1,720,959 research outputs found
효율적인 광 증감 제로 비 풀러렌 기반 2D 평면형 소분자 반도체를 사용하여 초박형 광증 배 포토 다이오드 제작
No full textPhoto Multiplication, Photodetector, Organic Photodiode,High Detectivity, Optical SensitizerIn this work, we explore the possibility of using nonfullerene and a planar n-type small molecular semiconductor, 2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (IDIC) as an optical sensitizer to improve the EQE and to reduce the thickness of the photoactive layer to 70 nm. A key idea of this work is utilizing the unique photophysical properties of IDIC with an anisotropic electron transport. As is well known, contrary to spherical PCBMs (PC61BM and PC71BM) with an isotropic charge transport property, the 2D planar IDIC with an inherently anisotropic packing structure tends to hinder the formation of the effective electron percolation pathways. This is a very important requirement for the optical sensitizer of PM-OPDs because it leads to more efficient charge trapping. In addition, IDIC possesses a relatively higher absorption coefficient in the visible range compared to PC71BM, which can contribute to a higher photocurrent. Together with a deeper lowest unoccupied molecular orbital (LUMO) level of IDIC compared to PC71BM, all the mentioned photophysical properties of IDIC can be much more beneficial as optical sensitizers of the PM-OPDs. Layer-by-layer deposition of P3HT as a photoactive layer and IDIC as an optical sensitizer enables more effective PM operation, yielding high EQE exceeding 130,000% and specific detectivity over 1012 Jones at 150-nm-thick active layer. Furthermore, due to more facile spatial confinement of the charge carriers, the photoactive layer thickness was further decreased down to 70 nm while maintaining reasonably high EQE of 60,000% as well as specific detectivity over 1012 Jones. Physical origins of such synergetic effects of using IDIC as an optical sensitizer are fully discussed with various photophysical analyses in the forthcoming sections.open1 - Introduction 2
1.1 Introduction to PM based Photodetector 2
1.2 Mechanism – Photo Multiplication Type Photodetector 3
1.3 PM Type Photodetector – Advantages and Disadvantages 4
1.4 Recent Trends in PM type Photodiodes 5
1.5 Current Theses Work 7
2 – Experimental Section 9
2.1 Preparations 9
2.1.1 Material Preparations 9
2.1.2 Device Preparations 10
2.2 Characterizations 11
2.2.1 Material Characterization 11
2.2.2 Device Characterization 14
3 – Results and Discussions 17
4 – Conclusions 31본 연구에서는 100 nm 이하의 얇은 광활성층 두께 조건에서 높은 외부 양자 효율을 구현하기 위해, 평면 분자 구조를 가지는 비 풀러렌 전자 받개인 2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (IDIC)의 광학적 감응제(optical sensitizer)로서의 활용 가능성을 타진하였다. 본 연구는 핵심은 기존의 구형 구조를 가지는 풀러렌 계열 전자 받개(PC61BM, PC71BM)에서 보이는 등방적인 전자 전달과는 반대인 IDIC의 비등방적인 전자 전달을 활용하는 것으로, 이러한 비등방적인 패킹 구조는 전자의 효율적인 여과 경로(percolation pathway)의 형성을 저해하게 된다. 따라서 이러한 현상은 전하의 트랩에 있어 굉장히 용이하다고 할 수 있는데, 때문에 광 증폭(photomultiplication) 메커니즘 기반의 유기 포토디텍터(organic photodetector, OPD) 구조에서 광학적 감응제로 적용하기에 적합하다고 할 수 있다. 또한, IDIC는 기존의 풀러렌 계열 전자 받개들에 비해 가시광선 영역의 파장에 대해 더 높은 흡광 계수를 가지는데, 이는 흡광 효율의 향상을 야기하여, 결과적으로 기존에 비해 더 높은 광전류를 구현할 수 있게 한다. 상기 서술한 광물리적인 특성과 더불어, IDIC는 풀러렌 계열 전자 받개에 비해 더 낮은 최저 빈 분자 궤도(lowest unoccupied molecular orbital, LUMO) 준위를 가지는데, 이러한 특성 또한 PM-OPD 구조에서 광학적 감응제로서 풀러렌 계열 전자 받개에 비해 더욱 낫다고 할 수 있다. 소자 구현을 위해, 광활성층으로 IDIC와 함께 poly(3-hexylthiophene-2,5-diyl) (P3HT)을 사용하였고, 소자 성능의 비교를 위해 IDIC 대신 PC71BM을 적용한 소자 또한 제작하였다. 더 효율적인 광 증폭 메커니즘 구현을 위해, P3HT와 IDIC 또는 PC71BM을 층층이 배치(layer-by-layer deposition)하였고, 이를 통해 약 150 nm의 매우 얇은 광활성층을 이용하여 130,000% 이상의 외부 양자 효율과 1012 Jones 이상의 검출능을 가지는 고성능 유기 포토디텍터를 구현할 수 있었다. 또한, 기존 풀러렌 계열 전자 받개를 사용한 경우에 비해 IDIC를 사용할 때 더 강한 전하의 공간적 구속(spatial confinement)이 이루어짐을 확인하여 광활성층의 두께를 더욱 낮추었고, 약 70 nm 정도의 매우 얇은 광활성층 조건에서도 60,000% 이상의 매우 높은 외부 양자 효율을 보임을 확인하였다.MasterdCollectio
PEDOT:PSS modified Screen Printed Graphene-Carbon Ink based Flexible Humidity Sensor
Full text linkIn this work, we present a screen-printed humidity sensor fabricated on a flexible polyvinyl chloride (PVC) substrate. A comparative analysis has been carried out for printed graphene-carbon electrode with and without Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) modification in the humidity sensing range of 25 - 90 %RH. The sensor modified with PEDOT:PSS demonstrated enhanced performance ( ~ 1 %/%RH versus ~ 0.8 %/%RH of unmodified sensor). Further, the enhancement in the performance of the modified sensor was found to be prominent in the low to moderate humidity range (≤60 %RH). The repeatability, response and recovery time were also analysed for both types of sensors and their applicability has been demonstrated for neonatal care by monitoring the humidity level of a wet baby diapers. This demonstration shows the potential application of presented humidity sensors in areas such as environmental monitoring, healthcare, industrial, and agriculture
Influence of Thickness of Screen Printed Carbon Electrodes on Electrochemical Sensing
Full text linkScreen printing is one of the widely used methods for printed sensors and electronics. The performance of these devices could vary with the printing parameters such as thickness of the printed layer, the squeeze length and pressure applied for printing etc. Whilst sensor design and the ink used for the printing of sensitive layers have been studied previously, the vital printing parameters has not attracted much attention. This paper reports the influence of thickness of printed sensor on their electrochemical sensing property. Carbon ink is used to print sensors with three-electrode geometry and their working electrode is modified with MoS2 to study the detection of ascorbic acid. The thicknesses of the sensitive layers varied from ~4 µm to 120 µm as the number of printed layers of ink increased from 1 to 5, 10 and 20. The cyclic voltammetry, differential pulse voltammetry and impedance spectroscopy are used to investigate the electrochemical performance. It was noted that the peak current indicating the oxidation of ascorbic acid at 0.04 V, increased with the increase in the thickness of electrode or the number of printed layers. The higher current values and lower series resistance was measured for layers 10 and 20, indicating the ideal printed thickness of sensors for low power operation and easy interfacing with read out electronics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
