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    Enhanced metal assisted etching method for high aspect ratio microstructures: Applications in silicon micropillar array solar cells
    (Pergamon-Elsevier Science Ltd, 2019) Baytemir, Gülşen; Ciftpinar, E. Hande; Turan, Rasit
    A solar cell device, fabricated on high density array cylindrical pillars, enables photogenerated carrier collection in the radial direction, thus shortening the path length of the carriers reaching the junction. It also provides advantages over conventional planar junction solar cells, such as reduced surface reflectance and enhanced light trapping. In this study, highly ordered Si micropillars were fabricated by photolithography and metal assisted etching (MAE) methods. It is shown that the use of ethanol as a solvent during the etching process and increasing HF concentration in the MAE solution both improve the quality of the surfaces of the pillars. Micropillars with smooth sidewalls and a high aspect ratio were obtained in this way. Solar cells with a radial junction were then fabricated on these micropillars. Standard doping, SiO2/SiNx passivation, and metallisation steps were carried out for the fabrication of solar cells with different micropillar lengths. A significant decrease in reflectance values was observed as the micropillar length increased, as expected. Solar cell short circuit current density (J(SC)) and efficiency (eta) of the solar cells tended to increase with micropillar length up to 11.5 mu m and then decrease due to increased surface recombination. The maximum efficiency achieved in this study is 17.26%.
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    A non-enzymatic electrochemical sensor based on polyaniline/borophene nanocomposites for dopamine detection
    (Springer Heidelberg, 2023) Baytemir, Gülşen
    Non-enzymatic electrochemical sensors are attractive because of their high sensitivity, rapid detection, low-cost and easy fabrication. Herein, a non-enzymatic electrochemical sensor based on Polyaniline/borophene nanocomposites for dopamine detection is presented. Borophene nanosheets were prepared using a clean and low-cost sonication method. The product was characterized by XRD, SEM, HRTEM and FTIR. Next, the PANI/borophene nanocomposite material was prepared and used to modify the PANI electrode for use in the detection of dopamine with cyclic voltammetry. The nanocomposite material presented the large peak currents indicating the nanocomposite reveals better electrochemical activity with the presence of borophene for dopamine detection in the concentration range of 0.15625-5 mu M. At a scan rate of 50 mV/s, the PANI-based sensor exhibited a sensitivity of 153.67 mu A mu M-1 cm(-2) with detection limit of 0.064 mu M, while the PANI/borophene nanocomposite-based sensor exhibited a sensitivity of 385.05 mu A mu M-1 cm(-2) with 0.017 mu M detection limit. Due to the excellent electrochemical performance obtained in this work, PANI/borophene nanocomposites could be a promising biosensor material for dopamine electrochemical analysis for biomedical applications.