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Öğe Morphological, structural and optical characteristics of graphene oxide layers and metal/interlayer/semiconductor photovoltaic diode application(National Institute of Research and Development for Optoelectronics, 2018) Güllü, Ömer; Çankaya, MuratThis work describes the optical, morphological and structural characterizations of graphene oxide (GO) layers grown by drop casting and annealing process. UV-vis optical measurement shows that the values of direct and indirect optical gap energy of the GO film are 3.89 eV and 3.21 eV, respectively. The graphene oxide (GO) layer has been placed in the metal/ interlayer /semiconductor (MIS) diodes (total 17 devices) on p-Si wafers. The graphene oxide diodes give a better barrier height enhancement as compared with the conventional diodes. The value of homogeneous barrier height for Al/GO/p-Si MIS junctions was extracted as 0.74 eV. The diodes were also investigated under 300 watt light illumination for photovoltaic applications. Additionally, interfacial properties of the MIS diode with GO interlayer were determined. It has been seen that the capacitance of the device changes as a function of gate voltage and signal frequency from the capacitance-frequency measurements. It has also been reported that the interfacial trap charges reduce the capacitance with increasing frequency values.Öğe Characterization of an Au/n-Si photovoltaic structure with an organic thin film(Elsevier, 2013-08) Özaydın, Cihat; Akkılıç, Kemal; İlhan, Salih; Rüzgar, Şerif; Güllü, Ömer; Temel, HamdiWe demonstrate that a copper(II) organic complex can control the electrical characteristics of conventional Au/n-Si metal-semiconductor (MS) contacts. We investigated the electronic and photovoltaic properties of a Cu(II) complex/n-Si heterojunction diode. The ideality factor n and barrier height Φb of the diode were 2.22 and 0.736 eV, respectively. An ideality factor greater than unity indicates that the diode exhibits non-ideal current-voltage behavior. This behavior results from the effect of series resistance and the presence of an interfacial layer. The series resistance and barrier height determined using Norde's method were 6.7 kΩ and 0.77 eV, respectively. The device showed photovoltaic behavior, with a maximum open-circuit voltage of 0.24 V and a short circuit current of 1.7 μA under light of 8 mW/cm2.Öğe High barrier Schottky diode with organic interlayer(Elsevier, 2012-03) Güllü, Ömer; Aydoğan, Şakir; Türüt, AbdülmecitA new Cu/n-InP Schottky junction with organic dye (PSP) interlayer has been formed by using a solution cast process. An effective barrier height as high as 0.82 eV has been achieved for Cu/PSP/n-InP Schottky diodes, which have good currentvoltage (IV) characteristics. This good performance is attributed to the effect of formation of interfacial organic thin layer between Cu and n-InP. By using capacitancevoltage measurement of the Cu/PSP/n-InP Schottky diode the diffusion potential and the barrier height have been calculated as 0.73 V and 0.86 eV, respectively. From the IV measurement of the diode under illumination, short circuit current (I sc) and open circuit voltage (V oc) have been extracted as 0.33 μA and 150 mV, respectively.
