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    Electrical properties of CsPbX3 (X=Cl, Br) perovskite quantum dot/poly (HEMA) cryogel nanocomposites
    (Elsevier Science Sa, 2022) Bakay, Melahat Sevgül; Sarkaya, Koray; Çadırcı, Musa
    Quantum dot-filled polymer nanocomposites are recent of interest due to the improvement of the properties and possibility of use in diverse application areas. In this study, poly(HEMA) cryogels and CsPbCl3 and CsPbBr3 perovskite quantum dots were separately synthesized and then perovskite quantum dots/cryogel nanocomposites were formed for the first time. After comprehensive characterizations of the nanocomposites, the dielectric properties of those structures were studied using impedance spectroscopy. All characterization methods revealed the effective formation of the quantum dot/cryogel nanocomposites. The real part of the dielectric components of the nanocomposites decreased concerning the pure cryogel. For the CsPbCl3 quantum dots filled nanocomposites, the imaginary part of the dielectric component and the loss tangent parameter increased almost by the factors of similar to 1.8 and similar to 2.2, respectively. On the other hand, for the CsPbBr3 quantum dots filled cryogel, the imaginary part of the dielectric component and the loss tangent parameter values decreased by the factors of similar to 2.6 and similar to 2 respectively. The large dielectric losses in the case of CsPbCl3 quantum dot-based nanocomposite were attributed to the high existence of surface traps on the surface of the CsPbCl3 quantum dots.
  • Küçük Resim Yok
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    Increasing the efficiency of perovskite solar cells using Cs4CuSb2Cl12 quantum dots as an interface layer: A numerical study
    (Sage Publications Ltd, 2022) Çadırcı, Musa; Bakay, Melahat Sevgül
    Recently, the advantages of perovskite solar cells (PSCs) and a significant increase in power conversion efficiency (PCE) have played an essential role in the preference for these materials. Although different methods are used to increase PCE and reduce losses at the interfaces in PSCs, placing a new layer between the absorber/hole transfer layer (HTL) or between the absorber/electron transfer layer (ETL) stands out as one of the most common methods. In this study, considering stability, sustainability, mobility, and non-toxicity, Cs4CuSb2Cl12 (CCSC) perovskite quantum dots (PQDs) were preferred as the interface layer between absorber and HTL in CsPbI3 and formamidinium lead iodide (FAPI)-based PSC devices. While SnO2, Cu2O, and nickel were used as ETL, HTL, and back contact, respectively, CsPbI3 and FAPI perovskites were utilized as absorber materials separately. Simulations were conducted on Solar Cell Capacitance Simulator (SCAPS-1D) software and the current density (J) and voltage characteristics were compared. By choosing different interface layer thicknesses, different radiative recombination coefficients (RRCs), and different defect sites, the cell efficiency of the PQD interlayer solar cells were simulated. Simulations were also carried out using different series resistance (R-s) and different shunt resistance (R-sh) values to show the effect of parasitic losses on cell efficiency, and it was observed that device efficiency increased where R-s was low and R-sh was high. In addition, in FAPI-based structure, with the addition of a PQD layer between the absorber and HTL, it was observed that the short circuit current density increased from 17.6 mA/cm(2) to 25.67 mA/cm(2), while the cell efficiency increased by 30%. Furthermore, according to the results obtained using CsPbI3 as an absorber, adding a PQD layer between CsPbI3 and HTL increased the short circuit current density from 17.8 mA/cm(2) to 20.7 mA/cm(2) and cell efficiency by 16%. To sum up, these simulation results demonstrate that inserting a PQD layer between the absorber and HTL significantly enhances the efficiency and charge carrier capacity of solar cells.
  • Küçük Resim
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    Molecularly Imprinted Polymer Based Biosensor For Choline
    (2020) Polat, Tuğçe; Bakay, Melahat Sevgül; Denizli, Adil; Utku, Feride Şermin
    Biosensors are systems that can perform quantitative and/or qualitative analysis of substances in liquid or gasenvironment through their biological recognition sites and transform the acquired data into detectable signals.Biosensors are able to detect physical changes (i.e. as density, mass concentration, etc.) by means of recognitionsites and correlate them with electrical or optical quantities (i.e. current, voltage and impedance). In this study,three molecularly imprinted pencil graphite electrodes with differing numbers of choline recognition sites, at E-1M, E-3 M and E-5 M concentration, were used as electrochemical biosensors. An increase in choline receptorconcentration on the electrode surface was expected to correlate with an increase in PGE surface bound cholineand thus lead to electrical changes. The study was conducted in a three-electrode cell with Ag/AgCl as thereference electrode, platinum wire as the counter electrode and PGE as the working electrode. Cyclicvoltammetry and electrochemical impedance measurements were conducted in 10 mM phosphate buffer solutioncontaining 5mM K3[FeCN6]-3/-4redox pair. As expected, as increasing amount of choline was bound to thecomplementary recognition sites on choline imprinted electrodes, a correlating change in current, voltage andimpedance was observed. The dynamic detection range for choline expanded as the choline concentrationimprinted on the electrodes increased. Using the E-1 M PGE electrode, 72 pM limit of detection, up to 7.2 nMlimit of linearity was attained.