Browsing by Author "Nizamoglu, S."

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    ArticlePublicationOpen Access
    Colloidal aluminum antimonide quantum dots
    (American Chemical Society, 2019-07-09) Jalali, H. B.; Sadeghi, S.; Şahin, M.; Öztürk, Hande; Ow-Yang, C. W.; Nizamoglu, S.; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk
    AlSb is a less studied member of the III–V semiconductor family, and herein, we report the colloidal synthesis of AlSb quantum dots (QDs) for the first time. Different sizes of colloidal AlSb QDs (5 to 9 nm) were produced by the controlled reaction of AlCl3 and Sb[N(Si(Me)3)2]3 in the presence of superhydride. These colloidal AlSb quantum dots showed excitonic transitions in the UV-A region and a tunable band-edge emission (quantum yield of up to 18%) in the blue spectral range. Among all III–V quantum dots, these quantum dots show the brightest core emission in the blue spectral region.
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    High brightness illumination based on laser light diffusion with mie scattering
    (ASME, 2022) Azarifar, Mohammad; Cengiz, Ceren; Ocaksönmez, Kerem; Onal, A.; Nizamoglu, S.; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet; Azarifar, Mohammad; Cengiz, Ceren; Ocaksönmez, Kerem
    Limited luminous flux per wafer area of light emitting diodes (LEDs) for high power solid state illumination causes some packaging real estate issues. This problem can be tackled with laser diodes (LDs). At high current densities, LDs offer higher efficiency, however with very low etendue and divergent angle. This significantly increases the complexity of color conversion for white light generation. Concentrated light can carbonize the color conversion unit and have high speckle contrast. These problems can be addressed by efficient diffusion of the laser beam and this paper is aimed to introduce the first laser diffusion system based on TiO2 Mie particles. Based on a series of ray tracing simulations, an idealized cost-effective system is modeled and results showed an almost lossless diffusion with a guiding system based on reflection resulting in an almost uniform irradiance level with only 17% power loss. Furthermore, offered design can reduce the challenges for the compact packaging of white LDs by eliminating the heat sink for color conversion coating and enabling a safe light intensity for utilizing quantum dots for color engineering.
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    High quality quantum dots polymeric films as color converters for smart phone display technology
    (IOP Publishing, 2019-03) Sadeghi, S.; Mutcu, Süleyman Efdal; Srivastava, S. B.; Aydindogan, G.; Caynak, S.; Karsli, K.; Melikov, R.; Nizamoglu, S.; Mutcu, Süleyman Efdal
    Quantum dots (QDs) have high potential to fulfill the ever-increasing demands for high-quality displays due to their outstanding size-tunable optical properties, high quantum yield and reduced costs. The synthesis of efficient materials and their integration in uniform and thin polymeric films are necessary for displays. In this study, we synthesized red-and green-emitting Cd-based QDs with quantum yields of 52% and 74%, respectively. Weincorporated quantum dots into the polydimethylsiloxane (PDMS) polymer matrix by using doctor blade technique, which led to polymeric films with 123 mm x 68 mm dimensions for smart phone displays. We fabricated QD-polymeric films having thickness ranging from 100 to 500 mu m to investigate their color conversion and display application performances. By using the large-area QD-polymeric films on blue-emitting backlight unit, the NTSC and sRGB color gamut ratio was measured as 91% and 127%, respectively. Therefore, QD polymeric films show promise for smart phone applications.