Browsing by Author "Torlak, Yasemin"

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Citation - WoS: 13
Citation - Scopus: 13
Electrical Behaviors of the Co- and Ni-Based Poms Interlayered Schottky Photodetector Devices
(Wiley, 2022) Yıldırım, Murat; Kocyigit, Adem; Torlak, Yasemin; Yenel, Esma; Hussaini, Ali Akbar; Kuş, Mahmut
Polyoxometalates (POMs) are attractive materials for various applications such as energy storage, catalysis and medicine. Here, Co and Ni-based POMs are chemically synthesized and characterized by X-ray diffractometer (XRD) and Fourier transform infrared spectroscopies (FT-IR) for structural characterization. While the morphological behaviors are analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM), the optical properties are investigated by UV-Vis spectrometer. Electrochemical characterizations are carried out by cyclic voltammetry to determine oxidation levels of the metal centers in the POMs. The CoPOM and NiPOM are inserted in between the Al metal and p-Si semiconductor to obtain Al/CoPOM/p-Si and Al/NiPOM/p-Si Schottky-type photodetector devices. Current-voltage (I-V) and current-transient (I-t) measurements are employed to understand the electrical properties of the Al/CoPOM/p-Si and Al/NiPOM/p-Si devices under dark and various light power intensities. The devices exhibit phototransistor like I-V characteristics in forward biases due to having POMs active layers. Various device parameters are extracted from the I-V measurements and discussed in details. I-t measurements are performed to determine various detector parameters such as responsivity and specific detectivity values for under 2 V and zero biases. The Al/CoPOM/p-Si and Al/NiPOM/p-Si Schottky-type photodetector devices can be employed in optoelectronic applications.
Citation - WoS: 2
Citation - Scopus: 2
Polyoxometalate-Doped Hole Transport Layer To Boost Performance of Mapbi3-Based Inverted-Type Perovskite Solar Cells
(Amer Chemical Soc, 2025) Buyukcelebi, Sumeyra; Kazici, Mehmet; Torlak, Yasemin; Kus, Mahmut; Ersoz, Mustafa
This study delves into the examination of the efficiency, stability, and repeatability of perovskite solar cells (PSCs), a focal point in contemporary photovoltaic (PV) technologies. The aim is to address the challenges encountered in PSCs. To achieve this goal, Ge-doped polyoxometalate, a structure of significance in recent molecular electronics, was employed as a dopant in the hole transport layer (HTL). The study investigated alterations in the conductivity, improvements in efficiency, and changes in PV parameters. The utilization of PEDOT/PSS doped with a maximum of 2% GePOM resulted in an average efficiency increase of 27% in PSCs compared with the reference. Moreover, enhancements in stability and repeatability were also noted. Comparatively, the reference PSC operated at an efficiency of 11.18%, while PSCs incorporating 2% GePOM into PEDOT/PSS as the HTL exhibited a notable increase in the efficiency, reaching 14.22%. Furthermore, the champion device exhibited an observed fill factor value of 0.74, a short-circuit current density (J sc) value of 19.78 mA/cm2, and an open-circuit voltage (V oc) value of 0.98 V. Consequently, noteworthy enhancements have been noticed in the PV parameters of PSCs with the introduction of GePOM doping.
Citation - WoS: 5
Citation - Scopus: 6
Self-Powered Narrowband Near-Infrared Photodetector Based on Polyoxometalate Compound
(Elsevier, 2025) Hussaini, Ali Akbar; Torlak, Yasemin; Buyukcelebi, Sumeyra; Kus, Mahmut; Yildirim, Murat
Narrowband photodetectors are employed in optical communication, where designated wavelengths are used to transmit data, and in environmental sensing to identify specific gases that absorb distinct wavelengths of light. In this study, we developed a novel polyoxometalate compound for application as a near-infrared (NIR) photodetector. Li6 [alpha-P2W18O62]-.28H2O compound was synthesized successfully and was characterized using 31P NMR, FT-IR, UV-Vis, C-V, SEM, TEM, and AFM. We used Li6 [alpha-P2W18O62]-.28H2O compound as interlayer in Schottky type photodetector structure. Photodiode and photodetector measurements were performed under various solar intensities (20, 40, 60, 80, and 100 mW), ultraviolet, visible, and near-infrared wavelengths ranging from 351 to 1600 nm. Notably, the device exhibited an excellent responsivity, external quantum efficiency, and detectivity under near-infrared wavelengths. It showed 64.17 mA/W responsivity, 4.34 x 1010 Jones detectivity and 7.96 % external quantum efficiency at 1000 nm and 0 bias voltage. Moreover, the device demonstrated 4.736 A/W responsivity and 8.57 x 1011 Jones detectivity under solar light. Furthermore, this research introduces a novel compound for developing narrowband photodetectors utilizing polyoxometalate.
Citation - WoS: 10
Citation - Scopus: 10
W- and Mo-Based Polyoxometalates (pom) as Interlayer in Al/N-si Photodiodes
(SPRINGER, 2021) Yenel, Esma; Torlak, Yasemin; Koçyiğit, Adem; Erden, İbrahim; Kuş, Mahmut; Yıldırım, Murat
W- and Mo-based POM layers were fabricated by a chemical method successfully. The FT-IR and NMR spectrometer were performed to obtain structural behaviors of the W- and Mo-based POMs. SEM and AFM image used to reveal the surface morphologies of the W- and Mo-based POMs. The pinhole and crack-free porous surfaces were obtained. Electrochemical behaviors of the W- and Mo-based POMs were studied a galvanostat. Then, the W- and Mo-based POM layers used as film layer between the Al and n-Si layer to obtain POM interlayered photodiodes Thus, the Al/n-Si (reference), Al/WPOM/n-Si and Al/MoPOM/n-Si photodiodes were fabricated by evaporating of the metallic and ohmic contact in a thermal evaporator. I-V measurements were performed on the photodiodes under dark and various light illumination intensities. The photodiodes exhibited good rectifying properties, but rectifying behavior decreased with POM interlayers and increasing light power intensity. The reverse currents of the Al/n-Si photodiode increased almost 1000 times at 100 mW/cm(2). However, they increased almost 100 times for the Al/WPOM/n-Si and Al/MoPOM/n-Si photodiodes. Whereas the forward currents did not change for Al/n-Si photodiode, they increased with increasing light power in the case of Al/WPOM/n-Si and Al/MoPOM/n-Si photodiodes. Various diode parameters such as ideality factor, barrier height and series resistance values were calculated by various techniques and discussed in details. The detector parameters such as responsivity, photosensitivity and specific detectivity values were accounted and compared for the Al/n-Si, Al/WPOM/n-Si and Al/MoPOM/n-Si photodiodes with increasing light power. The POM interlayered photodiodes and photodetectors can be improved for industrial applications.