Effects of CdTe Quantum Dot Dispersal on Current-Voltage Characteristics in Liquid Crystalline Mediums of E63, E7 and SCLP

The usage of nano-sized quantum dots (QDs) particularly in guest-host based hybrid mediums revealed enhancements in electro-optical properties of the mediums, therefore the focus of considerable amount of contemporary studies has been about dispersal of QDs for improvements in medium. This study investigates the effects 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 obtained for E7. Hence, current-voltage characteristics of E7 and QD dispersed E7 mediums were also investigated under UV light exposure. Current values of both mediums were found to increase with increasing UV light power due to generation of electron-hole pairs. Photocurrent’s dependence on light power revealed that QD dispersal does not affect recombination mechanism in the medium. On the other hand, UV light responsivity of QD dispersed E7 was obtained approximately twice of that of E7. Thus, it was concluded that CdTe QDs make considerable contribution to current-voltage and photoconductivity characteristics of E7 in dark and under UV light illumination

PCDTBT:PCBM Tabanlı Organik Schottky Diyotlarının ve Heteroeklem Güneş Hücrelerinin Optoelektronik Karakterizasyonu

Bu çalışmada Gümüş/n-tipi Silisyum/poly[N-9′-heptadecanyl-2,7–carbazole–alt-5,5-(4′,7′-di–2–thienyl-2′,1′,3′-benzothiadiazole:[6,6]-phenyl-C61-butyric acid methyl ester/Altın (Ag/n-Si/PCDTBT:PC61BM/Au) organik metal-polimer yarıiletken Schottky bariyer diyotları, polimer arayüz olarak %20 PCDTBT ve %80 PCBM karışımı kullanılarak üretilmiştir. Üretilen diyotların 240 - 350 K sıcaklık aralığında akım-voltaj ölçümleri yapılarak, bu sıcaklıklardaki diyot idealite faktörü değerlerinin 1,80 ve 2,26 aralığında değiştiği gözlemlenmiştir. Çalışmanın ikinci aşamasında, İndiyum Kalay Oksit/PCDTBT:PCBM/Gümüş (ITO/PCDTBT:PCBM/Ag) organik güneş hücresi %20:%80 PCDTBT:PCBM hacimsel oranına sahip olacak şekilde üretilmiş ve güç dönüştürme verimi % 0,85 olarak bulunmuştur

Enhancement of electro-optical and dielectric properties of CdSeS/ZnS semiconductor quantum-dot-doped nematic liquid crystals in the presence of UV-illumination effect

WOS: 000468869000009In this study, we have investigated ultraviolet (UV) illumination effect on electro-optical and dielectric properties of varying concentration of CdSeS/ZnS semiconductor quantum-dot-doped 5CB nematic liquid crystal. Dielectric measurements were made from 10kHz to 10MHz frequency ranges in dark and under UV-illumination conditions. Electro-optical measurements were also performed with a voltage-dependence light transmission system at 10kHz frequency in dark and under UV-illumination conditions. Significant physical parameters such as relaxation frequency (f(R)), real and imaginary components of complex dielectric permittivity (epsilon and epsilon), and threshold voltage (V-th) values were obtained from experimental results. Results show that UV-illumination effects cause considerable improvements on electro-optical and dielectric characteristic of investigated samples.Duzce University Scientific Research ProjectDuzce University [2018.05.02.811]This work supported financially by Duzce University Scientific Research Project (Project No: 2018.05.02.811)

Investigation of photo-induced change of electro-optical performance in a liquid crystal-organic field effect transistor (LC-OFET)

WOS: 000380160400004This study aimed to improve the electrical characteristics of poly(3-hexylthiophene) (P3HT) and liquid crystal-organic field effect transistors (LC-OFETs) under UV illumination. Consequently, a novel LC-OFET was fabricated using a nematic liquid crystal (E63) and a P3HT mixture in an OFET cell. Cell thickness was determined through field emission scanning electron microscopy. For assessment of the electrical characteristics, the LC-OFET device was exposed to various UV light intensities in total darkness for the purpose of obtaining the output- and transfer-current voltage. The capacitance-frequency plot of the capacitor cell was then measured to determine the main parameters including the threshold voltage (V-Th), field effect mobility ((FET)) and current on/off ratio (I-on/off) of the device. Thus, the full characterisation and UV light response of the electronic parameters were determined for this new class of transistors. Results showed that the new LC-OFET exhibited good performance in the form of low V-Th, high(FET), and high I-on/off.Duzce University Scientific Research ProjectsDuzce University [2016.05.02.411]This work was supported by the Duzce University Scientific Research Projects [Project number 2016.05.02.411]

Effect of frequency on dielectric properties of liquid crystal doped with side-chain liquid crystalline polymer

Gokcen, Muharrem/0000-0001-9063-3028WOS: 000294092500076The frequency and applied bias voltage dependence of the dielectric properties and dielectric anisotropy of liquid crystal (LC) doped with side-chain liquid crystalline polymer (SLCP) mixture have been investigated using the admittance spectroscopy method (C-V and G/omega-V) in the frequency range of 10 kHz to 10 MHz at room temperature. The liquid crystal used in this experiment is E63. The doping material used in this study is SLCP and its concentration is ensured 1 wt % in E63. Dielectric constant (epsilon'), dielectric loss (epsilon), dielectric loss tangent (tan delta) and real and imaginary parts of electrical modulus (M' and M '') of the E63/SLCP mixture was also calculated. Moreover, dielectric anisotropy (Delta epsilon) as a function of frequency was obtained. Results show that the values of the all dielectric parameters are strong functions of frequency and applied bias voltage. After a critical frequency, dielectric anisotropy has negative values according to p/n type changing. (C) 2011 Elsevier B.V. All rights reserved

Determination of Phase Transition and Electro-optical Behaviors of Quantum Dot Doped Polymer Dispersed Liquid Crystal

This paper describes our research into phase transition, electro-optical and dielectric behaviors of polymer dispersed liquid crystal (PDLC) and cadmium selenide sulphide/zinc sulphide quantum dot (QD) doped PDLC (PDLC/QD). The PDLC was prepared with nematic liquid crystal (E63) and UV-curable photopolymer (NOA65) by using a polymerization induced phase separation technique. Dielectric properties of composites were investigated with a dielectric/impedance analyzer at 1 kHz–10 MHz frequency range. Electro-optical measurements of investigated samples were carried out using an electro-optical switching method. Phase transition temperature of PDLC and PDLC/QD composites was also determined, using a differential scanning calorimeter. The results showed that the introduction of QD significantly changes the physical properties of PDLC, and these changes could become a focus of interest for future applications. © 2020, The Minerals, Metals & Materials Society

Effect of intermolecular charge transfer between Ni(II)Pc and CdSeS/ZnS QD on dielectric relaxation mechanism of 5CB nematic liquid crystals in the presence of UV illumination

WOS: 000512889300085This paper is a report on electro-optical and dielectric parameters of Ni(II)Pc (nickel(II) phthalocyanine) and CdSeS/ZnS (cadmium selenide sulfide/zinc sulfide) quantum dot (QD) doped 5CB (4-pentyl-4 '-cyanobiphenyl) nematic liquid crystal (LC) in the dark and under UV illumination condition. Electro-optical and dielectric measurements of the samples were carried out using electro-optical switching and dielectric spectroscopy methods, respectively. Dielectric anisotropy, relaxation frequency, dielectric strength, and threshold voltage values were determined using the experimental data. Investigation of dielectric properties demonstrates that relaxation frequency is decreased because of the dispersal of Ni(II)Pc and CdSeS/ZnS QD under UV exposure. The electro-optical investigation also shows that UV illumination and dispersal of Ni(II)Pc and CdSeS/ZnS QD cause a decrease in threshold voltages. Overall, results indicate that Ni(II)Pc, CdSeS/ZnS QD and UV light enhanced the electro-optical and dielectric properties of 5CB nematic LC

CdSeS/ZnS Kuantum Nokta Katkılı 5CB Nematik Sıvı Kristalinde Optik Bant Aralıklarının İncelenmesi

Bu çalışmada, CdSeS/ZnS alaşım kuantum nokta katkılı 5CB (4-pentyl-4′-cyanobiphenyl) nematik sıvı kristal yapının optik bant aralığı değerleri incelenmiştir. CdSeS/ZnS alaşım kuantum nokta, 5CB nematik sıvı kristal yapı içerisine ağırlıkça % 0,05, % 0,1 ve % 0,15 oranlarında katkılanarak optik bant aralığı değerleri elde edilmiştir. Deneysel sonuçlara göre kuantum nokta katkılanmasıyla optik bant aralığı değerlerinin azaldığı gözlemlenmiştir. Elde edilen sonuçlar, CdSeS/ZnS alaşım kuantum nokta yapının sıvı kristal tabanlı cihaz uygulamalarında elektro-optik özellikleri değiştirebilen alternatif bir malzeme olarak kullanılabileceğini göstermektedir

The Fe3O4 nanoparticle doping effect in liquid crystal on electrical and dielectric properties

Gokcen, Muharrem/0000-0001-9063-3028; YILDIRIM, Mert/0000-0002-8526-1802WOS: 000318784500009Fe3O4 nanoparticles were doped into E63 coded liquid crystal (LC) with 0.1 wt% to investigate the effect of Fe3O4 on the electrical and dielectric properties of LC in a wide range of frequency, bias voltage, and illumination. The frequency, bias voltage, and illumination level dependence of the electrical and dielectric properties of pure E63 and doped mixture (E63-Fe3O4) has been investigated using the current-voltage (I-V) and admittance spectroscopy (C-V and G/omega-V) data in the frequency range of 10 kHz - 1 MHz at room temperature. Results show that the increment in current with Fe3O4 doping is due to the metallic nature of the Fe3O4 nanoparticles. The current switching voltage of reorientation is shifted to lower voltage values as a result of Fe3O4 doping. Same behavior is also observed with increasing illumination level. The polarization contribution of Fe3O4 doping is evident considering the values of Delta epsilon' = epsilon'(E63/Fe3O4) - epsilon'(E63) at low frequencies. Moreover, depending on the existence of Fe3O4 doping agent, there is a split in sigma(ac)-f plots where sigma(ac) values increase with frequency, especially at high frequencies.Duzce UniversityDuzce University [2011.05.02.073, 2012.05.02.110]This work is supported by Duzce University Scientific Research Projects (project nos. 2011.05.02.073 and 2012.05.02.110)

Investigation of Optical Band Gap of CdSeS/ZnS Quantum Dot Doped 5CB Nematic Liquid Crystals

Bu çalışmada, CdSeS/ZnS alaşım kuantum nokta katkılı 5CB (4-pentyl-4?-cyanobiphenyl) nematik sıvı kristal yapının optik bant aralığı değerleri incelenmiştir. CdSeS/ZnS alaşım kuantum nokta, 5CB nematik sıvı kristal yapı içerisine ağırlıkça % 0,05, % 0,1 ve % 0,15 oranlarında katkılanarak optik bant aralığı değerleri elde edilmiştir. Deneysel sonuçlara göre kuantum nokta katkılanmasıyla optik bant aralığı değerlerinin azaldığı gözlemlenmiştir. Elde edilen sonuçlar, CdSeS/ZnS alaşım kuantum nokta yapının sıvı kristal tabanlı cihaz uygulamalarında elektrooptik özellikleri değiştirebilen alternatif bir malzeme olarak kullanılabileceğini göstermektedirIn this study, optical band gap values of 5CB (4-pentyl-4 'cyanobiphenyl) nematic liquid crystal structure doped with CdSeS/ZnS alloyed quantum dots are investigated. The CdSeS/ZnS alloyed quantum dot was doped into the 5CB nematic liquid crystal structure at 0.05, 0.1 and 0.15 % wt/wt and optical band gap values were obtained. According to experimental results, optical band gap values decrease with quantum dot doping. The results show that the CdSeS/ZnS alloyed quantum dots can be alternative materials used in liquid crystal based device applications whose electro-optical properties are able to be easily modifie