Browsing by Author "Genc, Aziz"

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Green fabrication of lanthanide-doped hydroxide-based phosphors: Y(OH)₃:Eu³⁺ nanoparticles for white light generation
(Beilstein-institut, 2019) Guner, Tugrul; Kus, Anilcan; Ozcan, Mehmet; Genc, Aziz; Sahin, Hasan; Demir, Mustafa M.
Phosphors can serve as color conversion layers to generate white light with varying optical features, including color rendering index (CRI), high correlated color temperature (CCT), and luminous efficacy. However, they are typically produced under harsh synthesis conditions such as high temperature, high pressure, and/or by employing a large amount of solvent. In this work, a facile, water-based, rapid method has been proposed to fabricate lanthanide-doped hydroxide-based phosphors. In this sense, sub-micrometer-sized Y(OH)(3):Eu3+ particles (as red phosphor) were synthesized in water at ambient conditions in <= 60 min reaction time. The doping ratio was controlled from 2.5-20 mol %. Additionally, first principle calculations were 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 a PDMS/YAG:Ce3+ composite and used to generate white light. The resulting white light showed a remarkable improvement (approximate to 24%) in terms of luminous efficiency, a slight reduction of CCT (from 3900 to 3600 K), and an unchanged CRI (approximate to 60) as the amount of Y(OH)(3):Eu3+ was increased.
Optimization and performance of nitrogen-doped carbon dots as a color conversion layer for white-LED applications
(Beilstein-institut, 2019) Guner, Tugrul; Yuce, Hurriyet; Tascioglu, Didem; Simsek, Eren; Savaci, Umut; Genc, Aziz; Demir, Mustafa M.
In this study, green-emitting nitrogen-doped carbon dots (N-CDots) were synthesized and incorporated into drop-cast composite films for use as color conversion layers in a white-LED configuration to generate white light. In order to resolve the red deficiency of this configuration, a commercial red phosphor was integrated into the system. Moreover, the N-CDots were also processed into polymer/N-CDot composite fibers, for which we determined the amount of N-CDots that yielded adequate white-light properties. Finally, we showed that white light with excellent properties could be generated by employing both of the fabricated N-CDot composites either as drop-cast films or composite fibers. Hence, N-CDots provide a promising alternative to inorganic phosphors that are commonly employed in white-LED configurations.
Polarized emission from CsPbBr₃ nanowire embedded-electrospun PU fibers
(Iop Publishing Ltd, 2018) Guner, Tugrul; Topcu, Gokhan; Savaci, Umut; Genc, Aziz; Turan, Servet; Sari, Emre; Demir, Mustafa M.
Interest in all-inorganic halide perovskites has been increasing dramatically due to their high quantum yield, band gap tunability, and ease of fabrication in compositional and geometric diversity. In this study, we synthesized several hundreds of nanometer long and similar to 4 nm thick CsPbBr3 nanowires (NWs). They were then integrated into electrospun polyurethane (PU) fibers to examine the polarization behavior of the composite fiber assembly. Aligned electrospun fibers containing CsPbBr3 NWs showed a remarkable increase in the degree of polarization from 0.17-0.30. This combination of NWs and PU fibers provides a promising composite material for various applications such as optoelectronic devices and solar cells.