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electroluminescence
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Near-white emitting QD-LED based on hydrophilic CdS nanocrystals
, Article Journal of Luminescence ; Volume 132, Issue 2 , 2012 , Pages 467-473 ; 00222313 (ISSN) ; Marandi, M ; Saievar Iranizad, E ; Taghavinia, N ; Liu, B ; Sun, H. D ; Sun, X. W ; Sharif University of Technology
Abstract
In this work we report fabrication of a nanocrystal (NC)-based hybrid organicinorganic LED with structure of ITO/PEDOT:PSS/PVK/CdS-NCs/(Al or Mg:Ag). The hydrophilic CdS NCs were synthesized using a novel aqueous thermochemical method at 80 °C and sizes (around 2 nm) were controlled by thioglycolic acid (TGA) as the capping agent. The favorite feature of these NCs is their relatively high emission intensity and broad, near-white emission. The hydrophilic CdS NCs were successfully spin coated using Triton X-100 as the wetting agent. The fabricated LEDs demonstrated a turn on voltage about 7 V for Al metallic contact. The electroluminescence was a broad spectrum at 540 and 170 nm width, which...
Tunable Carbon–CsPbI3 Quantum Dots for White LEDs
, Article Advanced Optical Materials ; Volume 9, Issue 4 , 2021 ; 21951071 (ISSN) ; Gualdrón-Reyes, A. F ; Masi, S ; Ganji, B. A ; Taghavinia, N ; Gené-Marimon, S ; Palomares, E ; Mora Seró, I ; Sharif University of Technology
Wiley-VCH Verlag
2021
Abstract
In this work, a simple method to prepare white light emissive diodes based on quantum dot (QD) colloidal solutions using mixed carbon QDs (CQDs) and CsPbI3 perovskite (PQDs) is reported. The right combination generates emission across the entire visible spectrum upon ultraviolet excitation. The white light emission of the final films provides high and stable color rendering index of 92%, tuning the chromaticity coordinates of the emission through the applied voltage. By varying the CsPbI3 QD concentration, a mixture is obtained that emits the “warm”, “neutral”, and “cold” white light sought for many indoor lighting applications, or to approximate the visible region of the solar spectrum,...
Tunable Carbon–CsPbI3 quantum dots for white LEDs
, Article Advanced Optical Materials ; 2020 ; Gualdrón-Reyes, A. F ; Masi, S ; Ganji, B. A ; Taghavinia, N ; Gené-Marimon, S ; Palomares, E ; Mora Seró, I ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
In this work, a simple method to prepare white light emissive diodes based on quantum dot (QD) colloidal solutions using mixed carbon QDs (CQDs) and CsPbI3 perovskite (PQDs) is reported. The right combination generates emission across the entire visible spectrum upon ultraviolet excitation. The white light emission of the final films provides high and stable color rendering index of 92%, tuning the chromaticity coordinates of the emission through the applied voltage. By varying the CsPbI3 QD concentration, a mixture is obtained that emits the “warm”, “neutral”, and “cold” white light sought for many indoor lighting applications, or to approximate the visible region of the solar spectrum,...
When photoluminescence, electroluminescence, and open-circuit voltage diverge-light soaking and halide segregation in perovskite solar cells
, Article Journal of Materials Chemistry A ; Volume 9, Issue 24 , 2021 , Pages 13967-13978 ; 20507488 (ISSN) ; Yang, B ; Kim, Y ; Mohammadpour, R ; Taghavinia, N ; Hagfeldt, A ; Tress, W ; Sharif University of Technology
Royal Society of Chemistry
2021
Abstract
Perovskite solar cells suffer from various instabilities on all time scales. Some of them are driven by light, in particular when employing compounds with mixed halides. Such light soaking effects have been observed to result in performance changes of solar-cell devices. They have also been spectroscopically investigated in detail on films, where the formation of a low-gap iodine-rich phase, seen as a red shift of the PL, has been found to be responsible for a reduced open-circuit voltage. However, studies synchronously examining device performance and its relation to spectroscopy data are scarce. Here, we perform an in operando study, where we investigate the changes of open-circuit voltage...
Mechanochromic and thermally activated delayed fluorescence dyes obtained from D–A–D′ type, consisted of xanthen and carbazole derivatives as an emitter layer in organic light emitting diodes
, Article Chemical Engineering Journal ; Volume 430 , 2022 ; 13858947 (ISSN) ; Dashti, A ; Hosseinnezhad, M ; Rabiei, M ; Palevicius, A ; Doustmohammadi, A ; Janusas, G ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this study, we designed, engineered and investigated two new thermally activated delayed fluorescence (TADF) dyes obtained from D–A–D′ type, consisted of 2-(9H-carbazol-9-yl)-3-(3-methoxy-9H-carbazol-9-yl)-9H-xanthen and 2-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3-(3-methoxy -9H-carbazol-9-yl)-9H-xanthen. In these dyes, xanthen derivative and carbazole derivatives have played important roles as an acceptor and two unsymmetrical donor units. In addition, the photophysical properties of these dyes were evaluated by the UV–VIS absorption, photoluminescence spectroscopy and photoluminescence decay lifetime analysis in solution, initial dye, non-doped and doped solid state (neat–film) at...
Synthesis of CdS nanocrystals by a microwave activated method and investigation of the photoluminescence and electroluminescence properties
, Article Applied Surface Science ; Volume 257, Issue 23 , September , 2011 , Pages 9796-9801 ; 01694332 (ISSN) ; Iranizad, E. S ; Marandi, M ; Taghavinia, N ; Amrollahi, R ; Sharif University of Technology
2011
Abstract
We have synthesized CdS nanocrystals (NCs) by a microwave activated method. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The aqueous synthesis was based on the heat sensitivity of Na2S 2O3. In this method, microwave irradiation creates the activation energy for dissociation of Na2S2O3 and leads to the CdS NCs formation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses demonstrated hexagonal phase CdS NCs with an average size around 3 nm for sample prepared at 5 min irradiation time. A band gap range of 3.38-2.89 eV was possible only by increasing the microwave irradiation time, corresponding to a...