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  • Küçük Resim
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    Effects of CdTe Quantum Dot Dispersal on Current-Voltage Characteristics in Liquid Crystalline Mediums of E63, E7 and SCLP
    (2020) Kocakülah, Gülsüm; Kahyaoğlu, Aliye; Yıldırım, Mert; Köysal, Oğuz
    The usage of nano-sized quantum dots (QDs) particularly in guest-host based hybrid mediums revealedenhancements in electro-optical properties of the mediums, therefore the focus of considerable amount ofcontemporary studies has been about dispersal of QDs for improvements in medium. This study investigates theeffects of CdTe QD dispersal on current-voltage characteristics of some liquid crystalline materials such as E63,E7 and SCLP. Current is increased for all samples due to QD dispersal, however the best improvement is obtainedfor E7. Hence, current-voltage characteristics of E7 and QD dispersed E7 mediums were also investigated underUV light exposure. Current values of both mediums were found to increase with increasing UV light power dueto generation of electron-hole pairs. Photocurrent’s dependence on light power revealed that QD dispersal doesnot affect recombination mechanism in the medium. On the other hand, UV light responsivity of QD dispersed E7was obtained approximately twice of that of E7. Thus, it was concluded that CdTe QDs make considerablecontribution to current-voltage and photoconductivity characteristics of E7 in dark and under UV lightillumination.
  • Küçük Resim
    Öğe
    Influence of azo dye concentration on dielectric response in polymer dispersed liquid crystal composites
    (Elsevier, 2019) Önsal, Gülnür; Kocakülah, Gülsüm; Kahyaoğlu, Aliye; Köysal, Oğuz
    In this paper, we have investigated dielectric properties of azo dye methyl red (MR) doped polymer dispersed liquid crystal (PDLC) composites. Norland optical adhesive (NOA 65) and nematic liquid crystal (E63) materials were used to construction of PDLC composite. In order to observe the effect of MR concentration, PDLC was dispersed with 1,3 and 5% wt/wt MR Dielectric properties have been investigated using the dielectric spectroscopy method in the frequency range of 500 Hz to 10 MHz at room temperature. Dielectric constant (epsilon' and epsilon ''), dielectric anisotropy (Delta epsilon'), relaxation frequency (f(R)), relaxation time (tau), threshold voltage (V-th) and also splay elastic constant (K-11) have been determined for the pure PDLC and its doped version PDLC + 1%MR, PDLC + 3% MR and PDLC + 5% MR composites by using experimental data. Dispersal of increasing MR concentration caused tau, V-th, K-11 are decreased whereas f(R) is increased for the investigated samples. Results show that different MR concentrations significantly affect the dielectric properties of PDLC composites and make it suitable to design new based on PDLC device applications. (C) 2019 Elsevier B.V. All rights reserved.