1,720,961 research outputs found
Tuning the optical band gap of DH6T by Alq3 dopant
No full textDihexyl-sexithiophene (DH6T) was doped with tris (8-hydroxyquinolinate) aluminum (Alq3) to prepare blends of DH6T/ Alq3 by dissolving the mixture in the chloroform/hexane co-solvent. Solid films with different thickness deposited on quartz substrates were obtained from the blends via casting process. Optical absorption spectroscopy has been performed to measure the optical band gap of pure and doped DH6T as well as variations in the band gap with dopant concentration (weight %). This variation in optical band gap with dopant concentration was determined quantitatively with fitted and extrapolated techniques and observed qualitatively from the red shift appeared along the optical absorption spectra. The results showed that within a specific dopant content, the optical energy gap, Eg of DH6T decreases from 2.69 eV to 1.8 eV with increasing dopant concentration to 23.1%
Utilizing a simple and reliable method to investigate the optical functions of small molecular organic films – Alq3 and Gaq3 as examples
No full textTuning the optical band gap of DH6T by Alq3 dopant
No full textDihexyl-sexithiophene (DH6T) was doped with tris (8-hydroxyquinolinate) aluminum (Alq3) to prepare blends of DH6T/Alq3 by dissolving the mixture in the chloroform/hexane co-solvent. Solid films with different thickness deposited on quartz substrates were obtained from the blends via casting process. Optical absorption spectroscopy has been performed to measure the optical band gap of pure and doped DH6T as well as variations in the band gap with dopant concentration (weight %). This variation in optical band gap with dopant concentration was determined quantitatively with fitted and extrapolated techniques and observed qualitatively from the red shift appeared along the optical absorption spectra.The results showed that within a specific dopant content, the optical energy gap, Eg of DH6T decreases from 2.69 eV to 1.8 eV with increasing dopant concentration to 23.1%
Effects of thermal annealing on the optical, spectroscopic, and structural properties of tris (8-hydroxyquinolinate) gallium films grown on quartz substrates
No full textPhotovoltaic performance of organic solar cells based on DH6T/PCBM thin film active layers
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Tris (8-Hydroxyquinolinate) metals for solution-processed organic solar cells / Fahmi Fariq Muhammad
Get PDFThe simple fabrication process involving minimal material usage makes solutionprocessed
organic solar cell (Courses) devices very attractive for harvesting solar
energy. However, production of these devices on a commercial scale has been slow due
to their relatively low power conversion efficiency and stability problems. It is expected
that these obstacles will be surmounted in the future with rigorous studies actively being
done in this field of research. Besides, a complete understanding of some basic
electrical responses of these OSC devices has not been achieved yet. Consequently,
seeking for interesting materials suitable for OSCs application and understanding the
materials contribution are of great importance especially when strategies are targeted for
the enhancement of OSCs. Tris (8-hydroxyquinolinate) metals (Mq3) are well known in
the fabrication of stable organic light emitting diodes (OLEDs) and also for their unique
optoelectronic properties. Very recently, tris (8-hydroxyquinolinate) aluminium (Alq3)
prepared by thermal evaporation has been used as a buffer layer and dopant material to
improve the performance of OSCs. However, its employment in solution-processed
organic solar cells is still rare. Little attention has been paid on the behaviour of this
material when applied in organic solar cells. Therefore, benefiting from the properties of
Mq3 and easy fabrication process of solution-processed organic solar cell, the current
thesis is focused on characterizing the OSCs related physical properties of tris (8-
hydroxyquinolinate) gallium (Gaq3) and aluminium (Alq3) (as representatives of the
Mq3 materials) and then applying them in solution-processed organic solar cells. The
solution-processed OSC devices are based on ternary bulk heterojunction structure
(three components blended all together) of dihexylisexithiophen/Mq3/methanofullerene
(DH6T/Mq3/PCBM). The optoelectronics, spectroscopic, electrochemical, structural,
morphological, and thermal properties of Mq3 materials are first investigated before incorporating them into the photovoltaic active layers of the devices. From the analysis
of physical properties of Mq3 materials as well as the assessment on the electrical
characteristics of the devices, this work suggests that Mq3 can be a good candidate to be
applied in solution-processed OSCs. The photovoltaic and electrical characteristics of
the devices demonstrated that the photocurrent, open circuit voltage, and the
performance of the devices have improved by approximately six times compared to the
devices without Mq3 incorporation. The basic contribution of Mq3 materials for this
improvement is believed to originate from the increase in the number of exciton
generation and their dissociation into free charge carriers. This can be due to the
enlarged area of the donor-acceptors boundaries between each of the DH6T/Mq3 and
DH6T/PCBM moieties, thereby broadening the absorption of photons. Next, Mq3
incorporation can result in the stabilization of the mobility of the charge carriers within
the DH6T donor and Mq3/PCBM acceptors producing a balanced transportation for the
holes and electrons. The results indicated promising approaches for Mq3 materials to be
applied in solution-processed OSCs as incorporation of Mq3 into the devices active
layers considerably enhanced the overall performance and reproducibility of these
devices
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
