arXiv subjects

Mustafa M. Demir

Publications and source records attributed to Mustafa M. Demir.

3 recordsLinked to original sources

arXiv2022

Improvement of Photophysical Properties of CsPbBr$_3$ and Mn$^{2+}$:CsPb(Br,Cl)$_3$ Perovskite Nanocrystals by Sr$^{2+}$ Doping and Their Application in White-LEDs

All-inorganic lead halide perovskite nanocrystals (NCs) show potential in optoelectronic devices, though their stability and efficiency have yet to improve. In this work, we explore the effect of bivalent metal site doping on the optoelectronic properties of CsPbX$_3$ (X = Br, Cl) perovskite NCs. First, the Pb$^{2+}$ ions in pristine CsPbBr$_3$ NC are partially substituted by Mn$^{2+}$ ions, and the alkaline earth metal strontium is then doped on both pristine and Mn$^{2+}$-substituted particles. The structural and photophysical properties of the pristine and the three doped NC variants have been investigated experimentally as well as exploiting first principles calculations. We found that a small percentage of Sr$^{2+}$-doping improved the photoluminescence quantum yield of the pristine particle by 8%, while it improved the Mn$^{2+}$-state emission by 7%. Perovskite NC film/poly(methyl methacrylate) composites with all four NC variants were used in a white light-emitting diode (WLED) and again both Sr$^{2+}$ doped NCs were found to increase the luminous efficiency of the WLED by ca 4 %. We attribute this performance enhancement to a reduced defect density as well as an attenuated microstrain in the local NC structure.

physics.app-ph↗

arXiv2021

Characterization of Sb scaling and fluids in saline geothermal power plants: A case study for Germencik Region (Büyük Menderes Graben, Turkey)

Turkey is located on the seismically active Alpine-Himalayan belt. Although tectonic activity causes seismicity in the Anatolian plate, it also constitutes an important geothermal energy resource. Today, geothermal energy production is heavily concentrated in Turkey's Western Anatolia region. Graben systems in this region are very suitable for geothermal resources. The Büyük Menderes Graben (BMG) is an area of complex geology with active tectonics and high geothermal potential power. Germencik (Aydin) is located in the BMG, where the geothermal waters include mainly Na-Cl-HCO3 water types. This study examined the stibnite scaling formed in the preheater system of the Germencik Geothermal Field (GGF). The formation of the stibnite scaling on the preheater system dramatically reduces the energy harvesting of the GGF. Considering the stibnite scaling in the surface equipment, the optimum reinjection temperature was determined as 95 $^\circ$C to prevent stibnite scaling in the GGF.

physics.geo-ph↗

arXiv2019

Green Fabrication of Lanthanide doped Hydroxide-based Phosphors: Y(OH)3:Eu3+ Nanoparticles for White Light Generation

Phosphors serve as color conversion layers to generate white light with varying optical features including CRI, CCT, and luminous efficacy. However, they have been produced in harsh synthesis conditions such as high temperature, high pressure, and/or employing a huge amount of solvents. In this work, facile, water-based and a rapid method has been proposed to fabricate lanthanide doped hydroxide-based phosphors. In this sense, submicrometer-sized Y(OH)3:Eu3+ particles, as red phosphor, were synthesized in water at ambient conditions in <60 min reaction time. The doping ratio is controlled from 2.5 to 20% in terms of mole. Meanwhile, first principle calculations were also performed on Y(OH)3:Eu3+ to understand the preferable doping scenario and its optoelectronic properties. As an application, these fabricated red phosphors were integrated into PDMS/YAG:Ce3+ composite to generate white light. The resulting white light showed a remarkable improvement (~24%) for LER, a slight reduction of CCT (from 3900K to 3600K), and an unchanged CRI (~60) as the amount of Y(OH)3:Eu3+ increases.

cond-mat.mtrl-sci↗