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    Investigation of photodetector performance based on methylammonium lead halide perovskites/reduced graphene oxide heterostructure
    (Springer, 2023) Jaf, Hawre Azad Othman; Pakma, Osman; Ozden, Sadan; Kariper, I. Afsin; Korkmaz, Satiye; Guneser, M. Tahir
    The remarkable advancements achieved in the field of perovskite materials have spurred the development of photodetectors, playing a pivotal role in diverse optoelectronic applications. Among these, heterostructured perovskite-based photodetectors have emerged as a superior choice, surpassing the performance capabilities of their pure perovskite counterparts. This study presents the fabrication of an rGO/MAPbI3 heterostructured photodetector via the spin-coating technique. A comprehensive structural analysis of the device was conducted, encompassing X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Current-voltage (I-V) and capacitance-voltage (C-V) measurements, performed under various illumination conditions as well as in the absence of light, unequivocally demonstrate the photodiode characteristics of the device. The data reveal a direct correlation between illumination intensity and both current and capacitance, substantiating the photodetector's responsiveness. Notably, the calculated photosensitivity values S (%) of the Al/Gra/p-Si device, measured under a reverse bias of - 2 V, exhibit a range, varying from 42,000 to 79,300%. Furthermore, observations suggest a decrease in series resistance with increasing illumination intensity, while the ideality factor and barrier height values show an opposite trend. In addition, frequency-dependent measurements divulge a decrease in capacitance as the frequency escalates. These findings can be elucidated through the interactions involving light-induced charges at the interface between the rGO oxide layer and the semiconductor, coupled with the dynamic fluctuations in quasi-Fermi levels within the state of equilibrium.
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    Optical properties of selenium sulfide thin film produced via chemical dropping method
    (Springer, 2018) Kariper, I. Afsin; Ozden, Sadan; Tezel, Fatma Meydaneri
    This paper describes the production of selenium sulfide (SeS2) crystalline thin film on commercial glass substrates, via chemical bath deposition. Transmittance, absorption, dielectric constant and refractive index of the produced films were investigated by UV/VIS Spectrum. It was found that changes occurred on the characteristics of the films and they were determined as a function of selenium sulfide concentration, which varied between 2x10(-3) and 5x10(-3)M. The structure of the film was analyzed using FTIR spectrum. The calculated refractive index values fell between 1.5 and 1.6, whereas the transmission ratio of the films was around 80-90%. Moreover, a peak in the reflectance was observed at 320-330nm for all investigated samples. The highest dielectric constant for the films was obtained at the deposition concentration of 0.005M. This study is believed to be useful for thin film production.