiantes adolescentes el VIH/Sida es una enfermedad causada por prácticas sexuales y consumo de drogas que implica daño, dolor y muerte. Los programas preventivos del VIH/Sida para los adolescentes deben promover la búsqueda de información sobre el tema con bases científicas, y no centrarse en las consecuencias emocionales y sociales de la enfermedad.OBJETIVO: Compreender as dimensões culturais do HIV/Aids por estudantes adolescentes. MÉTODOS: Estudo antropológico cognitivo realizado em Cochabamba (Bolívia), Talca (Chile) e Guadalajara (México), entre 2007 e 2008. O total de 184 jovens (de 14 e 19 anos de idade) foi selecionado por amostragem propositiva em centros de estudos de educação média superior de cada país. Foram utilizadas técnicas de listas livres e classificação da pilha. Foi feita a indagação de termos associados ao conceito HIV/Aids e grupos de dimensões conceituais. Posteriormente, fez-se análise de consenso mediante a fatorização dos componentes principais e análise dimensional mediante conglomerados hierárquicos e escalas multidimensionais. RESULTADOS: As diferenças entre os contextos foram no grau de consenso em relação ao termo HIV/Aids, que foi maior em Cochabamba. Em Talca e Guadalajara os jovens mencionaram metáforas de luta diante da doença, enquanto em Cochabamba eles referiram ajuda, apoio e amor que as pessoas infectadas deveriam receber. As coincidências entre as conceitualizações dos jovens dos três países foram: os riscos (as práticas sexuais desprotegidas e o contato com alguns grupos populacionais específicos), as conseqüências (morte física e social, entendida esta última como o rechaço da sociedade aos doentes) e a prevenção da doença (com base na informação e no uso do preservativo). CONCLUSIONES: Para os estudantes adolescentes, o HIV/Aids é uma doença causada por práticas sexuais e uso de drogas que envolve dano, dor e morte. Os programas preventivos do HIV/Aids para os e as adolescentes devem promover a busca de informação com bases científicas sobre o tema, e não só a que se centra nas conseqüências emocionais e sociais da doença.OBJECTIVE: To understand the cultural dimensions of HIV/AIDS among adolescent students. METHODS: A cognitive anthropological study was undertaken in Cochabamba (Bolivia), Talca (Chile) and Guadalajara (Mexico), during 2007 and 2008. A total of 184 teenagers (from 14 to 19 years old) were selected by purposeful sampling at secondary schools in each country. Free association lists and pile sorts were utilized. Terms associated with the concept of HIV/AIDS and groups of conceptual dimensions were investigated. Subsequently, consensus analysis was performed using factorial principal components and dimensional analysis through hierarchical clusters and multidimensional scales. RESULTS: The differences between the country contexts were in the degree of consensus in relation to the term HIV/AIDS, which was greater in Cochabamba. In Talca and Guadalajara the youths mentioned metaphors of fighting against HIV/AIDS, while in Cochabamba participants talked about help, support and love that infected people should receive. The similarities among conceptions by youth from the three countries were: the risk factors (unprotected sexual practice and contact with specific population groups), the consequences (physical and social death, being the latter understood as social rejection of people living with HIV/AIDS) and the prevention of illness (based on information and condom use). CONCLUSIONS: For adolescent students, HIV/AIDS is a disease caused by sexual practices and drug use and involves harm, pain and death. HIV/AIDS prevention programs for adolescents should promote science based information on the topic and not concentrate only on the emotional and social consequences of HIV/AIDS

Understanding and measuring child welfare outcomes

The new Children\u27s and Family Services Reviews (CFSR) process focuses on the effectiveness of services to children and families by measuring client outcomes. This article reviews the research literature related to child welfare outcomes in order to provide a context for federal accountability efforts. It also summarizes the 2001 federal mandate to hold states accountable for child welfare outcomes and describes California\u27s response to this mandate. Implications of the outcomes literature review and measurement problems in the CFSR process suggest CSFR measures do not always capture meaningful outcomes. Recommendations for change are made

Spectatorship and Social Cognition: Per Persson's Understanding Cinema

This paper places Per Persson's book Understanding Cinema in relation to cognitive film theory and the increasing necessity of it to further engage with the psychological and anthropological literature on social cognition. This paper focuses upon Persson's ability to integrate cognitive and cultural perspectives when explaining a spectator's comprehension of point‐of‐view editing, variable framing and character psychology. It is argued that Persson's theoretical framework would have been more explanatorily complete if it had adopted an analytical dualist stance as a means to theorise the ontologically mixed nature of the psychological processes in question