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    Wyświetlanie 1-8 z 8
    Tytuł:
    Numerical analysis of the compositional graded quaternary barrier AlGaN-based ultraviolet-C light-emitting diode
    Autorzy:
    Malik, S.
    Usman, Muhammad
    Hussain, M.
    Munsif, M.
    Khan, S.
    Rasheed, S.
    Ali, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818198.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    ultraviolet
    light-emitting diodes
    efficiency
    quantum wells
    Opis:
    The compositional graded quaternary barriers (GQBs) instead of ternary/conventional quantum barriers (QBs) have been used to numerically enhance the efficiency of AlGaN-based ultraviolet light-emitting diode (LED). The performance of LED with GQBs is examined through carrier concentrations, energy band diagrams, radiative recombination, electron and hole flux, internal quantum efficiency (IQE), and emission spectrum. As a function of the operating current density, a considerable reduction in efficiency droop is observed in the device with composition-graded quaternary barriers as compared to the conventional structure. The efficiency droop in case of a conventional LED is ~77% which decreased to ~33% in case of the proposed structure. Moreover, the concentration of electrons and holes across the active region in case of the proposed structure is increased to ~156% and ~44%, respectively
    Źródło:
    Opto-Electronics Review; 2021, 29, 3; 80--84
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structure equation as novel strategy for optimum reflector design
    Autorzy:
    Ou, Chung-Jen
    Powiązania:
    https://bibliotekanauki.pl/articles/174423.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    illumination design
    light-emitting diodes
    structure equation
    Opis:
    The optimal use of energy resources is the central dogma for green technology and bio-optics. Reflectors provide a simple and fundamental structure for energy transport from a light emitting diode (LED) chip, and an appropriately designed reflector can reduce the fabrication cost of secondary optics for the LED. This paper demonstrates the role of three proposed reflector geometric factors in the two performance metrics – uniformity and collected energy (power), for designing LED reflectors. Through canonical factor analysis, a linear structure equation for LED reflector is suggested, and the methodology for designing the optimal shape is discussed. In addition, a generalized factor and a synthesis response are proposed for a more comprehensive investigation of optical performance. Results indicate a key parameter for balancing the optical performance, and the effects of various parameters and the trade-offs are revealed.
    Źródło:
    Optica Applicata; 2020, 50, 1; 95-110
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical analysis of the compositional graded quaternary barrier AlGaN-based ultraviolet-C light-emitting diode
    Autorzy:
    Malik, S.
    Usman, Muhammad
    Hussain, M.
    Munsif, M.
    Khan, S.
    Rasheed, S.
    Ali, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1818193.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    ultraviolet
    light-emitting diodes
    efficiency
    quantum wells
    Opis:
    The compositional graded quaternary barriers (GQBs) instead of ternary/conventional quantum barriers (QBs) have been used to numerically enhance the efficiency of AlGaN-based ultraviolet light-emitting diode (LED). The performance of LED with GQBs is examined through carrier concentrations, energy band diagrams, radiative recombination, electron and hole flux, internal quantum efficiency (IQE), and emission spectrum. As a function of the operating current density, a considerable reduction in efficiency droop is observed in the device with composition-graded quaternary barriers as compared to the conventional structure. The efficiency droop in case of a conventional LED is ~77% which decreased to ~33% in case of the proposed structure. Moreover, the concentration of electrons and holes across the active region in case of the proposed structure is increased to ~156% and ~44%, respectively.
    Źródło:
    Opto-Electronics Review; 2021, 29, 3; 80--84
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Design of LED collimator for uniform illumination using two freeform lenses
    Autorzy:
    Zeng, J.
    Li, X.
    Ge, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/173429.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    illumination design
    lenses
    light-emitting diodes
    optical design
    high uniformity
    Opis:
    Regulating the illuminance distribution of an LED collimator to produce a uniform illumination in both the near field and the far field is a challenge in illumination design. In this paper, we present an effective method for designing two separated freeform lenses to control the illuminance distribution and the direction of the rays from the LED. The first lens redistributes the ray energy, and the second one collimates them to obtain a uniform collimated illumination. According to the conservation law of energy, Snell’s law, Fermat’s law and tangent-plane iterative method, the two freeform surfaces could be calculated simultaneously. The simulation results show that the two freeform lenses can control most of rays into an angle within ±1.5° for an LED with 1 × 1 mm size. The illuminance uniformities are higher than 0.9 in both the near field and the far field.
    Źródło:
    Optica Applicata; 2018, 48, 3; 413-420
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Effect of Light-Emitting Diodes Illumination Period and Light Intensity on High Rate Algal Reactor System in Laundry Wastewater Treatment
    Autorzy:
    Tangahu, B. V.
    Triatmojo, A.
    Purwanti, I. F.
    Kurniawan, S. B.
    Powiązania:
    https://bibliotekanauki.pl/articles/123276.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    algae
    Chlorella vulgaris
    laundry wastewater
    illumination period
    light-emitting diodes
    light intensity
    microalgae
    Opis:
    Wastewater that contains high concentration of nutrients can create instability in water ecosystem if left untreated. Laundry wastewater contains nutrients in high concentration. The nutrients that commonly found in laundry wastewater are nitrogen and phosphorus. This study had a purpose to determine the effect of illumination period and light intensity for the removal of Chemical Oxygen Demand (COD), Nitrogen-ammonia (NH3-N), and phosphate (P) content using Chlorella vulgaris in High Rate Algal Reactor (HRAR) treatment. Variables that used were exposure period of 12 and 24 hours and light intensity of 2000–3000 Lux, 4000–5000 Lux, and 6000–7000 lux. The parameters tested to determine the efficiency of nutrient removal were COD, Nitrogen-ammonia, phosphate and Chlorophyll α to determine the condition of algae development. The results showed that the highest nutrient removal were obtained by the reactor with 24 hours illumination period with light intensity of 6000–7000 Lux that was capable of removing 54.63% of COD, and 22.15% of P. The 12-hour illumination period was better in terms of NH3-N removal, up to 50.07%. On the basis of the of statistic test result, the illumination period did not significantly influence the removal efficiency of COD, NH3-N and P indicated by P-value >0.05, while the light intensity significantly affect the removal of COD and NH3-N showed by P value <0.05.
    Źródło:
    Journal of Ecological Engineering; 2018, 19, 6; 170-175
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Diody LED - odpady niebezpieczne dla środowiska
    LED diodes - environmentally hazardous waste
    Autorzy:
    Sokołowska, W.
    Karaś, A.
    Zalewska, I.
    Harasimowicz-Siemko, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/192226.pdf
    Data publikacji:
    2011
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Technologii Materiałów Elektronicznych
    Tematy:
    dioda LED
    ICP-OES
    FAAS
    ochrona środowiska
    recykling
    light-emitting diodes
    environmental protection
    recycling
    Opis:
    W Laboratorium Charakteryzacji Materiałów Wysokiej Czystości ITME przeprowadzono analizę składu chemicznego kilku rodzajów diod LED obecnych na polskim rynku [2]. Omówiono zawartość metali kancerogennych oraz metali niebezpiecznych dla środowiska . Porównano je z rezultatami uzyskanymi w UCI (Uniwersytet Kalifornia) opisanymi w [1] i normami TTCL.
    An analysis of the chemical composition of several types of light-emitting diodes available on the Polish market was conducted in the Department of High Purity Materials Characterization of ITME [2]. In the course of the analysis, the content of carcinogenic metals and environmentally hazardous metals was explored. The findings were compared with the results achieved at the University of California, Irvine, described in [1], and with TTCL standards.
    Źródło:
    Materiały Elektroniczne; 2011, T. 39, nr 2, 2; 23-26
    0209-0058
    Pojawia się w:
    Materiały Elektroniczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    C,N-cyklometalowane kompleksy irydu(III) : wydajne emitery fosforescencyjne dla organicznych diod elektroluminescencyjnych (OLED). Cz. 1 i 2
    C,N-cyclometalated iridium(III) complexes : efficient phosphorescent emitters for organic electroluminescent diodes (OLED). Part 1 and 2
    Autorzy:
    Orwat, Bartosz
    Kownacki, Ireneusz
    Powiązania:
    https://bibliotekanauki.pl/articles/1413294.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    emitery fosforescencyjne
    diody elektroluminescencyjne
    kompleksy irydu(III)
    phosphorescent emitters
    light-emitting diodes
    iridium(III) complexes
    Opis:
    Organic electroluminescent panels have been widely available on the commercial market for several years, in the form of screens used in mobile phones, tablets, and TV sets. The display panels are produced in RGB technology, in which iridium(III) coordination compounds act as phosphorescent emitters of red and green light. Because of their high emission quantum efficiency and stability, the emitters containing 2-phenylpyridinato ligands and their derivatives have proved to be particularly useful. An interesting issue was the contrast between an extensive state of knowledge on the abovementioned compounds and a poor state of knowledge on analogous iridium(III) complexes equipped with benzo[h]quinolinato ligands. Application of the latter seemed interesting because of the similar size of benzo[h]quinoline and 2-phenylpyridine coordination pockets, but much more rigid structure and a greater degree of conjugation of the former, which could have a significant impact on the properties of complexes equipped with this type of ligand. Regarding to the above, this dissertation concerns the subject of the design and synthesis of new iridium(III) coordination compounds equipped with a benzo[h]quinoline motif, as well as the analysis of the structural changes impact on the photophysical, electroluminescent, thermal, electrochemical and spectroscopic properties of selected classes of compounds targeted for the application in OLED technology. Accordingly, the article presents the results of studies on two classes of heteroleptic of C,N-cyclometalated iridium(III) complexes, namely, of the salt type with the general formula [Ir(bzq)2(N^N)]+A-, stabilized by structurally different N,N-donating ligands, as well as neutral coordination compounds of the type [Ir(bzq)2(N^O)], bearing N,O-donating ß-ketoiminato ligands in the structure equipped with aryl moieties of various structure. The work included research on the determination of the correlation between the structure of ancillary ligand introduced into the coordination sphere of the metal and the above-mentioned properties. Additionally, based on the results of quantum-chemical calculations, work was undertaken to develop synthetic pathways enabling the incorporation to the C,N-cyclometalating benzo[h]quinoline ligand of substituents characterized by different stereo-electronic properties, enabling the modification of the emission parameters of the target complexes. In the next phase of research, the functionalized precursors of the bzq ligand were successfully used in the synthesis of binuclear complexes, key reagents in the preparation of corresponding mononuclear iridium coordination derivatives with electroluminescent properties.
    Źródło:
    Wiadomości Chemiczne; 2021, 75, 1-2; 163-231
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spectrally tunable light source based on light-emitting diodes for custom lighting solutions
    Autorzy:
    Burgos-Fernandez, F. J.
    Vilaseca, M.
    Perales, E.
    Herrera-Ramirez, J. A.
    Martinez-Verdu, F. M.
    Pujol, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/173803.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    solid state lighting
    light-emitting diodes
    CIE standard illuminants
    minimization algorithm
    customized lighting design
    radiometry
    Opis:
    This study describes a novel spectral LED-based tunable light source used for customized lighting solutions, especially for the reconstruction of CIE (Commission Internationale de l'Eclairage) standard illuminants. The light source comprises 31 spectral bands ranging from 400 to 700 nm, an integrating cube and a control board with a 16-bit resolution. A minimization algorithm to calculate the weighting values for each channel was applied to reproduce illuminants with precision. The differences in spectral fitting and colorimetric parameters showed that the reconstructed spectra were comparable to the standard, especially for the D65, D50, A and E illuminants. Accurate results were also obtained for illuminants with narrow peaks such as fluorescents (F2 and F11) and a high-pressure sodium lamp (HP1). In conclusion, the developed spectral LED-based light source and the minimization algorithm are able to reproduce any CIE standard illuminants with a high spectral and colorimetric accuracy able to advance available custom lighting systems useful in the industry and other fields such as museum lighting.
    Źródło:
    Optica Applicata; 2016, 46, 1; 117-129
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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