Department of Physics

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Author: search.filters.author.Dr. Farah AlviSubject: search.filters.subject.FA17

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    Investigation of Doped (III-V) Group Elements Emissive Layer for Visible LED Applications
    (2019) Aqsa Hashmi; CIIT/FA17-RPH-043/LHR; Dr. Farah Alvi; LHR TP 5728
    This study Sb2S3 was prepared by applying hydrothermal technique with different concentration of Ag as a doping impurity to improve its optical and electrical properties to be used in optoelectronics for LED applications. FTIR spectra was used to analyze the vibrations of chemical bonds present in the different groups in the sample. The intensity of the peaks is reduced with the increase in doping concentration, this is because the strength of chemical bonds decreases because of intermolecular transition of groups present in the sample. Optical properties were studied by UV-Vis and PL spectroscopy. UV-vis spectra was used to calculate bandgap that comes out between 2.5-1.9 eV. The bandgap was reduced with the increase in doping concentration of Ag which indicate its good compatibility for LED applications. IV measurements were used to analyze IV characteristics of the samples and to find out the turn on voltage of the device. SEM results were helpful in analyzing the surface morphology of the samples and measuring the particle size. The device was characterized by electroluminescence spectra which confirmed the red emission from LEDs having emissive layers of undoped and doped Sb2S3. So the materials have bright future for visibe LED applications.
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    Optical Investigation of N-acetyl-L Capped Core- Shell Sb2Se3/ZnS Nanowires for Visible LED Application
    (Library Information Services, COMSATS University Islamabad, Lahore Campus, 2019) Muhammad Ejaz Dildar; CIIT/FA16-RPH-025/LHR; Dr. Farah Alvi; LHR TP 5707
    Light emitting diodes have always gained high interest to their potential for high efficiency lighting. Fabrication of Sb2Se3/ZnS core- shell nanowire LED is reported for first time. In this report Sb2Se3/ZnS core-shell nanowire synthesis by hydrothermal method and this composition was spin coated on FTO substrates to make thin films. UV visible spectroscopy, Photoluminescence spectroscopy and X-ray diffraction techniques were used to characterized thin films of Sb2Se3/ZnS core-shell composition. UV visible spectroscopy showed that the absorption spectrum of Sb2Se3/ZnS core-shell thin films was in UV region and photoluminescence spectroscopy showed that the emission spectrum is in visible and infra-red region. X-ray diffraction (XRD) was used to determine crystalline structure and phases within a solid. For device fabrication NiO and ZnO were used as hole transport layer and electron transport layer respectively. Sb2Se3/ZnS core-shell nanowires were sandwiched between hole transport layer and electron transport layer. Device was characterized by electroluminescence spectroscopy and IV measurements.