Browsing by Subject "Blue emission"
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Item Open Access Blue organic light-emitting diodes based on pyrazoline phenyl derivative(Elsevier, 2012-01-21) Stakhira, P.; Khomyak, S.; Cherpak, V.; Volyniuk, D.; Simokaitiene, J.; Tomkeviciene, A.; Kukhta, N.A.; Grazulevicius, J.V.; Kukhta, A.V.; Sun, X.W.; Demir, Hilmi Volkan; Hotra, Z.; Voznyak, L.The results of an experimental study of the electroluminescent device made of ITO/CuI/2,6-di-tert.-butyl-4-(2,5-diphenyl-3,4-dihydro-2H-pyrazol-3-yl)- phenol (HPhP)/3,6-Di(9-carbazolyl)-9-(2-ethylhexyl) carbazole (TCz1)/Ca:Al with efficacy up to 10.63 cd/A are presented. HPhP provides blue emission with a peak wavelength at 445 nm. The layer of TCz1 acts as an electron-transporting layer. In the framework of density functional theory (DFT) approach the geometry configuration and energy levels of HPhP are found being in a good agreement with spectral and cyclic voltammogram data.Item Open Access Blue-emitting CdSe nanoplatelets enabled by sulfur-alloyed heterostructures for light-emitting diodes with low turn-on voltage(American Chemical Society, 2021-12-28) İzmir, M.; Sharma, A.; Shendre, S.; Durmuşoğlu, E. G.; Sharma, V. K.; Shabani, Farzan; Baruj, Hamed Dehghanpour; Delikanlı, Savaş; Sharma, M.; Demir, Hilmi VolkanColloidal nanoplatelets (NPLs) have emerged as the last class of semiconductor nanocrystals for their potential optoelectronic applications. The heterostructures of these nanocrystals can achieve high photoluminescence quantum yield and enhanced photostability, along with color purity. Such advantages make them a promising candidate for solution-processable light-emitting diodes (LEDs). However, to date, blue-emitting CdSe nanoplatelets (NPLs) exhibit poor photoluminescence quantum yield and also typically suffer from a rolled-up morphology. To mitigate these problems in this work, we propose and demonstrate efficient alloyed 4 ML CdSe1–xSx nanoplatelets having a CdS crown with enhanced photoluminescence quantum yields (up to 60%) in the blue region (462–487 nm). We successfully used these NPLs as an electrically driven active emitter in the blue-emitting NPL-LEDs with a low turn-on voltage of ∼4 V. The Commission Internationale de L’Eclairage (CIE) coordinates of (0.23, 0.14) were obtained for these blue-emitting NPL-LEDs. These emitters could potentially open up the opportunity for full-color displays using these NPL-based blue LEDs in conjunction with the red and green ones.Item Open Access Synthesis of ultra-small Si / Ge semiconductor nano-particles using electrochemistry(Elsevier, 2012) Alkis, S.; Ghaffari, M.; Okyay, Ali KemalIn this paper, we describe the formation of colloidal Si/Ge semiconductor nano-particles by electrochemical etching of Ge quantum dots (GEDOT), Silicon-Germanium graded layers (GRADE) and Silicon-Germanium multi-quantum well (MQW) structures which are prepared on Silicon wafers using low pressure chemical vapor deposition (LPCVD) technique. The formation of Si/Ge nano-particles is verified by transmission electron microscope (TEM) images and photoluminescence (PL) measurements. The Si/Ge nano-particles obtained from GEDOT and GRADE structures, gave blue emissions, upon 250 nm, and 300 nm UV excitations. However, the nano-particles obtained from the MQW structure did exhibit various color emissions (orange, blue, green and red) upon excitation with 250 nm, 360 nm, 380 nm and 400 nm wavelength light.